Note: Descriptions are shown in the official language in which they were submitted.
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RENOVATING PIPELINES
FIELD OF THE INVENTION
THE PRESENT INVENTION relates to a method for the renovation of existing
pipeline
infrastructures. More particularly, the present invention relates to a method
for the renovation of
existing drinking water pipelines by means of the application of a liquid, two
part coating
composition to the internal surface of the pipeline. The method is, however,
also applicable to
pipelines of other kinds.
BACKGROUND OF THE INVENTION
Existing trenchless methods for the structural renovation of drinking water
pipelines rely on the
insertion of a moulded material, such as a polyethylene pipe or liner, inside
an existing pipe. The
three main trenchless technologies employed for this purpose can be summarised
according to the
following:
Pipe in Pipe Method
A moulded (e.g. polyethylene) pipe with a diameter smaller than that of the
existing pipe is either
pulled or pushed into the existing pipe. By virtue of being an extremely
simple method, it has been
used to renovate not only drinking water pipelines, but many other pipeline
infrastructures.
However, the method does have its shortcomings. For example, as insertion
resistance increases over
long spans, the length and complexity of pipes is limited. Furthermore, it is
also necessary to
consider the reduction in supply capacity of a pipe renovated by this method
as a result of the
annular gap between the existing pipe and the internal pipe.
Pipe Bursting Method
The method, as the name implies, is executed by expansion and cracking of the
existing pipe by
insertion of a hydraulic expander inside it, accompanied by insertion of a
moulded polyethylene pipe
into the space thus formed. Benefits of this method are the simplicity of use
and the ability to install
pipes with an equivalent or larger diameter than the existing pipe. However,
disadvantages are the
potential damage to other infrastructures in urban environments, and the
difficulty in disposing of
residual pipe fragments.
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Polyethylene Thin Wall Lining (PETWL)
A folded polyethylene liner is inserted into the existing pipe and pressure
applied to produce a "close
fit" liner, which is subsequently held in place by the water pressure within
the pipeline.
All three of the above methods are disadvantaged by their inability to deal
with multiple bends in a
pipeline and, more importantly, the fact that lateral connection pipes to
customers' premises have to
be disconnected and then reinstated after execution of the renovation process.
A need therefore exists for a renovation method which has the capability to
accommodate long pipe
spans (up to 200 meters) and pipe bends, and which obviates the necessity for
reinstatement of
lateral connection pipes.
SUMMARY OF THE INVENTION
The invention provides a method for the renovation of existing pipelines, such
as drinking water
pipelines, by means of the application of a liquid, two-part coating
composition to the internal
surface of the pipeline so as to form, at high cure rate, a monolithic
flexible lining with high strength
and ductility.
Preferably, the method is carried out by spraying the coating composition onto
the internal surface of
the pipeline from an apparatus which is moved through the pipeline so that the
method of the
invention obviates any need for disconnection and subsequent reinstatement of
lateral connection
pipes.
According to the invention, there is provided a method of forming a coating on
the internal surface
of a pipeline, the method comprising the steps of:
a) providing a liquid, two-part coating system
b) mixing together the first part and the second part to form a mixture, and
c) applying the mixture as a coating to said surface so as to form, at high
cure rate, a monolithic
lining which exhibits high strength and flexibility.
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Preferably the two parts of the system are applied through heated airless
spray equipment. Such
equipment may, for example, include a centrifugal spinning head or a self-
mixing spray gun
assembly.
In a first group of embodiments, the first part of the two-part coating system
comprises an aliphatic
polyisocyanate compound and the second part comprises one or more aromatic
polyamines blended
with one or more polyhydric alcohol compounds.
In a second group of embodiments, the first part again comprises one or more
aliphatic
polyisocyanates, but no polyhydric alcohols are used and instead, appropriate
coating properties are
achieved by selection of the polyisocyanate component used and by close
control of the proportion
of the components used. Thus, in some embodiments of the second group, the
polyisocyanate
comprises an isocyanate prepolymer derived from HDI (hexamethylene di-
isocyanate), for example,
from the uretdione of HDI or from the biuret of HDI or from the isocyanate
trimer of HDI, or from
the isocyanurate of HDI. The aliphatic isocyanate, in this second group of
embodiments, preferably
has an isocyanate content of 5 to 15% by weight.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention provide a two-part coating
system that can be
applied to the internal surfaces of existing pipeline infrastructures so as to
form, at a high cure rate, a
monolithic flexible lining, which exhibits high strength. By virtue of its
strength, flexibility and non-
tainting characteristics, the system of the present invention is particularly
useful for the renovation of
existing drinking water pipelines.
The first part of a two-part coating system, according to both the first and
the second group of
embodiments, of the present invention, comprises one or more aliphatic
polyisocyanates. The first
liquid part may, for example, comprise an aliphatic isocyanate derived from
hexamethylene di-
isocyanate (HDI). Suitable polyisocyanates include derivatives of
hexamethylene-1, 6-diisocyanate;
2,2,4-trimethylhexamethylene diisocyanate; isophorone diisocyanate; and
4,4'dicyclohexylmethane
diisocyanate. For the purposes of the first group of embodiments of the
present invention the
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preferred polyisocyanates are the uretdione, biuret and isocyanurate trimer of
hexamethylene-1,6-
diisocyanate, with the uretdione being particularly preferred.
In the first group of embodiments of the invention, the preferred
polyisocyanates have an isocyanate
content of 15-30%, with an isocyanate content of 20-25% being particularly
preferred.
The second part of a two-part coating system, in this first group of
embodiments of the present
invention, comprises one or more aromatic polyamines blended with one or more
polyhydric alcohol
compounds. The polyhydric alcohol compound may be a branched polyether-ester
polyol, for
example having a hydroxyl content of 2-10%.
Suitable aromatic polyamines include diethyl toluenediamine; dimethylthio
toluenediamine; 4,4'-
methylenebis (2-isopropyl-6-methylaniline); and
4,4'-methylenebis (3-chloro-2,6-diethylaniline). For the purposes of the
present invention, diethyl
toluenediamine is particularly preferred.
The polyhydric alcohol compounds can be polyester or polyether polyols
containing at least two
hydroxyl groups per molecule. For the purposes of the present invention,
branched polyether-esters
are particularly preferred. The preferred polyols have a hydroxyl content of 2-
10%, with a hydroxyl
content of 4-8% being particularly preferred.
In order to accelerate the reaction between the polyol and the polyisocyanate,
the second part of the
coating system may optionally contain a suitable catalyst. A number of organo-
metallic compounds
may be used, however for the purposes of the present invention, tin compounds
are preferred, with
dibutyltin dilaurate and dimethyltin carboxcylates being particularly
preferred.
As noted, the first part of a two-part coating system, in the second group of
embodiments of the
present invention, again comprises one or more aliphatic polyisocyanates.
Again, the first liquid part
may, for example, comprise an aliphatic isocyanate derived from hexamethylene
di-isocyanate
(HDI). Suitable polyisocyanates again include derivatives ofhexamethylene-1, 6-
diisocyanate; 2,2,4-
trimethylehexamethylene diisocyanate; isophorone diisocyanate; and 4,4'
dicyclohexylmethane
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diisocyanate. For the purposes of the second group of embodiments of the
present invention, the
preferred polyisocyanates are prepolymers derived from hexamethylene-1,6-
diisocyanate (HDI) or
prepolymers derived from the dimeric or trimeric forms of HDI. Thus, the
polyisoCyanate may
comprise a prepolymer derived from the uretdione or the biuret of HDI, or from
the isocyanurate
trimer of HDI. Where such a prepolymer is used, the prepolymer may be blended
with the uretdione
of HDI, or with the biuret of HDI, or with the isocyanurate trimer of HDI, in
any combination. The
preferred isocyanate prepolymers have an isocyanate content of 5-15%, with an
isocyanate content
of 8-12% being particularly preferred.
The second part of the two-part coating system, according to the second group
of embodiments of
the invention again comprises one or more aromatic polyamines, but in this
case without polyhydric
alcohols. Suitable aromatic polyamines again include diethyl toluendiamine;
dimethylthio
toluendiamine; 4,4' - methylenebis (2-isoproppyl-6-methylaniline); 4,4' -
methylenebis (2,6 -
diisopropylaniline); 4,4'- methylenebis (2-ethyl-6-methylaniline); and 4,4'
methylenebis (3-chloro-
2,6-diethylaniline). For the purposes of the present invention, diethyl
toluenediamine is particularly
preferred.
A number of two-part systems embodying the invention are described below, by
way of non-limiting
example with reference to Tables 1 to 9 which form the accompanying drawings,
and in which:
Table 1 identifies various two part systems in accordance with a first group
of embodiments of the
invention,
Tables 2 and 3 set out properties of the respective systems,
Table 4 sets out further two-part systems, of which at least those indicated
at L to R are in
accordance with the first aspect of the invention,
Tables 5 and 6 set out properties of the respective systems of Table 4,
Tables 7 and 8 identify various two-part systems in accordance with a second
group of embodiments
of the invention, and
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Table 9 sets out properties of the systems of Tables 7 and 8.
In carrying out the method of the invention, the first and second parts of the
system are fed
independently, e.g. by flexible pipelines, to a spraying apparatus, known per
se, capable of being
propelled through an existing pipeline to be renovated. The apparatus
preferably heats the two parts
of the system prior to application to the pipeline interior and mixes the two
parts immediately before
applying the mixture to the interior surface of the pipeline. The mixture of
the two parts cures on the
interior surface of the pipeline to fonn a flexible impervious coating.
In view of the confined spaces within the pipeline and the resultant lack of
suitable outlet for vapour,
both the first part and the second part of the system, in each case, are free
of any volatile solvent.
That is to say, solidification of the system applied to the pipeline interior
is in no way a result of
drying or evaporation of solvent from either part of the system.
EXAMPLES
Referring firstly to Tables 1 to 6, in each of the examples illustrated
therein, the first part of the
system comprises an isocyanate, for example DESMODUR N3400, as indicated by
the following
brief notes referring to the Tables, whilst the second part of the system
comprises a blend of the
components indicated in the first three columns to the left of each table. In
each of Tables 1 and 4,
the column at the extreme right indicates the amount of the isocyanate first
part used. The quantities
indicated in Tables 1 and 4 are parts by weight.
Table 1 shows the composition of a number of coating systems prepared from
binary and ternary
mixtures comprising an aromatic polyamine (Ethacure 100), selected oligomeric
polyamines and a
secondary aliphatic polyamine (Amine SDA 172), cured with Desmodur N3400 at an
isocyanate
index of 1Ø
Table 2 shows the physical properties of the coating systems detailed in Table
1. It can be seen from
the tensile and flexural properties of these systems that they possess the
combination of strength and
ductility that could render them useful as rapid setting pipeline renovation
materials.
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Table 3 shows the results of a series of screening tests carried out on the
coating systems detailed in
Table 1 in order to assess their likely suitability for contact with drinking
water. It can be seen from
these results that whilst all the systems satisfy the Flavour & Odour element
of the BS6920
Suitability for Contact with Potable Water test, the T.O.C (total organic
carbon) figures suggest that
the materials would be unlikely to gain the necessary regulatory approvals for
use in contact with
public water supplies.
Table 4 details the composition of a number of coating systems prepared from
binary mixtures
comprising an aromatic polyamine (Ethacure 100) and selected branched
polyether-ester polyols
cured with Desmodur N3400 at an isocyanate index of 1.0, and catalysed with
Fomrez UL-28 (0.5
pbw per 100 of polyol).
Table 5 shows the physical properties of the coating systems detailed in Table
4. Again it can be
seen from the tensile/flexural properties of these systems that they could
potentially be useful as
rapid setting pipeline renovation materials.
Table 6 shows the results of a series of screening tests undertaken on the
coating systems detailed in
Table 4, in order to assess their likely suitability for contact with drinking
water. A number of the
systems satisfy the requirements of the Flavour & Odour element of BS6920,
and, furthermore,
afford T.O.C figures such that they would be likely to gain the required
regulatory approvals for use
in contact with public water supplies.
Referring now to Tables 7 to 9, in Table 7, further examples are illustrated,
in each of which the first
part of the system again comprises an isocyanate (Desmodur N3400 and/or
Desmodur N3800),
whilst the second part of the system comprises an aromatic polyamine (diethyl
toluenediamine) in
these examples, (Ethacure 100).
TABLES
Table 1 shows the composition of a number of coating systems prepared from
binary and ternary
mixtures comprising an aromatic polyamine (Ethacure 100), selected oligomeric
polyamines and a
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secondary aliphatic polyamine (Amine SDA 172), cured with Desmodur N3400 at an
isocyanate
index of 1Ø
Table 2 shows the physical properties of the coating systems detailed in Table
1. It can be seen from
the tensile and flexural properties of these systems that they possess the
combination of strength and
ductility that could render them useful as rapid setting pipeline renovation
materials.
Table 3 shows the results of a series of screening tests carried out on the
coating systems detailed in
Table 1 in order to assess their likely suitability for contact with drinking
water. It can be seen from
these results that whilst all the systems satisfy the Flavour & Odour element
of the BS6920
Suitability for Contact with Potable Water test, the T.O.C (total organic
carbon) figures suggest that
the materials would be unlikely to gain the necessary regulatory approvals for
use in contact with
public water supplies.
Table 4 details the composition of a number of coating systems prepared from
binary mixtures
comprising an aromatic polyamine (Ethacure 100) and selected branched
polyether-ester polyols
cured with Desmodur N3400 at an isocyanate index of 1.0, and catalysed with
Fomrez UL-28 (0.5
pbw per 100 of polyol).
Table 5 shows the physical properties of the coating systems detailed in Table
4. Again it can be
seen from the tensile/flexural properties of these systems that they could
potentially be useful as
rapid setting pipeline renovation materials.
Table 6 shows the results of a series of screening tests undertaken on the
coating systems detailed in
Table 4, in order to assess their likely suitability for contact with drinking
water. A number of the
systems (identified by the letters L, M, N and P) satisfy the requirements of
the Flavour & Odour
element of BS6920, and, furthermore, afford T.O.C figures such that they could
be considered
candidates for use in contact with public water supplies. However, a series of
screening tests on
selected coating systems (system L, M, N &P) detailed in Table 4, in order to
further assess their
likely suitability for contact with public water supplies, showed that whilst
all of these systems
appeared promising in terms of BS6920 and T.O.C test results, leachate samples
produced from all
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these compositions exhibited the presence of a number of
unknown/unidentifiable compounds when
examined by GCMS techniques, such that these compositions (L, M, N & P), could
be considered
unlikely to gain the regulatory approvals for contact with public drinking
water supplies.
Table 7 shows the composition of a number of coating systems (identified by
letters S, T, V & W)
prepared from a prepolymer derived from the isocyanurate trimer of HDI
(Desmodur N3800),
blended with the uretdione of HDI (Desmodur N3400) and cured with an aromatic
polyamine
(Ethacure 100) at an isocyanate index of 1Ø
Table 8 shows the physical properties of the coating systems detailed in Table
7. It can be seen
from the tensile and flexural properties of these systems that they possess a
combination of strength
and ductility which could render them useful as rapid setting pipeline
renovation materials.
Table 9 shows the results of a series of screening tests undertaken on the
coating systems detailed in
Table 7 in order to assess their likely suitability for contact with drinking
water. From the results, it
can be concluded that these systems would be likely to gain the required
regulatory approvals for use
in contact with public water supplies.
The chemical identities of the various materials referred to herein by trade
names and Registered
Trade Marks, as well as sources for these materials, can be ascertained by
reference to the following
"Glossary of Materials and Test Procedures".
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GLOSSARY OF MATERIALS AND TEST PROCEDURES
ETHACURE 100 - Diethyl toluenediamine : Albermarle Corporation
JEFFAMINE D2000 - Poly (oxypropylene) diamine,
approx. 2000 molecular weight : Huntsman
VERSALINK P-650 - Poly (oxytetramethylene)-di-p- aminobenzoate, approx. 800
molecular weight : Air Products and Chemicals Inc.
AMINE SDA 172 - N,N'-di-tert-butylethylenediamine Nitroil GmbH
DESMOPHEN 1145 - Branched polyether-ester polyol, hydroxyl content approx.
7.2%: Bayer
DESMOPHEN 1150 - Branched polyether-ester polyol, hydroxyl content approx.
5.4% : Bayer
SOVERMOL 805 - Branched polyether-ester polyol, hydroxyl content approx.
5.4%: Cognis GmbH
SOVERMOL 815 - Branched polyether-ester polyol, hydroxyl content approx.
6.0% : Cognis GmbH
FOMREZ UL-28 - Dimethyltin carboxylate : Witco GmbH
DESMODUR N3400 - Uretdione of hex amethyl ene- 1,6-diisocyanate, isocyanate
content approx. 22% : Bayer
DESMODUR N3800 - Flexibilising trimer of hexamethylene - 1,6- diisocyanate,
isocyanate content approx. 11 %: Bayer
Tensile Properties - BS EN ISO 527:1996
Flexural Properties - BS EN ISO 178:1997
Flavour & Odour - BS 6920, 2.2.3:2000
T.O.C - 24 hour stagnation, lml water/cm2
GCMS General Survey- 24 hour stagnation, 1 ml water/cm2
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Table 1:
COMPOSITION (pbw)
SYSTEM
JEFFAMINE VERSALINK DESMODUR
ETHACURE 100 D2000 P-650 Amine SDA 172 N3400
A 30 70 - 75
B 40 60 - - 95
C 20 - 80 - 80
D 30 - 70 - 95
E 30 35 35 - 85
F 40 30 30 - 105
G 30 60 - 10 95
H 40 50 - 10 115
Table 2:
SYSTEM FILM SET TIME TENSILE ELONGATION FLEXURAL
At 3mm (Mins) STRENGTH AT BREAK STRENGTH
(Mpa) (%) (Mpa)
A 1.5 26.0 50 37.0
B 1.5 28.0 40 42.0
C 2.5 26.0 20 34.0
D 2.5 30.0 15 40.0
E 2 28.0 40 40.0
F 2 31.0 30 42.0
G 3 27.0 50 37.0
H 3 28.0 40 41.0
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Table 3:
BS 6920 T.O.C
SYSTEM FLAVOUR & ODOUR (mg/Litre)
A PASS 5.4
B PASS 5.1
C PASS 6.3
D PASS 6.0
E PASS 5.9
F PASS 5.9
G PASS 6.0
H PASS 6.2
Table 4:
COMPOSITION (pbw)
SYSTEM
DESMODUR
ETHACURE DESMOPHEN 1145 DESMOPHEN 1150 SOVERMOL 805 SOVERMOL 815 N3400
100
J 20 80 - - - 105
K 30 70 - - - 120
L 20 - 80 - - 90
M 30 - 70 - - 105
N 20 - - 80 - 90
P 30 - - 70 - 105
Q 20 - - - 80 95
R 30 - - - 70 110
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Table 5:
TENSILE ELONGATION FLEXURAL
SYSTEM FILM SET TIME STRENGTH AT BREAK STRENGTH
at 3mm (MINS) (Mpa) (%) (Mpa)
J 3.5 18.0 30 31.0
K 3 20.0 20 33.0
L 3.5 19.0 40 29.0
M 3 20.0 30 31.0
N 3.5 24.0 50 35.0
p 3 26.0 40 38.0
Q 3.5 25.0 40 32.0
R 3 26.0 30 34.0
Table 6:
SYSTEM BS 6920 T.O.C
FLAVOUR & ODOUR (mg/Litre)
J FAIL 2.5
K FAIL 2.2
L PASS 1.5
M PASS 1.2
N PASS 0.7
p PASS 0.6
Q FAIL 1.9
R FAIL 1.6
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Table 7:
COMPOSITION (pbw)
SYSTEM
DESMODUR N3800 DESMODUR N3400 ETHACURE 100
S 100 0 25
T 90 10 27
V 80 20 30
W 70 30 32.5
Table 8:
SYSTEM FILM SET TENSILE ELONGATION FLEXURAL
TIME @ 3mm STRENGTH AT BREAK (%) STRENGTH
(Mins) (MPa) (Mpa)
S 2.5 23.0 60 35.0
T 2.5 25.0 40 40.0
V 2 28.0 30 45.0
W 2 32.0 20 48.0
Table 9:
SYSTEM BS 6920 T.O.C GCMS GENERAL
FLAVOUR & ODOUR (mg/L) SURVEY
S PASS 0.5 Acceptable. No unknown
compounds present> 2 g/L
T PASS 0.5 Acceptable. No unknown
compounds present> 2 g/L
V PASS 0.4 Acceptable. No unknown
compounds present > 2 g/L
W PASS 0.4 Acceptable. No unknown
compounds present > 2 g/L
