Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 13287~2 RK353 FF
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~ DESCRIPTION
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Conductive Polymeric Article
This invention relates to an article which comprises a
conductive polymeric material, which can be heated by
passing electrical current through the conductive polymeric
material.
Conductive polymeric materials and devices incorporating
them are also well known. Reference may be made for example
U.S. Patents Nos. 2,952,761, 2,978,665, 3,243,753,
3,351,882, 3,571,777, 3,658,976, 3,757,086, 3,79~,716,
3,823,217, 3,858,144, 3,861,029, 3,950,604, 4,017,715,
4,072,848, 4,085,286, 4,117,312, 4,151,126, 4,177,376,
4,177,446, 4,188,276, 4,237,441, 4,242,573, 4,246,468,
4,250,400, 4,252,692, 4,255,698, 4,271,350, 4,272,471,
4,304,987, 4,309,596, 4,309,597, 4,314,230, 4,314,231,
4,315,237, 4,317,027, 4,318,881, 4,327,351, 4,330,704,
4,334,351, 4,352,083, 4,361,799, 4,388,607, 4,398,084,
4,413,301, 4,425,397, 4,426,339, 4,426,633, 4,427,877,
4,435,639, 4,429,216, 4,442,139, 4,459,473, 4,470,898,
4,481,498, 4,476,450, 4,502,929; 4,514,620, 4,517,449,
4,534,889, and 4,560,498; J. Applied Polymer Science 19,
813-815 (1975), Rlason and Kubat; Polymer Engineering and
Science 18, 649-653 (1978), Narkis et al; European ~6~1S~e~
Application Nos. 38,713, 38,714, 38,718, 74,281, 92,406,
119,807, 133,748, 134,145, 144,187, 157,640, 158,410,
175,550 and 176,284; and Japanese Published Patent
Application No. 59-122,524.
We have discovered a new conductive polymeric article
which can be heat recoverable and used as a heat recoverable
cover, and/or can be an electrically powered article.
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heat-recoverable article is an article the dimensional
configuration of which may be made subtantially to change
when subjected to heat treatment. Usually these articles
recover, on heating, towards an original shape from which~
they have previously been deformed, but the term
"heat-recoverable", as used herein, also includes an article
which, on heating, adopts a new configuration, even if it
has not been previously deformed.
Heat recoverable articles are known. In their most com-
mon form, such articles comprise a heat-shrinkable sleeve
made from a polymeric material exhibiting the property of
elastic or plastic memory as described, for example, in U.S.
Patents 2,027,962, 3,086,242 and 3,597,372. As is made clear
in, for example, V.S. Patent 2,027,962, the original dimen-
sionally heat-stable form may be a transient form in a con-
tinuous process in which, for example, an extruded tube is
expanded, whilst hot, to a dimensionally heat-unstable form.
In other applications, a preformed dimensionally heat stable
article is deformed to a dimensionally heat unstable form in
a separate stage.
In other articles, an elastomeric member is held in a
stretched state by a second member, which, upon heating
weakens and thus allows the elastomeric member to recover.
Heat-recoverable articles of this type are described, for
example, in British Patent 1,440,524 in which an outer tubu-
lar elastomeric member is held in a stretched state by an
inner tubular member. Alternatively, the "hold-out" layer
could be on the outside.
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Heat-recoverable articles which comprise conductive
polymeric materials, and which use ohmic heating of those
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materials to cause heat recovery are also known. Referencemay be made for example to GB 1265194 (MP099 ~, US 4085286
(MP192), US 401771S (MP0212), US 4421582 (MP0219), European
Patent Publication No. 0157640 (MP0922) and US 4570055
(MP0939) .
It is also known to be desirable to use for a conductive
recoverable article, a material which exhibits a PTC
(positive temperature coefficient of resistivity) effect,
that is a sharp rise in resistivity at a particular, or over
a short range of temperatures. This temperature or tem-
perature range is known as the anomaly or switching tem-
perature. Typically the material is selected to exhibit the
sharp rise in temperature at or slightly above the recovery
temperature of the article. The PTC effect minimises
overheating and consequent so-called "thermal runaway" of
the material. Materials which exhibit a PTC effect are
typically referred to simply as PTC materials.
An article according to the invention is tubular and has
elongate electrodes extending along its length which when
connected to a source of electrical power causes electrical
current to flow between the electrodes around the circum-
ference of the article. In order to heat and/or recover
selected parts only of the article, the electrode (which
extends along the entire length of the article) may be
interrupted.
Thus, a first aspect of the invention provides a tubu-
lar article comprising conductive polymeric material having
two or more elongate electrodes extending at least part way
along the length of the article, at least one of which
elongate electrodes is interrupted so that an electrical
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` power source can be selectively connected to the article to
cause electrical current to pass through a first length only
of the article.
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More particularly, the first aspect of the invention
~ provides a radially heat-shrinkable tubular article which
- comprises (1) a component comprising a conductive polymer,
and (2) at least three elongate electrodes positioned so that
(i) each of the electrodes extends at least part of the way
along the length of the conductive polymer, (ii) at least two
` of the electrodes are spaced from each other longitudinally,
and (iii) at least two of the electrodes are
` circumferentially spaced from one or more of the other
electrodes so that (a) a first set of two or more selected
electrodes can be connected to a suitable electrical power
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source and thus cause electrical current to pass in a
circumferential direction through a first part only of the
component, and to generate heat within that first part which
causes radial shrinkage along a first length of the article
20 only; and (b) a second set of two or more selected electrodes
can be connected to a suitable electrical power source and
thus cause electrical current to pass in a circumferential
direction through a second part only of the component and to
generate heat within that second part.
The term "interrupted" means that there is a
discontinuity in the length of the electrode. The
interrupted electrode may have been made by starting with a
longer continuous electrode and removing part of its length
30 (other than at one end). Alteratively the "interrupted"
electrode may be made by applying two discrete electrode
- lengths. There is no direct, low resistance, electrical
connection between the parts of the interrupted electrode.
Tubular articles according to the invention may be of
open (wraparound) or closed cross-section. When tubular
articles are used they may be open at one or both ends.
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As used herein the term "wraparound" means a cover which
can be wrapped around a substrate, with longitudinal edgec
secured together to form a tubular article around the
substrate. The term does not include wrapped tape.
A feature of this article is that it can be made in a
continuous process in long lengths and then later cut to the
desired length.
The above arrangement enables the first length of the
interrupted electrode(s), on one side of the interruption, to
be connected to a source of electrical power independently of
the remaining part of the electrode. Several interruptions
may be made in the electrodes if desired. This invention is
advantageous where it is desirable to heat or recover only
one part of the tubular article, or where it is desired to
heat or recover that portion at a different time.
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For example, one part of an article may be heated to
; activate or cure an underlying adhesive or sealant before a
second part is heated. one or more parts of the article can
; be used to deliver adhesive or sealant to an area before
another part of the article is heated.
The article according to the invention may be expanded
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` to render it recoverable or it may be non expanded, and hence
heat-stable. Thus the article may be a recoverable cover
~ 10 and/or heater or a heat stable heater.
; Canadian Patent Application 576,762 (DK003 CA) describes
~ a heat recoverable article (preferably tubular) which
; comprises electrically conductive recoverable material, and
is provided with at least two integrally formed spaced apart
support elements. The support elements also comprise
electrically conductive material and are dimensionally heat
stable, so that they remain undeformed during recovery, other
than bending to accommodate transitions. The arrangement
ensures good contact is maintained throughout recovery of the
article. This arrangement is suitable for use in the present
invention, the electrodes (which are interrupted, or are to
be interrupted) being positioned on or in the support
elements, which are typically in the form of elongate
flanges.
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Canadian Patent Application 576,763 (DK004 CA) describes
a heat recoverable conductive polymeric, preferably tubular,
article with longitudinal electrodes extending part way only
along its lçngth.
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Canadian Patent Application 576,671 filed
; contemporaneously herewith, discloses articles comprising a
material with specific electrical properties to control the
~`' direction of current flow. One article according to Canadian
Patent Application No. 576,671 has been expanded from X% to
Y% to make it heat recoverable, the article comprising a
conductive polymeric material the resistivity of which
decreases on expansion, as measured in the direction of
current flow, in at least part of the X - Y% expansion range.
Another article according to the invention is heat
recoverable and comprises a conductive polymeric material
which has a resistivity which increases on recovery, as
measured in the direction of current flow, throughout the
temperature range 20C to Te (extrapolated end temperature,
as measured according to ASTM D3418-82).
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Other articles according to that invention have a so-
called pseudo-PTC ratio (peak resistivity: resistivity at
25C in the range 1~ to 10, and are connected to electrodes
so that current flows parallel to the faces of the article.
Preferred articles are expanded to render them recoverable
and the resistivity of the composition of the articles
~ decreases in at least part of the expansion range when
; expanded by 25% or more, for example by 25 - 500%.
Canadian Patent Application 576,766 (RK352-A CA)
describes a tubular article which comprises a conductive
polymeric material and is preferably heat recoverable and
which can apply a radially inward force on a substrate
therein. This can be used to join or repair a substrate e.g.
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` ~28722
a cable or a pipe. It can, for example, melt a polymeric
patch between the article and the substrate. It is
preferably multi-part or wraparound, for easy installation.
Canadian Patent Application 576,764 (DKO06 CA )
describes a tubular conductive polymeric article which has
particular application as a duct seal, and which increases in
thickness on recovery. It preferably has three longitudinal
sections, which are all electroded separately. The end
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sections shrink radially, and the central section increases
- in thickness. According to the present invention, the
longitudinal sections may comprise interrupted elongate
electrodes.
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The interrupted electrodes of the present invention may
be used in any of the above described articles.
As mentioned above, in preferred embodiments the
electrodes are provided in or on longitudinal flanges
extending along the length of the article. Such an arrange-
ment is described in Canadian Patent Application No. 576,762
(DK003 CA). In these cases the interruption in
the electrodes is preferably effected by making a cut through
the flanges and associated electrodes, so that there is an
electrically insulating space between the cut ends of the
electrode.
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A second aspect of the invention provides a method of
making a selectively heatable or selectively recoverable
~ tubular article comprising:
;~ 5 (a) forming a tubular article comprising conductive
', polymeric material,
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ii (b) providing two or more longitudinal electrodes
extending along the article,
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;'3 (C) interrupting the electrical continuity of at least.~ one electrode, thereby defining a first electrodepart which can be connected to an electrical power
source and a remaining electrode part which can be
separately connected to an electrical power source.
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More particularly, the second aspect of the invention
provides:
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A method of making a selectively heatable tubular
-~ 5 article comprising : (a) providing a tubular article which
comprises a component comprising a conductive polymer and at
least two spaced-apart elongate electrodes, each of which
extends at least part way along the length of the component,
and (b) interrupting the electrical continuity of at least
. 10 one of the electrodes, thereby defining a first electrode
which can be connected to an electrical power source and a
. second electrode which is spaced apart from the first electrode, and which can be separately connected to an
electrical power source.
A method of providing a covering on a substrate which
comprises (A) providing a substrate and, around the
'5~, substrate, a radially heat-shrinkable tubular article which
comprises: (1) a component comprising a conductive polymer
and (2) at least three elongate electrodes positioned so that
. (i) each of the electrodes extends at least part of the way
along the length of the conductive polymer, (ii) at least two
. of the electrodes are spaced from each other longitudinally,
and (iii) at least two of the electrodes are
. 25 circumferentially spaced from one or more of the other
:^` electrodes; (B) connecting a first set of two or more
selected electrodes to an electrical power source, thereby
A,, causing electrical current to pass in a circumferential
direction through a first part only of the component, and to
: 30 generate heat within the first part which causes a first
length of the article to shrink radially towards the substrate; and (C) before, during or after step (B)
~r connecting a second set of two or more selected electrodes to
an electrical power source, thereby causing electrical
current to pass in a circumferential direction through a
second part only of the component and to generate heat within
the second part.
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In a preferred embodiment the tubular article is pro-
vided with longitudinal conductive polymeric flanges
extending along at least part of the length of the article,
and the electrodes are provided in or on these flanges. In
this case the electrical continuity of the electrode(s) may
be interrupted, for example, by cutting and removing a sec-
tion of each flange, part-way along the length of the
electrode(s). Where the electrodes are provided on the sur-
face of the flanges or the surface of the body of the
article, e.g. by silver conductive ink or paint, they may be
~A mechanically removed, e.g. by abrading.
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As an alternative the electrodes may be provided
interrupted in the first instance. Thus a third aspect of
the invention provides a selectively heatable or selectively
~A recoverable tubular article comprising:
(a3 a tubular article comprising conductive polymeric
material, and
(b) three or more longitudinal electrodes extending
along the article, at least two or which extend
i along the same line but are separated from each
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other.
The two electrodes that are separated from each other
~- may nonetheless be electrically connected via a higher
~~ resistivity medium (ie the conductive polymeric material of
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the main body of the article). There is however no direct
low resistance electrical connection between the electrodes.
Also there may be a mass of insulating material between the
separated electrodes.
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1328722
The invention also provides a method of making this
article comprising providing the constituent parts thereof.
A fourth aspect of the invention provides a method of
using the article according to the second and third aspects
of the invention for independently heating/recovering the
separated sections. Thus this aspect provides a method of
selectively heating or recovering a tubular article,
comprising connecting the said first part of each electrode
to cause current to flow between said first parts, and
optionally separately connecting the remaining parts, of each
electrode to an electrical power source to cause electrical
current to flow between said remaining electrode parts.
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The concept of independently electroding and
heating/recovering different sections of a conductive
polymeric article is believed novel ~er se. This may be done
with longitudinal electrodes as described with reference to
aspects one, two and three of the present invention.
Preferred compositions for use in the present invention
` are described in Canadian Patent Application 516,760 (RK365
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One material that can be used is 59.4 parts by weight
;- Elvax 460 (an E.V.A. of 18% by weight vinyl acetate content
and a melt flow index of 2.5, as supplied by Du Pont), 39.6
~ parts by weight of Vulcan P (a carbon black supplied by Cabot
s Corporation) and 1 part by weight antioxidant. Other
suitable examples are:
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Polymer Carbon Black Antioxidant
(parts by weight) (parts by weight) (parts by weight)
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- Marlex* ~XM 50100 (59.4) Vulcan * P (39.6) (1.0)
Elvax * 460 (59.4) Sevalco* N110 (39.6) (1.0)
Sclair* llD-l (59.4) Ensaco* MS (39.6) (1.0)
Elvax* 770 (59.4) Vulcan* P (39.6) (1.~)
`~ * represents a trademark.
The polymeric materials used as follows:
- Marlex is a HDPE supplied by Phillips
Elvax 460 - described earlier
Sclair llD-l is a LLDPE supplied by Du Pont, Canada
Elvax 770 is an EV~ supplied by Du Pont.
Vulcan P, Ensaco MS and Sevalco N110 carbon blacks are
supplied by Cabot Corporation, Ensagri Willebroek NV and
`~ Sevalco Ltd respectively.
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.'' One preferred article according to the invention is a
v~ tubular article which has been expanded radially and has two
or more, preferably three separately radially shrinkable
.,
~-l sections. The article preferably comprises longitudinally
' separated pairs of electrodes (one pair for each separately
i radially shrinkable section) arranged to shrink each of the
J~ sections. One example of such an article is for cable
blocking a cable splice, e.g. a splice between optical
fibres. For this application there are three separately
radially shrinkable sections. The central section contains
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a large mass of adhesive or other sealant, for cable
blocking. The end sections are lined with adhesive, e.g. a
hot melt adhesive, for bonding to ~he cables.
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For cable blocking and similar applications, there is
not necessarily a requirement for the inner surface of the
article to be smooth (since the substrate may not be). Thus
in the preferred case where the electrodes a-re provided-on
heat stable flanges projecting from the surface of the
article (as described in British Patent Application 8810522
(DK003 GB5) these flanges may project outwardly from or
inwardly into the article, or both.
Another preferred article, which is recoverable, compri-
ses a conductive polymeric hold-out layer which holds in a
stretched state an elastomeric layer. The hold-out layer
may be the inner or outer layer. The elastomeric layer is
allowed to recover when the conductive layer heats.
Where the article is tubular with one or more open ends,
it may be desirable to seal between two or more substrates
exiting the open end. This can be achieved using a branch-
off clip (e.g. as disclosed in US 4648924) which brings
together circumferentially spaced portions of the walls of
the article between the substrates. Preferably an electri-
cally heated branch-off clip is used. As an alternative an
electrically heated filling piece may be used. The electri-
cally heated clip and filling piece may be powered by the
same power supply that is used to heat and recover the
article.
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f~ In articles according to the invention, the wall
thickness of the article may be varied along its length.
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~` Also two or more layers of different materials may be used.
The second or additional layer may extend along the whole or
along part of the length of the article. They may have
electrical properties e.g. room temperature resistivity and
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resistivity/temperature behaviour, that are the same as, or
different to, that of the first material. As an example, the
second or subsequent layers may comprise a material that
exhibits traditional PTC behaviour or ZTC (~ero temperature
coefficient of resistivity) behaviour. The effect of the
additional layer(s) is that it (they) provide additional
material through which electrical current can flow, and
hence provide additional heating. By appropriate choice of
the resistivity of the material of the additional layer(s)
greater heating can be achieved than would be the case were
a similar additional thickness of the first material used.
This may be advantageous, for example to decrease recovery
times in certain regions, or where a higher temperature is
required. Therefore in some preferred embodiments second or
subsequent layers of material different to the first
material are added in selected regions.
Another example of using two layers of different
materials is where certain properties, e.g. flame retardancy,
solvent resistance, abrasion resistance, electrical insula-
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tion, impact resistance, colour coding are required.
Where two or more layers are used these may be appliedseparately, for example by sequential extrusion or may be
co-extruded.
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The present invention may be ultilised in a variety of
- articles of different shapes. They are generally tubular,
including wraparounds, and may be open at one or both ends.
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- Embodiments of the invention will now be described byway of example with reference to the accompanying drawings
wherein:
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132~722
Figure 1 shows a recoverable article according to the
invention;
Figure 2 shows the article of Figure 1, with separated
electrodes;
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Figure 3 shows the article of Figure 2, one end of which
has been recovery onto a substrate; and
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Referring now to the drawings, Figure 1 shows a tubular
article 2-and comprising a conductive polymeric material.
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The ~ain body of the article has been expanded to make it
recoverable. Electrodes 4 in the form o~ wires 4 extend in
heat stable conductive polymeric flanges 6 along the length
of the article.
Figure 2 shows the article of Figure 1, in which the
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- electrodes have been interrupted by a notch 8. This enables
section 10 (to the left of notch 8 in the drawings) to be
heated/recovered independently of part 12 (to the right of
notch 8 in the drawings.) Notch 8 can be made with a
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" suitable cutting tool.
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The flanges 6 are cut back at one end to bare projecting
1 25 portions 4 which can be connected to a power source 15. As
: an alternative method of contacting the electrodes, insula-
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~;'' tion - displacement type devices could be used.
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Figure 3 shows the article 2' with one end 10' recovered
' 30 onto pipe 16, (superscript indicates recovered part).
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