Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02877942 2014-12-24
Producing foams having improved properties
Description
The present invention relates to a composition for producing a rigid
polyurethane foam
comprising at least one polyol having a molecular weight of not less than 1700
g/mol and at
least one blowing agent as component A, and at least one polyisocyanate as
component B,
wherein the at least one polyisocyanate B comprises from 11 to 39.5 wt% of a
polyisocyanate
prepolymer, based on a polyether polyol having an OH number of at least 100 mg
KOH/g, to a
rigid polyurethane foam obtainable by reacting this composition, to a process
for producing such
a rigid polyurethane foam, to the use of such a rigid polyurethane foam for
insulation, especially
for pipe insulation, to an insulated pipe comprising a rigid polyurethane foam
and also to a
process for producing an insulated pipe.
Compositions for producing a polyurethane foam and the foams are already known
from the
prior art.
WO 01/18087 Al discloses a polyol composition comprising a specific mixture of
various
polyols for producing semi-flexible rigid polyurethane foams. Useful
polyisocyanate components
for these polyurethane foams include the common general knowledge
polyisocyanates such as
2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and polymeric
4,4'-
diphenylmethane diisocyanate and also isomers and mixtures thereof.
EP 0 906 354 B2 discloses a process for producing rigid polyurethane foams by
reacting
polyisocyanates with isocyanate-reactive compounds. Useful isocyanate-reactive
components
include various polyols based on polyfunctional alcohols and/or amines. Useful
polyisocyanate
components likewise include the customary polyisocyanates such as
diphenylmethane
diisocyanates.
DE 698 03 793 T2 discloses polyol formulations for producing polyurethane
foams. The polyol
formulations as per this document comprise a specific mixture of two different
polyols which
differ inter alia in molecular weight. Useful polyisocyanate components for
reaction with this
polyol mixture to form rigid polyurethane foams include the known
polyisocyanates such as
2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and polymeric
4,4'-diphenylmethane diisocyanate and also isomers and mixtures thereof.
EP 0 320 134 Al discloses polyisocyanate compositions for producing
polyurethane foams. The
specific polyisocyanate composition comprises 3 to 27 wt% of a prepolymer of
diphenylmethane
diisocyanate and a compound comprising two or more isocyanate-reactive groups
having a
molecular weight below 1000 g/mol.
DE 101 08 443 Al discloses a pressure vessel containing reaction products for
producing an
elastic foam. The reaction product comprises at least an isocyanate and a
mixture of polyether
CA 02877942 2014-12-24
2
polyols. Useful isocyanate components are said to include customary
isocyanates such as 2,4-
tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and polymeric 4,4'-
diphenylmethane
diisocyanate and also isomers and mixtures thereof, and also reaction products
of at least one
isocyanate-reactive compound with at least one di- and/or polyisocyanate, so-
called
prepolymers. What is disclosed in the cited document is a flexible and not a
rigid polyurethane
foam.
DE 196 10 262 Al discloses a process for producing hydrocarbon-blown rigid
polyurethane
foams. A composition comprising polyols and polyisocyanates as well as blowing
agent is
reacted and foamed up. The polyol component comprises 60 to 100% of polyethers
and/or
polyesters having a molecular weight of 250 to 1500 g/mol and two or more
hydroxyl groups, as
well as iso- and/or n-pentane as blowing agent.
Prior art rigid polyurethane foams are in need of improvement in respect of
their flexibility. The
preferably continuous production of insulated pipes requires that the pipes
produced be wound
up on rolls for transportation. The rigid polyurethane foam used as insulation
has to be
sufficiently flexible not to break during winding.
The present invention therefore has for its object to provide a rigid
polyurethane foam having
particularly good insulating properties and a sufficiently high flexibility so
that the continuously
produced insulated pipes may be wound up continuously. The present invention
therefore has
the more particular object of providing a composition for producing such rigid
polyurethane
foams, the rigid polyurethane foams, a process for their production and also
for the use of rigid
polyurethane foams obtained for insulation purposes.
These objects are achieved according to the present invention by the
composition for producing
a rigid polyurethane foam at least comprising:
(A) at least one polyol having a molecular weight of not less than 1700
g/mol and at least one
blowing agent as component A, and
(B) at least one polyisocyanate as component B,
wherein the at least one polyisocyanate B comprises from 11 to 39.5 wt% of a
polyisocyanate
prepolymer based on at least a polyether polyol having an OH number of at
least 100.
In a further embodiment, the present invention relates to a composition for
producing a rigid
polyurethane foam at least comprising:
(A) at least one polyol having a molecular weight of not less than 1700
g/mol and at least one
blowing agent as component A, and
(B) at least one polyisocyanate as component B,
CA 02877942 2014-12-24
3
wherein the at least one polyisocyanate comprises from 40 to 100 wt% of a
polyisocyanate
prepoiymer.
The present invention relates to a composition for producing a rigid
polyurethane foam. The
term rigid polyurethane foam for the purposes of the present invention relates
to a foam which
comprises at least a polyurethane; it is more preferable for the rigid
polyurethane foam of the
present invention to consist of polyurethane.
The term "rigid foam" is well known to a person skilled in the art and
describes, in general,
foams having rigid, close-mesh, crosslinked polymeric structures. Rigid foams
are closed-cell
foams having discrete cells in the foam which are divided from each other by
the polymer
matrix. They are notable for good thermal insulation performance.
The rigid polyurethane foam of the present invention preferably has a
compressive stress at
10% relative deformation of not less than 50 kPa, more preferably not less
than 100 kPa, very
preferably not less than 150 kPa. Furthermore, the rigid polyurethane foam of
the present
invention preferably has a DIN ISO 4590 closed-cell content of at least 70%,
more preferably
greater than 85%. Further details concerning rigid polyurethane foams of the
present invention
appear in "Kunststoffhandbuch, vol. 7, Polyurethane", Carl Hanser Verlag, 3rd
edition 1993,
chapter 6. DIN 7726 can also be referenced for polyurethane foams.
The individual components of the composition according to the present
invention will now be
elucidated in detail:
Component A:
The present invention composition for producing a rigid polyurethane foam
comprises a
component A comprising at least one polyol having a molecular weight of not
less than
1700 g/mol and at least one blowing agent.
In general, any polyol suitable for producing a rigid polyurethane foam can be
used for the
purposes of the present invention. The present invention utilizes at least one
polyol having a
molecular weight of not less than 1700 g/mol, preferably not less than 2500
g/mol and more
preferably not less than 4000 g/mol, for example 4350 g/mol. An upper limit to
the molecular
weight of the at least one polyols is generally 8000 g/mol, preferably 7000
g/mol and more
preferably 6000 g/mol.
Useful polyols for the purposes of the present invention include in general
compounds having
two or more isocyanate-reactive groups, i.e., having two or more hydrogen
atoms that are
reactive with isocyanate groups. Examples thereof are compounds having OH
groups, SH
groups, NH groups and/or NH2 groups.
= CA 02877942 2014-12-24
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Preferred polyols for the purposes of the present invention are compounds
based on
polyesterols or polyetherols, preferably polyetherols. Polyetherol and/or
polyesterol functionality
is generally in the range from 1.5 to 8, preferably in the range from 1.7 to 7
and more preferably
in the range from 1.9 to 6.
The polyols have a hydroxyl number (OH number) of generally greater than 10 mg
KOH/g,
preferably greater than 15 mg KOH/g and more preferably greater than 20 mg
KOH/g. The
upper limit to the hydroxyl number is generally 1000 mg KOH/g, preferably 900
mg KOH/g,
particularly 700 mg KOH/g.
It is preferable for the purposes of the present invention for the at least
one polypi present in
component A to utilize a mixture of polyols, for example comprising two,
three, four or more
different polyols, for example polyetherols and/or polyesterols, preferably
polyetherols.
When, as is preferred for the purposes of the present invention, a polyol
mixture is used, the OH
numbers stated above are based on the polyol mixture in total, which does not
foreclose the
possibility that individual constituents making up the mixture have higher or
lower values. It is,
for example, preferable for the purposes of the present invention for there to
be at least one
polyol in the mixture that has a hydroxyl number of 10 to 80 mg KOH/g and
preferably of 15 to
60 mg KOH/g.
Component A preferably comprises polyether polyols obtained by known methods,
for example
by anionic polymerization of alkali metal hydroxides, such as sodium hydroxide
or potassium
hydroxide, or alkali metal alkoxides, such as sodium methoxide, sodium
ethoxide, potassium
ethoxide or potassium isopropoxide, as catalysts and by adding at least one
starter molecule
comprising from 2 to 8 and preferably from 3 to 8 reactive hydrogen atoms in
bonded form, or
by cationic polymerization with Lewis acids, such as antimony pentachloride,
boron fluoride
etherate inter alia or fuller's earth as catalysts from one or more alkylene
oxides having 2 to 4
carbon atoms in the alkylene moiety.
Useful alkylene oxides include for example tetrahydrofuran, 1,3-propylene
oxide, 1,2-butylene
oxide, 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1,2-
propylene oxide.
The alkylene oxides can be used singly, alternatingly in succession or as
mixtures.
Useful starter compounds for the polyols in the composition of the present
invention include
alcohols, sugar compounds, amines, condensation products of at least one
amine, at least one
aromatic compound and formaldehyde, and mixtures thereof.
The present invention therefore relates with preference to that composition of
the present
invention wherein component A comprises at least one polyol based on a
compound selected
from the group consisting of alcohols, sugar compounds, amines, condensation
products of at
least one amine, at least one aromatic compound and formaldehyde, and mixtures
thereof.
CA 02877942 2014-12-24
Useful starter molecules include alcohols, for example glycerol,
trimethylolpropane (TMP),
pentaerythritol, diethylene glycol, sugar compounds, for example sucrose,
sorbitol, and also
amines, for example methylamine, ethylamine, isopropylamine, butylarnine,
benzylamine,
aniline, toluidine, tolylenediamine (TDA), naphthyleneamine, ethylenediarnine
(EDA),
5 diethylenetriamine, 4,4'-methylenedianiline, 1,3-propanediamine, 1,6-
hexanediamine,
ethanolamine, diethanolamine, triethanolamine and the like.
Useful starter molecules further include condensation products of at least one
amine, of at least
one aromatic compound and formaldehyde, especially condensation products of
formaldehyde,
phenol and diethanolamine/ethanolamine; formaldehyde, alkylphenols and
diethanolaminetethanolamine; formaldehyde, bisphenol A and
diethanolamine/ethanolamine;
formaldehyde, aniline and diethanolamine/ethanolamine; formaldehyde, kresol
and
diethanolamine/ethanolamine, formaldehyde, toluidine and
diethanolamine/ethanolamine; and
formaldehyde, tolylenediamine (TDA) and diethanolamine/ethanolamine; and the
like.
Very particular preference is given to using starter molecules selected from
the group consisting
of glycerol, tolylenediamine (TDA), sucrose, pentaerythritol, diethylene
glycol,
trimethylolpropane (IMP), ethylenediamine, sorbitol and mixtures thereof.
It is particularly preferable for component A of the composition according to
the present
invention to comprise a mixture of two or more polyols, most preferably three
polyols, especially
polyetherols.
In a particularly preferred embodiment, component A of the composition
according to the
present invention comprises two different polyetherols al and a2.
It is accordingly particularly preferable for the present invention to relate
to that composition
according to the present invention wherein component A comprises a polyetherol
mixture
comprising at least one polyetherol al based on at least one trihydric
alcohol, especially
glycerol, at least one polyetherol a2 based on at least one amine, especially
tolylenediamine
(TDA). In a further particularly preferred embodiment, component A of the
composition
according to the present invention comprises three different polyetherols al,
a2 and a3.
Therefore, in a further particularly preferred embodiment, the present
invention relates to that
composition according to the present invention wherein component A comprises a
polyetherol
mixture comprising at least one polyetherol al based on at least one trihydric
alcohol, especially
glycerol, at least one polyetherol a2 based on at least one amine, especially
tolylenediamine
(TDA), and at least one polyetherol a3 based on at least one sugar compound,
especially based
on a mixture comprising sucrose, pentaerythritol and diethylene glycol.
The preferred polyetherol al is based on at least one trihydric alcohol,
especially glycerol.
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it is further preferable for polyetherol al to be alkoxylatect with at least
one alkylene oxide,
preferably propylene oxide and/or ethylene oxide, preferably with propylene
oxide and ethylene
oxide.
It is preferable for the purposes of the present invention for polyetherol al
to have a molecular
weight of not less than 1700 g/mol. The molecular weight of polyetherol al is
for example in the
range from 1700 to 8000 g/mol, preferably in the range from 2200 to 7000 g/mol
and more
preferably in the range from 3000 to 6000 g/mol, for example 4350 g/mol.
The hydroxyl number (OH number) of polyetherol al is for example in the range
from 10 to
80 mg KOH/g, preferably in the range from 15 to 60 mg KOH/g and more
preferably in the
range from 25 to 45 mg KOH/g.
The functionality of polyetherol al is for example in the range from 1.5 to 6,
preferably in the
range from 1.7 to 5 and more preferably in the range from 1.9 to 4.5.
The preferred polyether polyol al is obtainable by following methods known to
a person skilled
in the art and mentioned above.
The preferred polyetherol a2 is based on at least one amine, especially
tolylenediamine (TDA).
It is further preferable for the polyetherol a2 to be alkoxylated with at
least one alkylene oxide,
preferably propylene oxide and/or ethylene oxide, preferably propylene oxide
and ethylene
oxide.
The molecular weight of polyetherol a2 is for example in the range from 200 to
2000 g/mol,
preferably in the range from 250 to 1500 g/mol and more preferably in the
range from 300 to
1000 g/mol, for example 530 g/mol.
The hydroxyl number (OH number) of polyetherol a2 is for example in the range
from 100 to
600 mg KOH/g, preferably in the range from 120 to 500 mg KOH/g and more
preferably in the
range from 150 to 450 mg KOH/g.
The functionality of polyetherol a2 is for example in the range from 2.0 to
5.0, preferably in the
range from 2.5 to 4.5 and more preferably in the range from 3.0 to 4.2.
The preferred polyether polyol a2 is obtainable by following methods known to
a person skilled
in the art and mentioned above.
The preferred polyetherol a3 is preferably based on a mixture comprising
sucrose,
pentaerythritol, diethylene glycol.
= CA 02877942 2014-12-24
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It is further preferable for the polyetherol a3 to be alkoxylated with at
least one alkylene oxide,
preferably propylene oxide and/or ethylene oxide, preferably propylene oxide.
The molecular weight of polyetherol a3 is for example in the range from 200 to
2000 g/mol,
preferably in the range from 300 to 1500 g/mol and more preferably in the
range from 400 to
1000 g/mol, for example 545 g/mol.
The hydroxyl number (OH number) of polyetherol a3 is for example in the range
from 100 to
600 mg KOH/g, preferably in the range from 200 to 500 mg KOH/g and more
preferably in the
range from 300 to 450 mg KOH/g.
The functionality of polyetherol a3 is for example in the range from 2.0 to
6.0, preferably in the
range from 2.5 to 5.5 and more preferably in the range from 3.0 to 5.2.
The preferred polyether polyol a3 is obtainable by following methods known to
a person skilled
in the art and mentioned above.
The amount of polyether polyol al in the mixture of recited polyether polyols
al, a2 and a3, the
use of which is preferred according to the present invention, is for example
in the range from 30
to 60 wt%, preferably in the range from 35 to 50 wt% and more preferably in
the range from 38
to 45 wt%, all based on the mixture comprising al, a2 and a3.
The amount of polyether polyol a2 in the mixture of recited polyether polyols
al, a2 and a3, the
use of which is preferred according to the present invention, is for example
in the range from 10
to 40 wt%, preferably in the range from 20 to 40 wt% and more preferably in
the range from 25
to 35 wt%, all based on the mixture comprising al, a2 and a3.
The amount of polyether polyol a3 in the mixture of recited polyether polyols
al, a2 and a3, the
use of which is preferred according to the present invention, is for example
in the range from 10
to 40 wt%, preferably in the range from 20 to 40 wt% and more preferably in
the range from 22
to 35 wt%, all based on the mixture comprising al, a2 and a3.
The amounts of al, a2, a3 and any stabilizer and/or water add up to 100 wt%
according to the
present invention.
In a further preferred embodiment of the present invention, component A of the
composition
according to the present invention comprises at least one additive selected
from the group
consisting of chain extenders, stabilizers, water, catalysts, surface-active
substances, foam
stabilizers, cell regulators, fillers, dyes, pigments, flame retardants,
antistats, hydrolysis control
agents and/or fungistatically and bacteriostatically active substances and
mixtures thereof.
For the purposes of the present invention, any chemical entity known for a
person skilled in the
art and capable of fulfilling the abovementioned functions can in general be
used as additive.
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Stabilizers, the presence of which is optional for the purposes of the present
invention, further
the development of a regular cellular structure in the course of foam
formation.
Examples include silicone-containing foam stabilizers, such as siloxane-
oxyalkylene copolymers
and other organopolysiloxanes. Also alkoxylation products of fatty alcohols,
oxoprocess
alcohols, fatty amines, alkylphenols, dialkylphenols, alkylcresols,
alkylresorcinol, naphthol,
alkylnaphthol, naphthylamine, aniline, alkylaniline, toluidine, bisphenol A,
alkylated bisphenol A,
polyvinyl alcohol, and also alkoxylation products of condensation products
formed from
formaldehyde and alkylphenols; formaldehyde and dialkylphenols; formaldehyde
and
alkylkresols; formaldehyde and alkylresorcinol; formaldehyde and aniline;
formaldehyde and
toluidine; formaldehyde and naphthol; formaldehyde and alkylnaphthol; and
formaldehyde and
bisphenol A; or mixtures of two or more thereof.
The amount which is used of the at least one stabilizer is generally in the
range from 0.2 to
5 wt% and preferably in the range from 0.5 to 4.0 wt%, all based on the total
weight of at least
one polyol, stabilizer and optionally water.
Chain extenders, the presence of which is optional according to the present
invention, are
generally compounds having a molecular weight of 60 to 400 g/mol and 2
isocyanate-reactive
hydrogen atoms. Examples thereof are butanediol, diethylene glycol,
dipropylene glycol and
ethylene glycol.
Optionally present chain extenders are generally used in an amount of 0 to 20
wt%, preferably
of 2 to 15 wt%, based on the total weight of the at least one polyol and
optionally present
stabilizers and/or water.
Crosslinkers, the presence of which is optional according to the present
invention serve for
example to increase the crosslink density. Crosslinkers are generally
compounds having a
molecular weight of 60 to 400 g/rnol and more than 2, for example 3,
isocyanate-reactive
hydrogen atoms. Glycerol is an example.
Optionally present crosslinkers are generally used in an amount of 0 to 20 wt%
preferably of 2
to 15 wt%, based on the total weight of the at least one polyol and optionally
present stabilizers
and/or water. Optionally present flame retardants may be halogenated or
halogen-free flame
retardants. Preferred halogen-free flame retardants include for example
ammonium
polyphosphate, aluminum hydroxide, isocyanurate derivatives and carbonates of
alkaline earth
metals. Preference is given to using phosphates, for example triethyl
phosphate, phosphonates,
for example diethyl N,N-di(2-hydroxyethyl)aminomethylphosphonate, melamine,
melamine
derivatives such as, for example, melamine cyanurate and/or mixtures of
melamine and
expandable graphite. It will be appreciated that foams of the present
invention are also
obtainable when in addition to the preferably used halogen-free flame
retardants further,
halogenated flame retardants known in polyurethane chemistry are used/co-used,
for example
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trikresyl phosphate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl)
phosphate, tetrakis(2-
chloroethyl)ethylene diphosphate, dimethylmethane phosphonate, diethyl
diethanolaminomethylphosphonate and also commercially available halogenated
flame-
retardant polyols. In addition to the halogen-substituted phosphates already
mentioned, further
organic or inorganic flame retardants can also be used, such as red
phosphorus, aluminum
oxide hydrate, antimony trioxide, arsenic oxide, calcium sulfate, corn starch
and/or optionally
aromatic polyesters, to flameproof the polyisocyanate polyaddit ion products.
Halogenated flame retardants are generally the flame retardants known from the
prior art, for
example brominated ethers (Ixol), brominated alcohols such as dibromoneopentyl
alcohol,
tribromoneopentyl alcohol and PHT-4-diol and also chlorinated phosphates,
e.g., tris(2-
chloroethyl) phosphate, tris(2-chloroisopropyl) phosphate (TCPP), tris(1,3-
dichloroisopropyl)
phosphate, tris(2,3-dibromopropyl) phosphate and tetrakis(2-
chloroethyl)ethylene diphosphate.
Flame retardants are generally used in an amount of 0 wt% to 60 wt%,
preferably 0 wt% to
50 wt% and more preferably 0 wt% to 40 wt%, all based on the total weight of
the at least one
polyol and optionally present stabilizer and/or water.
In a preferred embodiment, component A comprises at least one catalyst.
Preference for use as catalysts in component A and to produce the foams is
given especially to
compounds that have a substantial speeding effect on the reaction of reactive
hydrogen atoms,
especially of hydroxyl-containing compounds of the at least one polyol with
the at least one
polyisocyanate.
Useful catalysts include for example organometallic compounds, preferably
organotin
compounds, such as tin(11) salts of organic carboxylic acids, e.g., tin(11)
acetate, tin(11) octoate,
tin(11) ethylhexanoate and tin(II) laurate, and the dialkyltin(IV) salts of
organic carboxylic acids,
e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and
dioctyltin diacetate. The
organometallic compounds can be used alone or combined with strong basic
amines. Examples
are amidines, such as 2,3-dimethy1-3,4,5,6-tetrahydropyrimidine, tertiary
amines which, like
triethylamine, tributylamine, dimethylbenzylamine, N-methylnnorpholine, N-
ethylmorpholine,
N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-
tetramethylbutanediamine, N,N,N',N.-tetrarnethylhexane-1,6-diamine,
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
serve as
blowing catalysts which in addition to the gel reaction favor especially the
reaction of the
isocyanate with water. Diazabicycloundecane, 1,4-diazabicyclo-[2.2.2}octane
(Dabco),
1-methylimidazole and preferably dimethylcyclohexylamine are used as gel
catalyst.
CA 02877942 2014-12-24
The present invention can also utilize common general knowledge catalysts to
augment the
polyisocyanurate reaction (i.e., PER catalysts), in which case a polyurethane
is formed according
to the present invention. Alkali and/or alkaline earth metal compounds,
especially alkali metal
salts, for example potassium acetate, potassium octanoate and potassium
formate are used for
5 example. The use of potassium acetate is preferred. Further alkali and/or
alkaline earth metal
compounds to be used according to the present invention include alkali metal
hydroxide, 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 10
to 20 carbon atoms
and optionally lateral OH groups. Other known PIR catalysts are also possible,
such as
10 tris(dialkylaminoalkyl)-s-hexahydrotriazines, especially tris(N,N-
dimethylaminopropyl)-s-
hexahydrotriazine, tetraalkylammonium hydroxides, such as tetramethylammonium
hydroxide.
It is particularly preferable to use dimethylcyclohexylamine as catalyst.
The optionally present at least one catalyst is generally used in an amount of
0.1 to 10 wt% and
preferably of 0.5 to 5 wt%, based on the total weight of the at least one
polyol and optionally
present stabilizer and/or water.
The composition of the present invention for producing a rigid polyurethane
foam also
comprises at least one blowing agent as component A in addition to the at
least one polyol
having a molecular weight of not less than 1700 g/mol.
Chemical and/or physical blowing agents may be present in the composition of
the present
invention.
Preferred chemical blowing agents are water or carboxylic acids, especially
formic acid.
Chemical blowing agents are generally used in an amount of 0.1 to 10 wt%,
especially of 0.5 to
7 wt%, based on the total weight of the at least one polyol and optionally
present stabilizer
and/or water.
It is preferable to use at least one physical blowing agent in the present
invention. Physical
blowing agents are compounds which are in a dissolved or emulsified state in
the composition
of the present invention and vaporize under the conditions of polyurethane
formation. They
include for example hydrocarbons, for example cyclopentane or a mixture
comprising
cyclopentane, halogenated hydrocarbons, and other compounds, for example
perfluorinated
alkanes, such as perfluorohexane, chlorofluorocarbons, and also ethers,
esters, ketones and/or
acetals. These are typically used in an amount of 1 to 30 wt%, preferably 2 to
25 wt% and more
preferably 3 to 20 wt%, based on the total weight of at least one polyol and
optionally present
stabilizer and/or water.
The present invention therefore relates with preference to that composition
according to the
present invention wherein the blowing agent is cyclopentane or a mixture
comprising
CA 02877942 2014-12-24
/1
cyclopentane. For example, a mixture of cyclopentane and water can be used as
blowing agent
in the present invention.
Component B:
The composition of the present invention comprises as component B at least one
polyisocyanate, wherein the at least one polyisocyanate B comprises from 11 to
39.5 wt% of a
polyisocyanate prepolymer based on at least one polyether polyol having an OH
number of at
least 100 mg KOH/g.
For the purposes of the present invention, the term "polyisocyanate" is to be
understood as
meaning a compound having two or more isocyanate groups. Useful organic
polyisocyanates
include for example aliphatic, cycloaliphatic and especially aromatic di- or
polyisocyanates.
Specific examples are aliphatic diisocyanates, such as 1,6-hexamethylene
diisocyanate,
2-methyl-1,5-pentamethylene diisocyanate, 2-ethyl-1,4-butylene diisocyanate or
mixtures of 2 or
more of said C6-alkylene diisocyanates, 1,5-pentamethylene diisocyanate and
1,4-butylene
diisocyanate, cycloaliphatic diisocyanates, such as 1-isocyanato-3,3,5-
trimethy1-5-
isocyanatomethylcyclohexane (isophorone diisocyanate), 1,4-cyclohexane
diisocyanate,
1-methyl-2,4- and -2,6-cyclohexane diisocyanate and also the corresponding
isomeric mixtures,
4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate and also the
corresponding isomeric
mixtures and preferably aromatic diisocyanates, such as 1,5-naphthylene
diisocyanate (1,5-
NU), 2,4- and 2,6-tolylene diisocyanate (TDI) and also mixtures thereof, 2,4'-
, 2,2'-, and
preferably 4,4'-diphenylmethane diisocyanate (nnMDI) and also mixtures of two
or more of these
isomers, polyphenyl polymethylene polyisocyanates (polymeric MDI, pMDI) having
two or more
aromatic systems, mixtures of 2,4'-, 2,2'- and 4,4'-diphenylmethane
diisocyanates and
polyphenyl polymethylene polyisocyanates (crude MDI), mixtures of crude MDI
and tolylene
diisocyanates, polyphenyl polyisocyanates, carbodiimide-modified liquid 4,4'-
and/or 2,4-
diphenylnnethane diisocyanates and 4,4'-diisocyanato-1,2-diphenylethane. It is
particularly
preferable to use isocyanates that are liquid at 25 C.
It is an essential aspect of the present invention that the polyisocyanate
component B
comprises 11 to 39.5 wt%, preferably 12 to 35 wt%, more preferably 12.5 to 33
wt% of a
polyisocyanate prepolymer, based on at least one polyether polyol having an OH
number of at
least 100 mg KOH/g.
In another embodiment, the polyisocyanate component B comprises 40 to 100 wt%,
preferably
to 100 wt%, more preferably 50 to 100 wt% and most preferably 100 wt% of a
polyisocyanate prepolymer.
40 Polyisocyanate prepolymers per se are known from the prior art. They are
prepared in a known
manner by reacting above-described polyisocyanates, for example at
temperatures of about
80 C, with compounds having isocyanate-reactive hydrogen atoms, preferably
with polyols, to
form polyisocyanate prepolymers. The polyol-polyisocyanate ratio is preferably
chosen such
CA 02877942 2014-12-24
12
that the NCO content of the prepolymer is in the range from 8 to 35%,
preferably in the range
from 15 to 30% and more preferably in the range from 20 to 30%.
Useful polyols for preparing the polyisocyanate prepolymers include in
principle the polyols
mentioned above in respect of component A, i.e., polyether polyols having an
OH number of at
least 100 mg KOH/g. The prepolymers which are used according to the present
invention are
prepared using, for example, polyether polyols based on glycerol as starter
compound
alkoxylated with ethylene oxide and/or propylene oxide. The polyisocyanate
prepolymers are
preferably prepared using dipropylene glycol and/or polypropylene glycol.
According to the present invention, component B utilizes polyether polyols
having an OH
number of at least 100 mg KOH/g. The hydroxyl number (OH number) of the
polyether polyols
is preferably for example in the range from 100 to 600 mg KOH/g or preferably
in the range from
150 to 500 mg KOH/g and even more preferably in the range from 200 to 450 mg
KOH/g.
The functionality of the polyetherol used in components B is for example in
the range from 1.5
to 6, preferably in the range from 1.7 to 5 and more preferably in the range
from 1.9 to 4.5.
In a further embodiment, the polyols used for preparing the polyisocyanate
prepolymers can in
principle be the polyols mentioned above in respect of components A, i.e.,
polyetherols and/or
polyesterols. The preferred prepolymers of the present invention are prepared
by reacting these
polyetherols with appropriate di- and/or polyisocyanates. Preferably 4,4'-
mMD1, pMDI or a
mixture thereof is reacted with an appropriate polyol, preferably with a
polypropylene glycol.
Polyisocyanate prepolymers preferably used according to the present invention
have a
functionality of for example 1.0 to 4.0, preferably 2.0 to 3Ø
In a further embodiment which is preferred according to the present invention,
component B
utilizes a mixture of at least one polyisocyanate prepolymer and at least one
polyisocyanate
having the aforementioned prepolymer content. Preferred mixtures comprise for
example pMDI
and/or mMDI, in addition to the polyisocyanate prepolymer.
In a very particularly preferred embodiment of the present invention,
component B comprises a
prepolymer of 4,4'-mMDI, dipropylene glycol and polypropylene glycol (OH
number 250 mg
KOH/g), having an NCO content of 22.9% and an average functionality of 2.05;
the prepolymer
content is 31%,
or
a prepolymer of 4,4'-mMDI, pMDI and polypropylene glycol (OH number 250 mg
KOH/g) having
an NCO content of 28.5% and an average functionality of 2.4; the prepolymer
content is 13%,
optionally
CA 02877942 2014-12-24
13
optionally in admixture with further polyisocyanates, such as
a mixture of 4,4'-diphenylmethane diisocyanate with higher-functional
oligomers and isomers,
having an NCO content of 31.5% and an average functionality of about 2.7
or
a carbodiimide-modified 4,4'-mMDI, having an NCO content of 29.5% and an
average
functionality of 2.2. The composition of the present invention generally
comprises components A
and B in such amounts that the isocyanate index is generally in the range from
50 to 175,
preferably in the range from 80 to 160, more preferably in the range from 100
to 150, for
example 120 1.
The present invention also relates to a rigid polyurethane foam obtainable by
reacting the
composition of the present invention.
The present invention also relates to a process for producing a rigid
polyurethane foam of the
present invention from a composition of the present invention, comprising at
least the steps of:
(1) contacting components A and B to obtain a reaction product, and
(2) foaming up the reaction product obtained in step (1).
Preferably in accordance with the invention, and in a manner known to the
skilled person, steps
(1) and (2) take place simultaneously ¨ that is, while components A and B are
reacting with one
another, the reaction product formed undergoes foaming. It is also possible
for foaming of the
reaction product to continue after the end of reaction as well.
The rigid foams of the present invention are advantageously produced by the
one-shot process,
for example using high-pressure or low-pressure technology. It will turn out
to be particularly
advantageous to use the two-component process to contact components A and B
(step 1).
Components A and B are typically mixed and reacted at a temperature of 15 to
80 C, preferably
of 20 to 60 C and especially of 20 to 35 C, optionally under elevated
pressure. Mixing can be
effected mechanically using a stirrer, using a stirred screw or by high-
pressure mixing in a
nozzle or mix head.
The foaming as per step (2) of the present invention is subsequently effected
by expanding the
incorporated blowing agent under the stated reaction conditions. Foaming can
be effected in
appropriate molds in order that the rigid polyurethane foam of the present
invention may be
obtained in corresponding geometric shapes.
= CA 02877942 2014-12-24
14
The density of rigid polyurethane foams of the present invention is preferably
in the range from
20 to 200 kg/m3, more preferably in the range from 30 to 100 kg/m3 and
especially in the range
from 35 to 80 kg/m3.
The rigid polyurethane foams of the present invention preferably have a
compressive strength
of greater than 0.10 N/mm' and a thermal conductivity of less than 27 mVV/m*K
at 23 C mean
temperature.
The rigid polyurethane foam of the present invention is preferably used in the
present invention
as insulation, preferably as pipe insulation.
The present invention therefore further relates to the use of a rigid
polyurethane foam of the
present invention for insulation, preferably for pipe insulation.
The present invention also relates to an insulated pipe comprising a rigid
polyurethane foam of
the present invention.
The production of insulated pipes is generally familiar to a person skilled in
the art. In an
example of a possible process, the composition of the present invention of
components A and B
is filled, preferably continuously, into a tubularly preshaped, optionally
multi-ply, preferably
diffusion-inhibiting film surrounding a media pipe with an annular gap to be
filled to produce the
rigid polyurethane foam, with the components A and B reacting together and the
reaction
product foaming up to form the rigid polyurethane foam, and the rigid
polyurethane foam
surrounded by the film is led, preferably continuously, into an extruder,
preferably into a ring
extruder, and a thermoplastic material is extruded onto the film. The
insulated pipe formed can
then be cooled, by being passed through a cooling water bath, for example.
The present invention therefore further provides a process for producing an
insulated pipe,
preferably the insulated pipe of the present invention, comprising at least
one rigid polyurethane
foam of the present invention, where the composition of the present invention
comprising
components A and B for producing the rigid polyurethane foam is filled,
preferably continuously,
into a tubularly preshaped, optionally multi-ply, preferably diffusion-
inhibiting film surrounding a
media pipe with an annular gap to be filled, with components A and B reacting
with one another
and with the reaction product foaming to form the rigid polyurethane foam, and
the rigid
polyurethane foam surrounded by the film is led, preferably continuously, into
an extruder,
preferably into a ring extruder, and a thermoplastic material is extruded onto
the film.
Since winding up the insulated pipes is easily possible owing to the high
flexibility of the rigid
polyurethane foam of the present invention, there is no need to join the pipes
which are
preferably produced continuously. It is thus possible to produce insulated
pipes having a length
of more than 50 m, preferably more than 200 m and especially more than 400 m.
= = CA 02877942 2014-12-24
The media pipe may be based for example on the following materials: metals,
especially
copper, stainless steel, unalloyed steel and aluminum and also plastics,
especially crosslinked
polyethylene (PEX). Media pipe wall thickness can typically be in the range
from 0.5 mm to
mm. Media pipe overall diameter is generally in the range from 25 to 1000 mm
and
5 preferably in the range from 25 to 400 mm. The rigid polyurethane foam
may adhere to the
media pipe. Alternatively, customary release agents can be applied to the
outer surface of the
media pipe to prevent adherence of the rigid polyurethane foam to the media
pipe.
The jacketing pipe may be based for example on the following materials:
thermoplastics,
10 especially HDPE and LDPE, and metals, for example wind-and-fold
sheeting.
After passing through the cooling water bath, the insulated pipe can be wound
up on drums
above 1 m, preferably above 1.5 m and most preferably above 2 m in diameter.
This creates
high tensile loads on the outside surface and high compressive loads on the
inside surface,
15 which the rigid polyurethane foam of the present invention is easily
able to bear. The rigid
polyurethane foam of the present invention has sufficient flexibility to
withstand the tensile load
and sufficient compressive strength to withstand the compressive load.
The jacketing pipe can consist of one or more layers, for example of the
optionally diffusion-
20 inhibiting, optionally multi-ply film described at the outset and a
further, preferably thicker layer
of preferably thermoplastic. The jacketing pipe overall wall thickness
including the film where
appropriate is generally in the range from 1 mm to 25 mm.
Examples:
Inventive rigid polyurethane foams 1, 2, 3 and 4 and comparative foams V5, V6,
V7 and V8 are
produced. The isocyanates and the isocyanate-reactive components were foamed
up together
with the blowing agents, catalysts and all further admixtures at an index of
120 1. For foaming,
a laboratory stirrer was used in a beaker at a rate of 1400 revolutions per
minute for 10
seconds. This beaker test is used to determine the reaction times and the free
rise density.
Further parameters are determined on foamed structures obtained by pouring the
reaction
mixture stirred in the beaker into a box mold measuring 200 x 200 x 70 mm3.
The formulations were all adjusted to a fiber time of 90 10 s and a free
rise density of
52 3 g/I.
Methods of measurement
Compressive strengths and moduli of elasticity in compression were measured on
the rigid
polyurethane foams to DIN 53421/DIN EN ISO 604.
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Thermal conductivity was determined after 24 hours' storage under standard
conditions. The
test specimens had the dimensions of 200 x 200 x 30 mm3. Thermal conductivity
is then
determined at a mean temperature of 23 C using a Hest A50 plate-type heat
flow meter.
Closed-cell content was determined using a gas displacement pyknometer in line
with
DIN EN ISO 4590.
The 3 point bending test was carried out in line with DIN 53423. The
deflection limit is 30 mm.
Flexural strength was calculated at peak force. Deflection at break is the
deflection in the middle
of the test specimen at the moment of breaking.
Formulations and test results are shown in Table 1. The table shows that using
a rigid PU foam
system of the present invention distinctly improves deflection at break and
hence foam
flexibility. This enhanced flexibility was achieved without sacrificing the
thermal conductivity and
compressive strength, the most important properties of a rigid polyurethane
foam system.
Table 1
Test
1 2 3 4 V5 V6 V7 V8
Cornponent A
Polyether al 40 40 40 40 40 48.5 40
40
Polyether a2 30 30 30 30 30 48.5 30
30
Polyether a3 27 27 27 27 27 27
27
Stabilizer 2 2 2 2 2 2 2
2
Water 1 1 1 1 1 1 1
1
Sum total 100 100 100 100 100 100
100 100
DMCHA 2.5 2 2 2 2 1.2 1.5
2
Cyclopentane 9 8.5 8.5 8 8.5 7.5 8
8
Component B, isocyanate index 120 1
lsocyanate 1 - 50 - 100 100
-
Isocyanate 2 50 67 -
100
Isocyanate 3 100 50 50 33
Isocyanate 4 - 100
Sum total 100 100 100 100 100 100
100 100
including prepolymer 31 15.5 15.5 13 10.3 0 0 0
Foam properties at core pipe densities 65 6 kg/m3
Compressive test
Compressive strength (N/rnm2) nd 0.235 0.223 0.251 0.266 0.227 0.243 0.224
Modulus of elasticity (N/rnm2) 5.40 7.23 6.67 8.45 9.02
6.58 7.22 7.03
3 point bending test
0.39 0.44 0.37 0.52 0.54 0.5.2 0.44 0.37
Flexural strength (N/mm2)
at deflection (mm)
21.5 21.0 , 21.8 17.1 16.4 18.4 15.4 15.9
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Deflection at break (mm) 26.3 24.3 27.0 23.0 18.0 I 18.0
15.3-T 17.0
Closed-cell content (Vo) 90 91 89 90 91 92 89
89
Thermal conductivity (m\f\f/m*K) 23.0 23.2 23.4 24.8 25.0
23.4 23.4 25.5
Unless stated otherwise, the values are given in wt%.
The following components were used:
Polyether al: started with glycerol, alkoxylated with PO/EO, OH number 35
mg KOH/g,
functionality 2.7, mean molecular weight 4350 g/mol
Polyether a2: started with TDA (tolylenediamine), alkoxylated with EO and
PO, OH number
390 mg KOH/g, functionality 3.8, mean molecular weight 530 g/mol
Polyether a3: started with sucrose, pentaerythritol and diethylene
glycol, alkoxylated with
PO, OH number 403 mg KOH/g, functionality 3.9, mean molecular weight
545 g/mol
Stabilizer: polysiloxane stabilizer (L 6900 from Momentive)
DMCHA: dimethylcyclohexylamine
Isocyanate 1: IsoPMDI 92140 from BASF SE, mixture of 4,4'-diphenylmethane
diisocyanate
with higher-functional oligomers and isomers, with NCO content of 31.5% and
mean functionality of about 2.7
Isocyanate 2: carbodiimide-modified 4,4'-mMDI, with NCO content of 29.5%
and a mean
functionality of 2.2
Isocyanate 3: quasi prepolymer of 4,4'-mMDI, dipropylene glycol and
polypropylene glycol
(OH number 250 mg KOH/g), with NCO content of 22.9% and a mean
functionality of 2.05; the prepolymer content is 31%.
Isocyanate 4: quasi prepolymer of 4,4'-mMDI, pMDI and polypropylene
glycol (OH number
250 mg KOH/g), with NCO content of 28.5% and a mean functionality of 2.4;
the prepolymer content is 13%.
