Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PF 70080
CA 02785436 2012-06-21
Rigid foam envelopment of the connections of pipes
Description
The invention relates to the connections of at least two pipes or parts
thereof having a
connection region of the pipes adjoining the connection, wherein the
connection region
is enveloped by an open-celled rigid foam, preferably a rigid polyurethane
foam having
polyisocyanurate structures, and also the corresponding method of enveloping
the
pipes with foam and the pipe systems produced thereby.
Pipes sheathed with rigid polyurethane foams are known in the prior art and
are
described, for example, in EP-A-865 893 and DE-A-197 42012. Apart from these
insulated pipes, pipes which are not insulated but, for example, are enveloped
by a
compact exterior jacket, for example a jacket based on mineral and/or organic
material,
are also used, for example, for the transport of gas below the surface of
water. In
general, such a pipe comprises a plurality of layers. The outermost layer is
generally
concrete for protection and to increase the weight so that the pipes do not
float.
Underneath this, there is a further layer comprising, for example,
polypropylene,
polyethylene, epoxy resin, polyurethane coating or bitumen as corrosion
protection. At
the connections of such uninsulated pipes, the pipe can be protected by a
rigid
polyurethane foam which may, if appropriate, be surrounded by at least one
further
layer. Such a connection region is also referred to as sleeve.
The production of these sleeves, i.e., inter alia, the production of the rigid
polyurethane
foam, is, like the connection of the pipes for media, usually carried out on
board a pipe-
laying ship immediately before the laying of the pipes. Owing to the high
operating and
rental costs of the pipe-laying ships, there is an ongoing need for a high
degree of
rationalization in the production and laying of the pipes. At the same time,
the
connections (sleeves) have to be of such a nature that they protect the
interior pipe
against destruction in the case of point stress, for example an impact with an
anchor or
a trawl net. A corresponding stress test is the impact test in accordance with
DNV-RP-F111 ("Interface Between Trawl Gear And Pipelines").
It was therefore an object of the invention to configure connections of pipes
or parts
thereof in such a way that they can be produced more simply and more quickly,
the
mechanical requirements which the pipes have to meet in accordance with the
abovementioned impact test (DNV-RP-F111) are fulfilled and, in addition, the
connections have a low buoyancy.
A further object of the invention was to avoid the liquid modifiers as
described, for
example, in US 5489405, which are hazardous to health and often also toxic,
CA 02785436 2017-02-10
2
carcinogenic or mutagenic. The liquid modifiers are often mixtures of low-
boiling mineral
oil fractions (e.g. Enerdex 81 from BP) or phthalates (e.g. bis(2-ethylhexyl)
phthalate).
Furthermore, it was an object to improve the processability of the systems
used for
polyurethane production. Systems comprising a liquid modifier form two phases
after a
very short time, frequently in less than 30 minutes. Systems without these are
stable for
up to three days. This offers advantages in transport and in processing.
According to an aspect, the invention relates to a connection of at least two
pipes or
parts thereof having a connection region of the pipes adjoining the
connection, wherein
the connection region is enveloped by an open-celled rigid foam, wherein the
rigid foam
is a polyurethane foam having isocyanurate structures.
According to another aspect, the invention relates to a method of enveloping a
pipe
connection comprising at least two pipes or parts thereof connected to one
another with
foam, wherein an outer sheath is placed in the connection region adjoining the
connection point of the pipes in such a way that a hollow space arises in the
connection
region between the outer sheath and the connected pipes or pipe sections and
an open-
celled rigid foam is then produced in this hollow space, and the rigid foam is
a
polyurethane foam having isocyanurate structures.
According to the invention, this object is achieved by enveloping the
connection of at
least two pipes or parts thereof, preferably entire pipes, which have a
connection region
adjoining the connection in this connection region with open-celled rigid foam
which is
preferably a polyurethane foam having polyisocyanurate structures. The
associated
method of production and the use of open-celled rigid foam for enveloping
pipes, in
particular the point of connection between two pipes, are likewise provided by
the
invention.
Figure 1: this figure shows the longitudinal section through the axis of two
pipes (1)
which are surrounded by an anticorrosion layer (2) and a jacket (3) and are
connected
to one another (connection (8)). In the connection region (9) of the pipes in
the vicinity
of the connection (8), a second anticorrosion layer (5) is applied and the
space between
this anticorrosion layer and the sheath (4) is filled with open-celled rigid
foam (10). The
sheath (4) has a filling hole (6) and a venting hole (7).
CA 02785436 2017-02-10
2a
Figure 2 also shows the longitudinal section through the axis of two pipes (1)
which are
surrounded by an anticorrosion layer (2) and a jacket (3) and are connected to
one
another (connection (8)). In the connection region (9) in the vicinity of the
connection
(8), a second anticorrosion layer (5) which at least partly covers the
anticorrosion layer
(2) in the connection region (9) is applied. The space between the
anticorrosion layer
(5), if appropriate also (2), and the sheath (4) is filled with open-celled
rigid foam (10).
The sheath (4) has a filling hole (6) and a venting hole (7).
The pipes (1) can have any cross-sectional profile. In a preferred embodiment,
the pipes
(1) are uninsulated pipes. In a more preferred embodiment, the pipe is a tube,
i.e. the
pipe has a concentric structure about its axis. The tube then preferably has
an external
diameter of from 6 inches to 52 inches, preferably from 10 inches to 48 inches
and
particularly preferably from 16 inches to 42 inches, where one inch
corresponds to
2.54 cm.
The at least two pipes (1) are preferably made of steel. The pipes (1) are, in
a preferred
embodiment, surrounded by an anticorrosion coating (2) comprising one or more
layers.
In a further preferred embodiment, the single-layer or multilayer
anticorrosion coating
(2) has a thickness of from 0.1 cm to 2.0 cm, preferably from 0.2 cm to 1.5 cm
and
particularly preferably from 0.3 cm to 1.0 cm.
= PF 70080 CA 02785436 2012-06-21
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The anticorrosion coating (2) and/or (5) is preferably composed of bitumen,
polyethylene, polypropylene, polyurethane or epoxy resin. In a further
preferred
embodiment, an anticorrosion coating is also present on the inside of the
pipes (1).
For the purposes of the present text, the expression "uninsulated pipe" means
that the
pipes are, with the exception of the connections according to the invention,
not
enveloped by a foam, in particular not by an open-celled rigid foam. Thus, the
uninsulated pipes are pipes which are preferably not provided with thermal
insulation in
the form of a closed-celled rigid foam. Parts of pipes which are connected to
corresponding other parts of pipes are likewise comprised by the invention.
However,
in a preferred embodiment, the invention relates to at least two connected
pipes.
The pipes (1) are preferably used for the transport of media such as gas,
liquids and/or
bulk material, preferably for gas, and they are preferably round. For this
reason, the
expression "pipes for media" will also be used in the context of the present
invention.
For the definition of the connection between two pipes, reference is made to
DIN EN 489 insofar as this is applicable to the present pipes. The "connection
point" is
the point at which the two pipes are joined to one another; the connection
point is
preferably a weld between two pipes.
According to the invention, the pipe for media is enveloped in the region of
the
connection point (8) between two pipes (1) by the open-celled rigid foam which
is
preferably a rigid polyurethane foam comprising polyisocyanurate structures.
The
connection is preferably produced by welding together at least two pipes at
their ends.
As a result, the anticorrosion layer is at least partly absent in this
connection region (9).
In a preferred embodiment, a second anticorrosion layer (5) is also applied in
this
connection region (9). This second anticorrosion layer preferably comprises
bitumen,
polyethylene, polypropylene, polyurethane coating or epoxy resin. In one
embodiment,
this second anticorrosion layer (5) is composed of the same material as the
anticorrosion layer which surrounds the pipes (1) in the remaining region. In
another
embodiment, the anticorrosion layer (2) and the anticorrosion layer (5) are
composed
of different materials. In some embodiments, the two anticorrosion layers at
least partly
overlap.
The connection (8) and the connection region (9) are enveloped by the open-
celled
rigid foam, preferably polyurethane foam comprising isocyanurate structures.
Each
pipe (1) is preferably enveloped in the connection region (9) to a distance of
from 5 cm
to 60 cm, in each case measured from the connection point, by this open-celled
rigid
foam which is preferably rigid polyurethane foam comprising isocyanurate
structures.
= PF 70080
CA 02785436 2012-06-21
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As coated pipes (1), preference is given to using ones which are, preferably
with the
exception of their ends, enveloped by a compact material, preferably a
material based
on mineral and/or organic material, particularly preferably mineral material.
The region
at the ends of the pipes at which no compact sheathing material is present is,
after
joining of the ends, preferably welding together of the ends, and preferably
the
application of a suitable anticorrosion coating, enveloped by the open-celled
rigid foam,
preferably rigid polyurethane foam comprising isocyanurate structures.
A preferred compact mineral material is steel-reinforced concrete. A preferred
compact
organic material is epoxy resin or polyethylene foam. Particular preference is
thus
given to pipes in which an anticorrosion coating based on bitumen, epoxy
resin,
polyurethane, polyethylene and/or polypropylene is present between mineral
sheath
and interior steel pipe.
The open-celled rigid foam, preferably rigid polyurethane foam comprising
isocyanurate
structures, is preferably present between the pipe for media and an outer
sheath (4)
based on polyethylene or polypropylene or sheet metal. This outer sheath (4)
preferably has a thickness of from 0.1 cm to 1 cm. This means that, as
indicated later,
the open-celled rigid foam is preferably produced in a hollow space between
pipe (1)
and outer sheath (4), which is bounded laterally by the compact material.
The outer contour of the open-celled rigid foam in the connection region (9)
corresponds, in a preferred embodiment, to the outer contour of the connected
pipes in
this region; in a preferred embodiment in which the region is the connection
between
the two pipes, the external diameter in the connection region (9) is in the
range from 8
inches to 64 inches. Here, the external diameter is the diameter between the
outer
surfaces of the rigid polyurethane foam or, if this is covered by the sheath
(4), between
the outer surfaces of the sheath.
At least one filling hole (6) serves for filling of the hollow space between
connected
pipes, if appropriate with anticorrosion layer (5), and, if appropriate, the
lateral
jacket (4).
At least one second hole serves for venting (venting hole (7)). The
introduction of the
system from which the open-celled rigid foam is formed is preferably carried
out under
high pressure using a polyurethane machine. Pressures of from 80 bar to 180
bar,
more preferably from 100 bar to 160 bar and particularly preferably from 100
bar to
140 bar are employed for filling.
The open-celled rigid foam which surrounds the connection between two pipes,
if
appropriate with the surrounding sheath, is also referred to as sleeve.
PF 70080 CA 02785436 2012-06-21
As indicated above, the pipes (1) are preferably gas pipes which are
preferably laid
below the surface of water and are more preferably not insulated, i.e. which
with the
exception of the region of the sheath (4) are not enveloped by a closed-celled
rigid
foam, preferably a polyurethane foam.
5
Particular preference is given to connections which have two steel pipes for
media
whose ends are welded to one another and in the case of which open-celled
rigid foam,
preferably rigid polyurethane foam comprising isocyanurate structures, is
present
between the pipes (1) coated with an anticorrosion layer and a jacket and a
sheath (4).
The connection according to the invention is preferably present in pipelines,
preferably
having lengths of at least 0.5 km, particularly preferably in gas pipes, in
particular in
gas pipes which are present under water.
The open-celled rigid foam, preferably rigid polyurethane foam comprising
isocyanurate
structures, is preferably produced by reacting an isocyanate component (a)
with a
polyol mixture (b). The polyol mixture (b) preferably comprises (b1) polyols,
(b2)
catalysts and, if appropriate, (b3) chemical and/or physical blowing agents,
(b4)
crosslinkers, (b5) chain extenders, (b6) cell regulators and/or (b7)
additives. The
mixture of these listed constituents is also referred to as polyurethane
system.
As indicated above, the at least two pipes are, outside the connection region
(9) in
which they are enveloped by the open-celled rigid foam, preferably rigid
polyurethane
foam comprising isocyanurate structures, preferably surrounded by a compact
mineral
and/or organic material (jacket 3). Preference is given to methods in which a
sheath (4)
is placed over the jacket (3) in the connection region (9) between at least
two pipes (1)
which are surrounded by a jacket (3) so that a hollow space is formed between
connected pipes and sheath (4). Gaps arising between the jacket and the sheath
are
preferably sealed. In the sheath (4), there is at least one opening through
which the
polyurethane system is introduced. In one embodiment, this opening is so large
that
the displaced air can escape at the same time as the polyurethane system is
introduced. In other embodiments, the sheath (4) has at least one further
opening
(venting hole (7)) through which the air can escape during the filling
procedure.
Reaction of the polyurethane system forms an open-celled rigid polyurethane
foam,
preferably a rigid polyurethane foam comprising isocyanurate structures. In a
preferred
embodiment, the sheath (4) also remains at the connection after curing of the
open-
celled rigid foam. In another embodiment, the sheath (4) is removed again and
is more
preferably reusable. Here, preference is given to using a polyethylene film, a
polypropylene film or a metal sheet as sheath (4), with the opening for
venting
preferably being arranged at the highest point. Preference is given to fixing
films or
metal sheet on the compact mineral material by means of clamping straps.
PF 70080
CA 02785436 2012-06-21
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The above-described hollow space between pipes and shell is filled with the
isocyanate
component (a) and the polyol mixture (b) and, if appropriate, further
components,
preferably by means of a polyurethane metering machine which operates under
high or
low pressure.
These starting materials for the polyurethane system are described below:
Isocyanate components (a) used are the customary aliphatic, cycloaliphatic and
in
particular aromatic diisocyanates and/or polyisocyanates. Particular
preference is given
to mixtures of diphenylmethane diisocyanate and polyphenylene-polymethylene
polyisocyanates (crude MDI), in another preferred embodiment diphenylmethane
diisocyanate (MDI). The isocyanates can also have been modified, for example
by
incorporation of uretdione, carbamate, isocyanurate, carbodiimide, allophanate
and in
particular urethane groups. The isocyanate component (a) can also be used in
the form
of polyisocyanate prepolymers. These prepolymers are known in the prior art.
They are
prepared in a manner known per se by reacting the above-described
polyisocyanates
(a), for example at temperatures of about 80 C, with compounds having hydrogen
atoms which are reactive toward isocyanates, preferably polyols, to form
polyisocyanate prepolymers. The polyol:polyisocyanate ratio is generally
selected so
that the NCO content of the prepolymer is from 8 to 25% by weight, preferably
from 10
to 22% by weight, particularly preferably from 13 to 20% by weight. In
particular, crude
MDI is used for the production of rigid polyurethane foams. In a preferred
embodiment,
the isocyanate component (a) is selected so that it has a viscosity of less
than
600 mPas, preferably from 100 to 600 mPas, particularly preferably from 120 to
400mPas, in particular from 180 to 320 mPas, measured in accordance with
DIN 53019 at 25 C.
As compound which is reactive toward polyisocyanates (constituent or component
b), it
is possible to use polyols which are generally known for this purpose.
Possibilities are,
for example, compounds having at least two groups which are reactive toward
isocyanate, i.e. at least two hydrogen atoms which are reactive toward
isocyanate
groups. Examples are compounds having OH groups, SH groups, NH groups and/or
NH2 groups. Preferred compounds which are reactive toward isocyanates are
polyols
(constituent b1 or component b1). As polyols (b1), preference is given to
using
compounds based on polyesterols and/or polyetherols. The functionality of the
polyetherols and/or polyesterols is generally from 1.9 to 8, preferably from
2.2 to 6,
particularly preferably from 2.3 to 5. The polyols (b1) have a hydroxyl number
of
greater than 70 mg KOH/g, preferably greater than 100 mg KOH/g, particularly
preferably greater than 150 mg KOH/g, very particularly preferably 200 mg
KOH/g. It
has been found to be useful for the upper limit to the hydroxyl number to be
generally
600 mg KOH/g, preferably 500 mg KOH/g, in particular 400 mg KOH/g, very
particularly preferably 350 mg KOH/g. The abovementioned OH numbers are based
on
PF 70080 CA 02785436 2012-06-21
7
the totality of polyols (b1), which does not rule out the possibility of
individual
constituents of the mixture having higher or lower values.
It has surprisingly been found that, according to the invention, an index
which is very
low for PIR systems suffices to achieve the aims in the objects formulated at
the outset.
Contrary to general experience that PIR systems have poor flow properties, the
flowability (mold-filling capability) of the foam according to the invention
is sufficient for
filling even large pipe diameters, e.g. the diameters preferred according to
the
invention.
Furthermore, it is surprisingly possible to set the OHN to such a low value
that the
volumetric mixing ratio, i.e. the ratio of the polyol component to the
isocyanate
component, is about 1:1 and the PIR reaction nevertheless proceeds, with small
amounts of PIR catalyst, to a sufficient extent to make the desired strength
gains.
This is very advantageous since existing processing machines can, without an
additional outlay, process the foam which is preferred according to the
invention and
the amounts of the individual components to be processed are approximately the
same, which is of great importance for logistic reasons in the case of
offshore projects.
The component (b1) preferably comprises polyether polyols which are prepared
by
known processes, for example from one or more alkylene oxides having from 2 to
4
carbon atoms in the alkylene radical by anionic polymerization using alkali
metal
hydroxides such as sodium or potassium hydroxide or alkali metal alkoxides
such as
sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide as
catalysts with addition of at least one starter molecule comprising from 2 to
8,
preferably from 3 to 8, reactive hydrogen atoms in bound form or by cationic
polymerization using Lewis acids such as antimony pentachloride, boron
fluoride
etherate, etc., or bleaching earth as catalysts. Suitable alkylene oxides are,
for
example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide,
styrene
oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene
oxides can
be used individually, alternately in succession or as mixtures. Possible
starter
molecules are alcohols such as glycerol, trimethylolpropane (TMP),
pentaerythritol,
sucrose, sorbitol and also amines, such as methylamine, ethylamine,
isopropylamine,
butylamine, benzylamine, aniline, toluidine, toluenediamine (TDA),
naphthylamine,
ethylenediamine, diethylenetriamine, 4,4"-methylenedianiline, 1,3-
propanediamine, 1,6-
hexanediamine, ethanolamine, diethanolamine, triethanolamine and the like. It
is also
possible to use condensation products of formaldehyde, phenol and
diethanolamine or
ethanolamine, formaldehyde, alkylphenols and diethanolamine or ethanolamine,
formaldehyde, bisphenol A and diethanolamine or ethanolamine, formaldehyde,
aniline
and diethanolamine or ethanolamine, formaldehyde, cresol and diethanolamine or
ethanolamine, formaldehyde, toluidine and diethanolamine or ethanolamine and
also
PF 70080
CA 02785436 2012-06-21
8
formaldehyde, toluenediamine (TDA) and diethanolamine or ethanolamine and the
like
as starter molecules. Preference is given to using diethylene glycol,
propylene glycol,
pentaerythritol and glycerol as starter molecule.
In one embodiment, the polyol component (b1) comprises only one polyol, and in
a
preferred embodiment the component (b1) comprises a mixture of a plurality of
polyols.
For the purposes of the present invention, catalysts (b2) are firstly
catalysts which
accelerate the reaction of the isocyanates with the polyols (b2a) and also
ones which
promote the trimerization of isocyanates, i.e. the formation of
polyisocyanurate (PIR),
(b2b), which are also referred to as trimerization catalysts. The catalysts
b2a and b2b
are each used individually in a preferred embodiment and are used together in
another
preferred embodiment.
At least one trimerization catalyst (b2a) is preferably added to the polyol.
As PIR catalyst (b2b), preference is given to using alkali metal and/or
alkaline earth
metal compounds, preferably alkali metal salts such as potassium acetate,
potassium
octoate and potassium formate. Further preferred alkali metal compounds are,
inter
alia, alkali metal hydroxides such as sodium hydroxide and alkali metal
alkoxides such
as sodium methoxide and potassium isopropoxide and also alkali metal salts of
long-
chain fatty acids having from 10 to 20 carbon atoms and if appropriate lateral
OH
groups. Particular preference is given to potassium acetate as alkali metal
compound.
In an alternative preferred embodiment, PIR catalysts such as
tris(dialkylaminoalkyl)-s-
hexahydrotriazines, in particular tris(N,N-dimethylaminopropyI)-s-
hexahydrotriazine,
tetraalkylammonium hydroxides such as tetramethylammonium hydroxide are used
as
trimerization catalysts (b2b).
In a further preferred embodiment, the alkali metal and/or alkaline earth
metal
compounds, preferably alkali metal compounds, and PIR catalysts such as
tris(dialkylaminoalkyl)-s-hexahydrotriazines, in particular tris(N,N-
dimethylaminopropy1)-
s-hexahydrotriazine, tetraalkylammonium hydroxides, preferably
tetramethylammonium
hydroxide, are used together.
Catalysts (b2a) used for producing the rigid foams are, in particular,
compounds which
strongly accelerate the reaction of the reactive hydrogen atoms, in particular
of
hydroxyl-comprising compounds, of the component (b1) and, if appropriate, (b4)
and/or
(b5) with the organic modified or unmodified polyisocyanates (a).
In a preferred embodiment, basic amine compounds, preferably tertiary amines
such
as dimethylbenzylamine and/or dimethylcyclohexylamine, are used as catalysts
(b2a).
PF 70080 CA 02785436 2012-06-21
9
As amine catalysts, preference is given to using strongly basic amines.
Preferred
amines are amidines such as 2,3-dimethy1-3,4,5,6-tetrahydropyrimidine,
tertiary amines
such as triethylamine, tributylamine, dimethylbenzylamine, N-methylmorpholine,
N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-
tetramethylethylenediamine,
N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethylhexane-1,6-diamine,
N,N,N',N'-tetramethy1-2,2'-oxybis(ethylamine), methylbis(2-
dimethylaminoethyl)amine,
bis(dimethyldiethylaminoethyl) ether, pentamethyldiethylenetriamine,
tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea,
dimethylpiperazine,
1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane and aminoalkanol compounds
such
as triethanolamine, triisopropanolamine, N-methyldiethanolamine and
N-ethyldiethanolamine and dimethylethanolamine, which serve as gelling and/or
blowing catalysts and promote the gelling reaction and also the reaction of
the
isocyanate with water. Other preferred gelling catalysts are
diazobicycloundecane,
1,4-diazabicyclo[2.2.2]octane (Dabco), 1-methylimidazole and more preferably
dimethylcyclohexylamine.
The catalysts (b2b) are generally used in an amount of from 0.001% by weight
to 2%
by weight, preferably from 0.01% by weight to 1% by weight, particularly
preferably
from 0.01% by weight to 0.5% by weight, very particularly preferably from
0.01% by
weight to 0.3% by weight, of catalyst, based on the weight of the polyol
mixture (b) (but
without physical blowing agents).
It has surprisingly been found that even the abovementioned, very small
amounts of
PIR catalyst are sufficient to achieve the aims formulated in the objects.
It has likewise surprisingly been found that the PIR reaction does not have an
adverse
effect on the proportion of open cells in the foam.
The component (b) comprises chemical and/or physical blowing agents as
constituent
(b3). Preference is given to using chemical blowing agents. Water or
carboxylic acids,
preferably formic acid, are preferred. A particularly preferred chemical
blowing agent is
water. The chemical blowing agent is generally used in an amount of from 0.1
to 3% by
weight, in particular from 0.2 to 2.0% by weight, particularly preferably from
0.3 to 1.5%
by weight, based in the weight of the component (b), preferably polyol mixture
(b) (but
without physical blowing agents).
As mentioned above, the polyol mixture comprises, in another embodiment,
physical
blowing agent. Physical blowing agents are compounds which are dissolved or
emulsified in the starting materials for polyurethane production and vaporize
under the
conditions of polyurethane formation. These are preferably hydrocarbons,
halogenated
hydrocarbons and perfluorinated alkanes, e.g. perfluorohexane,
chlorofluorocarbons,
and also ethers, esters, ketones and/or acetals. These are preferably used in
an
amount of from 0.01% by weight to 20% by weight, more preferably from 0.1% by
= I I ,/%inNIMO
CA 02785436 2012-06-21
weight to 15% by weight, particularly preferably from 0.5 to 10% by weight,
based on
the total weight of the components b). Particular preference is given to using
fluorinated
hydrocarbons as blowing agents.
5 In a preferred embodiment, the polyol mixture (b) comprises cell
regulators as
constituent (b6). For the purposes of the present invention, cell regulators
are
compounds which during the foaming process influence the cell development,
cell
stabilization and also the subsequent cell opening. An example is Ortegol 501
(from
Goldschmidt).
10 The cell regulators are generally used in an amount of from 0.01 to 8%
by weight,
preferably from 0.02 to 6% by weight, particularly preferably from 0.05 to 4%
by weight,
based on the total weight of the polyol mixture (b) (but without physical
blowing
agents). It is also possible to use a mixture of various cell regulators.
In a further preferred embodiment, the polyol mixture (b) comprises
crosslinkers as
constituent (b4). For the purposes of the present invention, crosslinkers are
compounds which have a molecular weight of from 60 g/mol to <400 g/mol and
have
at least 3 hydrogen atoms which are reactive toward isocyanates. An example is
glycerol. The crosslinkers are generally used in an amount of from 1% by
weight to
10% by weight, preferably from 2% by weight to 6% by weight, based on the
total
weight of the polyol mixture (b) (but without physical blowing agents).
In a further preferred embodiment, the polyol mixture (b) comprises chain
extenders as
constituent (b5) in order to increase the crosslinking density. For the
purposes of the
present invention, chain extenders are compounds which have a molecular weight
of
from 60 g/mol to < 400 g/mol and have 2 hydrogen atoms which are reactive
toward
isocyanates. Examples are butanediol, diethylene glycol, dipropylene glycol
and
ethylene glycol. The chain extenders are generally used in an amount of from
1% by
weight to 20% by weight, preferably from 2% by weight to 15% by weight, based
on the
total weight of the polyol mixture (b) (but without physical blowing agents).
The components (b4) and (b5) can be used individually or in combination in the
polyol
mixture.
To allow isocyanurate structures to form in the foam, the index is preferably
in the
range from 160 to 500, particularly preferably from 160 to 400, in particular
from 165 to
300, very particularly preferably from 170 to 250, most preferably from 180 to
250.
The overall foam density (total amount of foam divided by the hollow volume of
the
sleeve) in accordance with DIN EN ISO 845 of the polyurethane foam comprising
isocyanurate structures is preferably in the range from 60 kg/m3 to 500 kg/m3,
particularly preferably from 80 kg/m' to 400 kg/m', in particular from 90 to
300 kg/m',
very particularly preferably from 100 kg/m3 to 250 kg/m'. For the present
purposes, the
1-'1- UUtSU
CA 02785436 2012-06-21
= 11
overall foam density is the foam density distribution over the volume occupied
by the
open-celled rigid foam.
In a particularly preferred embodiment, the rigid polyurethane foam having
isocyanurate structures is the reaction product of a polyol component B and an
isocyanate component A. The polyol component comprises at least from 45 to 55
parts
by weight of polyol A, from 15 to 35 parts by weight of polyol B and from 10
to 30 parts
by weight of polyol C, from 1.5 to 4 parts by weight of cell regulator,
preferably
Ortegol 501 from Goldschmidt having the 2009 composition, from 0.2 to 0.8 part
by
weight of an amine catalyst, preferably N,N-dimethylcyclohexylamine, from 0.02
to 0.3
part by weight of a trimerization catalyst, preferably potassium acetate, and
from 0.2 to
1 part by weight of water, with all the parts by weight of the constituents
introduced into
this polyol component B adding up to 100. The polyols A, B and C are described
in
more detail in the example.
The isocyanate component A in this preferred embodiment comprises at least one
of
the abovementioned isocyanates, preferably polymeric MDI, which is preferably
added
in an amount of from 105 to 130, preferably from 110 to 125, particularly
preferably
from 114 to 118, parts by weight to the 100 parts by weight of the polyol
component B.
Although the systems known from the prior art were able to pass the impact
test
(specifically: DNV-RP-F111 ¨ rectangular hammer head), this was only at a
relatively
high overall density of the foam. In the particularly preferred embodiment
mentioned,
the foams according to the invention withstand an impact of 7 kJ in the impact
test at a
foam density of 120 kg/m3. The foams known from the prior art require 160
kg/m3. In
comparison, the foams according to the invention withstand 12 kJ at 160 kg/m3.
The
foams known from the prior art do not. All impact values apply to the test
carried out
without sheath.
If appropriate, additives (b6) can also be incorporated into the polyurethane
system
according to the invention. For the purposes of the present invention,
additives (b6) are
the customary auxiliaries and additives known in the prior art, but without
physical
blowing agents. Mention may be made by way of example of surface-active
substances, fillers, dyes, pigments, flame retardants, antistatics, hydrolysis
inhibitors
and/or fungistatic and bacteriostatic substances.
The invention further provides the method of enveloping a pipe connection (8)
comprising at least two pipes (1) or parts thereof connected to one another,
wherein an
outer sheath is placed in the connection region adjoining the connection point
of the
pipes in such a way that a hollow space arises in the connection region
between the
outer sheath and the connected pipes or pipe sections and an open-celled rigid
foam is
then produced in this hollow space. Preference is given to using the rigid
foams which
have been described above, in particular polyurethane foams having the
compositions
I I I 1,""A1
CA 02785436 2012-06-21
12
indicated there. More preferably, any anticorrosion coating (2) which is
absent in the
connection region is supplemented by the anticorrosion coating (5) before
enveloping
the pipe connection with foam.
In a preferred embodiment, the connected pipes are, at least in the region
adjoining the
connection region, surrounded by a jacket (3) and an outer sheath (4) is
fastened over
the connection region and the jacket so as to form a hollow space which is
bounded on
the inside by pipes (1) and their connection (8), laterally by the jacket (3)
of the pipes
and on the outside by the outer sheath (4) in the connection region (9).
A system which cures to form an open-celled rigid foam is introduced into this
hollow
space. This system is preferably a system for producing polyurethane foam
having
isocyanurate structures, which system preferably comprises at least one A
component
composed of polyisocyanate (a) and a B component comprising a compound (b)
which
is reactive toward polyisocyanate and is preferably produced by mixing the A
component and the B component immediately before filling of the hollow space.
The sheath (4) more preferably comprises at least one filling hole (6),
preferably on its
upper side, and at least one venting hole (7), likewise preferably on the
upper side,
through which the air displaced from the hollow space during filling of the
system and
formation of the open-celled rigid foam can escape.
In a further preferred embodiment, the outer sheath is of such a nature that
it can be
removed again after production of the open-celled rigid foam. The sheath is
more
preferably coated with a release agent or with a very thin film which prevents
adhesion
of the sheath to the rigid foam and thus aids removal of the sheath.
The invention further provides for the use of open-celled rigid foams,
preferably
polyurethane foams having isocyanurate structures, for the envelopment of
pipes, in
particular the envelopment of the connection point of at least two pipes.
These are
preferably pipes used for the transport of media, preferably gases or liquids,
more
preferably mineral oil or natural gas, particularly preferably gases, in
particular natural
gas.
In further preferred embodiments, the pipes are laid under a surface of water;
the pipes
are particularly preferably laid in waters in which fishing with trawl nets is
carried out.
The invention is illustrated below by means of an example which serves to
illustrate the
subject matter of the invention but does not restrict the invention in any
way.
r-r= vucou
CA 02785436 2012-06-21
13
Example
The component B comprising the compound (b) which is reactive toward
polyisocyanate is based on the following polyol mixture:
Viskosity Molecular
Polyol type OH number Functionality
[25 C] weight
Polyol A 403 mg KOH/g 3.9 2200 545
Polyol B 42 mg KOH/g 2.7 950 3550
Polyol C 104 mg KOH/g 2 155 1070
Polyol A is based on sucrose, pentaerythritol, diethylene glycol and propylene
oxide.
Polyol B is based on glycerol, propylene oxide and ethylene oxide. Polyol C is
based
on propylene glycol and propylene oxide.
Formulation
Material Proportion by weight
Polyol A 49.72
Polyol B 25
Pc:4d C 20
Cell regulators
4
(e.g. Ortegol 501 from Goldschmidt)
N,N-Dimethylcyclohexylamine (DMCHA) 0.5
Potassium acetate 0.08
Water 0.7
Lupranat M 20S (polymeric MDI) 116
Isocyanate index 160
The polyol component is firstly mixed with the polyols A, B and C, the cell
regulator,
DMCHA and potassium acetate and also water (component B). A polymeric MDI is
then added as component A to this component B, the batch is mixed well using a
commercial high-pressure unit and is introduced via the filling hole into a
hollow space
provided. This hollow space is formed on a welded pipe connection whose pipes
(diameter: 48 inches) are surrounded by a concrete jacket. As surrounding
sheath, use
is made of a metal sheet which is drawn tight by means of three clamping
straps at
each of the concrete ends of the pipes and additionally in the middle of the
metal sheet.
The metal sheet produces a connection region having a thickness of 90 mm and a
width of 60 cm. The foam rises in the hollow space of the sleeve and fills it
completely
within the fiber time of the foam. When foam begins to come out of the space,
the filling
hole and the venting hole are closed in order to avoid further outflow of the
foam from
the hollow space of the sleeve. An overall foam density of 162 kg/m3 is
obtained.
=./.."0,10
CA 02785436 2012-06-21
14
The sleeve was (without metal sheet) subjected to the impact test in
accordance with
DNV-RP-F111 using a rectangular hammer and withstood an impact of 12 kJ
without
damage to the anticorrosion coating on the steel pipe.
