Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02797528 2012-10-17
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1
Process for producing rigid polyurethane foams
Description
.. The invention relates to a process for producing rigid polyurethane foams
by reacting
polyisocyanates with b) compounds having at least two hydrogen atoms which are
re-
active toward isocyanate groups.
Rigid polyurethane foams have been known for a long time and are used
predominant-
ly for heat and cold insulation, e.g. in refrigeration appliances, in hot
water storages, in
district heating pipes or in building and construction, for example in
sandwich elements.
A summary overview of the production and use of rigid polyurethane foams may
be
found, for example, in Kunststoff¨Handbuch, Volume 7, Polyurethane 1st edition
1966,
edited by Dr. R. Vieweg and Dr. A. Hochtlen, 2nd edition 1983, edited by Dr.
Gunter
Oertel, and 3rd edition 1993, edited by Dr. Gunter Oertel, Carl Hanser Verlag,
Munich,
Vienna.
They are usually produced by reacting polyisocyanates with compounds having at
least
two hydrogen atoms which are reactive toward isocyanate groups in the presence
of
catalysts, blowing agents and auxiliaries and/or additives.
Important requirements which rigid polyurethane foams have to meet are a low
thermal
conductivity, good flowability, satisfactory adhesion of the foam to the
covering layers
and good mechanical properties.
A further requirement which rigid polyurethane foams have to meet is good
burning
behavior. This is of great importance in, in particular, applications in the
building sector,
particularly in the case of composite elements comprising metallic covering
layers and
a core composed of polyurethane or polyisocyanurate foam. The term
polyisocyanurate
foam usually refers to a foam which comprises not only urethane groups but
also iso-
cyanurate groups. In the following, the term rigid polyurethane foam can also
encom-
pass polyisocyanurate foam.
Polyisocyanurate foams in particular frequently display unsatisfactory
adhesion to the
metallic covering layers. To remedy this deficiency, a bonding agent is
usually applied
between the covering layer and the foam, as described, for example, in WO
99/00559.
WO 2005090432 describes a process for producing rigid polyurethane foams
produced
using a mixture of a polyester alcohol based on an aromatic carboxylic acid
and at
least one polyether alcohol based on aromatic amines. The use of the polyester
alco-
hols is said to reduce the thermal conductivity of the foam and improve the
compatibil-
ity with the blowing agent. The foams produced by this process are preferably
used in
refrigeration appliances.
2
A further challenge which is always present in the use of rigid polyurethane
foams is
improving the flame resistance of the foams. Flame retardants are usually
added to the
foam for this purpose. The addition of the flame retardants can alter the
mechanical
properties and the processing properties of the foams. Furthermore, it is
desirable to
restrict the use of flame retardants, in particular those based on halogens,
especially
bromine, in the production of rigid polyurethane foams.
A further ongoing requirement is to improve the adhesion of the foams to the
covering
layers, in particular to reduce or completely avoid the use of bonding agents.
It was therefore an object of the invention to develop a process for producing
rigid pol-
yurethane foams which have good mechanical properties, good adhesion to
covering
layers and good flame resistance, have good compatibility with blowing agents
and
flame retardants and are readily processable.
The object has surprisingly been able to be achieved by a process for
producing rigid
polyurethane foams by reacting
a) polyisocyanates with
b) compounds having at least two hydrogen atoms which are reactive toward
isocya-
nate groups in the presence of
c) blowing agents,
wherein the compounds b) having at least two hydrogen atoms which are reactive
to-
ward isocyanate groups comprise at least one aromatic polyester alcohol bi),
at least
one polyether alcohol bii) having a functionality of from 4 to 8 and a
hydroxyl number in
the range from 300 to 600 mg KOH/g.
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2a
The invention accordingly provides a process for producing rigid polyurethane
foams
by reacting
a) polyisocyanates with
b) compounds having at least two hydrogen atoms which are reactive toward
isocya-
nate groups in the presence of
c) blowing agents,
wherein the compounds b) having at least two hydrogen atoms which are reactive
to-
ward isocyanate groups comprise at least one aromatic polyester alcohol bi),
at least
one polyether alcohol bii) having a functionality of from 4 to 8 and a
hydroxyl number in
the range from 300 to 600 mg KOH/g.
The invention accordingly provides a process for producing rigid polyurethane
foams
by reacting a) polyisocyanates with b) compounds having at least
two
hydrogen atoms which are reactive toward isocyanate groups in the presence of
c) blowing agents, in the presence of flame retardants d), wherein
the com-
pounds b) having at least two hydrogen atoms which are reactive toward
isocyanate
groups comprise - at least one
aromatic polyester alcohol bi) prepared using at
least one fatty acid, - at least one polyether alcohol bii) having a
functionality of from
4 to 8 and a hydroxyl number in the range from 300 to 600 mg KOH/g, and -
at
least one polyether alcohol biii) having a functionality of from 2 to 4 and a
hydroxyl
number in the range from 100 to < 300 mg KOH/g, where the weight ratio of the
com-
ponent bi) to the sum of the components bii) and biii) is less than 4 and
greater than
0.15.
The invention accordingly provides a rigid polyurethane foam produced
according to
the processes herein described.
The hydroxyl number is determined in accordance with DIN 53240.
The hydroxyl number of the component b) is preferably at least 175 mg KOH/g,
in par-
ticular at least 225 mg KOH/g.
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Furthermore, the hydroxyl number of the component b) is preferably not more
than
325 mg KOH/g, particularly preferably not more than 300 mg KOH/g, in
particular not
more than 290 mg KOH/g.
The polyester alcohol bi) preferably has a functionality of 2-3 and a hydroxyl
number of
from 200 to 300 mg KOH/g.
The polyester alcohol bi) is usually prepared by reacting carboxylic acids
and/or deriva-
tives thereof, in particular esters and anhydrides, with alcohols. The
carboxylic acids
and/or the alcohols, preferably both, are polyfunctional.
In an embodiment of the invention, the polyester alcohol bi) is prepared using
at least
one fatty acid or a fatty acid derivative, preferably a fatty acid.
The fatty acids can comprise hydroxyl groups. Furthermore, the fatty acids can
com-
prise double bonds.
In an embodiment of the invention, the fatty acid does not comprise any
hydroxyl
groups. In a further embodiment of the invention, the fatty acid does not
comprise any
double bonds.
The average fatty acid content of the component b) is preferably greater than
1% by
weight, more preferably greater than 2.5% by weight, more preferably greater
than 4%
by weight and particularly preferably greater than 5% by weight, based on the
weight of
the components b) and d).
The average fatty acid content of the component b) is preferably less than 30%
by
weight, more preferably less than 20% by weight, based on the total weight of
the
components b) and d).
The fatty acid or fatty acid derivative is preferably a fatty acid or fatty
acid derivative
based on renewable raw materials, selected from the group consisting of castor
oil,
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polyhydroxy fatty acids, ricinoleic acid, hydroxyl-modified oils, grapeseed
oil, black
cumin oil, pumpkin kernel oil, borage seed oil, soybean oil, wheatgerm oil,
rapeseed oil,
sunflower oil, peanut oil, apricot kernel oil, pistacchio oil, almond oil,
olive oil, macada-
mia nut oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut
oil, primrose
oil, wild rose oil, safflower oil, walnut oil, hydroxyl-modified fatty acids
and fatty acid
esters based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid,
petroselic
acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic
acid, steridonic
acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid.
Preference is given to using oleic acid as fatty acid.
As described above, the polyester alcohol bi) is prepared using aromatic
carboxylic
acids or anhydrides thereof. In particular, these are selected from the group
consisting
of terephthalic acid, phthalic acid and phthalic anhydride.
In an embodiment of the invention, the polyester alcohol bi) is prepared using
esters of
aromatic carboxylic acids. In particular, these are selected from the group
consisting of
polyethylene terephthalate and dimethyl terephthalate. The polyethylene
terephthalate
can be a recycling product, in particular from the recycling of beverage
bottles.
The polyester alcohol bi) is particularly preferably obtained using mixtures
of carboxylic
acids and derivatives thereof which comprise at least 50% by weight, based on
the
weight of the carboxylic acids, of terephthalic acid. In a further preferred
embodiment of
the invention, exclusively terephthalic acid is used as carboxylic acid.
Apart from the abovementioned carboxylic acids and derivatives thereof, it is
also pos-
sible to use other known polyfunctional carboxylic acids, for example
aliphatic carbox-
ylic acids such as adipic acid or succinic acid. However, the content of these
should be
below 50% by weight, based on the weight of the carboxylic acids.
As alcohols for preparing the polyester alcohols bi), use is usually made of
bifunctional
alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol,
propylene gly-
col, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-
methyl-1,3-
propanediol, 3-methyl-1,5-pentanediol and alkoxylates thereof, in particular
ethoxylates
thereof. In particular, the aliphatic diol is diethylene glycol.
In an embodiment of the invention, the polyester alcohol bi) has a content of
compo-
nents having a functionality of > 2.9 of at least 200 mmol/kg of polyester
alcohol, pref-
erably at least 400 mmol/kg, particularly preferably at least 600 mmol/kg,
especially at
least 800 mmol/kg and in particular at least 1000 mmol/kg of polyester
alcohol. Particu-
lar preference is given to the hydroxyl-comprising components used in the
esterifica-
tion. These are preferably more than bifunctional alcohols, higher-functional
polyols
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PF 70710
selected from the group consisting of glycerol, alkoxylated glycerol,
trimethylolpropane,
alkoxylated trimethylolpropane, pentaerythritol and alkoxylated
pentaerythritol.
In a further preferred embodiment of the invention, the component b)
additionally corn-
5 prises at least one polyether alcohol biii) having a functionality of
from 2 to 4 and a hy-
droxyl number in the range from 100 to < 300 mg KOH/g.
The polyether alcohols bii) and biii) are usually prepared by addition of
alkylene oxides
onto H-functional starter substances. This process is generally known and is
routine for
the preparation of such products.
As starter substances, it is possible to use alcohols or amines. As amines, it
is possible
to use aliphatic amines such as ethylenediamine. In another embodiment of the
inven-
tion, aromatic amines, in particular toluenediamine (TDA) or mixtures of
diphenylme-
thanediamine and polyphenylenepolymethylenepolyamines can be used. The compo-
nent b) preferably comprises not more than 65% by weight, more preferably not
more
than 40% by weight, in each case based on the weight of the component a), of
poly-
ether alcohols based on aromatic amines.
.. In a particularly preferred embodiment of the invention, the component b)
does not
comprise any polyether alcohols based on aliphatic or aromatic amines.
Thus, polyfunctional alcohols are preferred as H-functional starter substances
for the
preparation of the polyether alcohols bii) and biii).
These are, in particular, 2- to 8-functional alcohols. Examples are glycols
such as eth-
ylene glycol or propylene glycol, glycerol, trimethylolpropane,
pentaerythritol and also
sugar alcohols such as sucrose or sorbitol. Mixtures of alcohols with one
another are
also possible. The solid starter substances such as sucrose and sorbitol, in
particular,
are frequently mixed with liquid starter substances such as glycols or
glycerol.
2- to 3-functional alcohols, in particular glycerol or trimethylolpropane, are
preferably
used for preparing the polyols biii). To increase the functionality, higher-
functional alco-
hols can also be added in small amounts.
To prepare the polyols bii), preference is given to using mixtures of high-
functionality
alcohols and the abovementioned alcohols which are liquid at room temperature,
in
particular glycerol. As high-functionality alcohols, preference is given to
using sugar
compounds such as glucose, sorbitol, mannitol and sucrose, polyhydric phenols,
resols
such as oligomeric condensation products of phenol and formaldehyde and
Mannich
condensates of phenols, formaldehyde and dialkanolamines and also melamine.
Par-
ticular preference is given to sugar alcohols, in particular sucrose or
sorbitol.
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It has been found that the use of sorbitol-initiated polyether alcohols brings
advantages
in the processing and the properties of the foams. Thus, better curing and
improved
compressive strength are obtained.
As alkylene oxides, preference is given to using ethylene oxide, propylene
oxide or
mixtures of these compounds. Particular preference is given to using pure
propylene
oxide.
The addition of the alkylene oxides onto the starter substance is preferably
carried out
in the presence of catalysts. Basic compounds are usually used as catalysts,
with the
oxides and in particular the hydroxides of alkali metals or alkaline earth
metals having
attained the greatest industrial importance. Potassium hydroxide is usually
used as
catalyst.
In one embodiment of the invention, amines are used as catalysts for preparing
the
polyether alcohols bii) and bill), in particular the polyether alcohols bii).
These are pref-
erably amines having at least one tertiary amino group, imidazoles, guanidines
or de-
rivatives thereof. These amine catalysts preferably have at least one group
which is
reactive toward alkylene oxides, for example a primary or secondary amino
group or,
particularly preferably, a hydroxyl group. These catalysts are particularly
preferably
amino alcohols such as dimethylethanolamine. Such catalysts are used
particularly
when starter substances comprising sucrose are employed.
In a preferred embodiment of the invention, the weight ratio of the component
bi) to the
sum of the components bii) and biii) is less than 4.
Furthermore, the weight ratio of the component bi) to the sum of the
components bii)
and biii) is preferably greater than 0.15.
As blowing agents, it is possible to use chemical and physical blowing agents.
Chemi-
cal blowing agents are compounds which react with isocyanate groups to
eliminate
gases, in particular carbon dioxide or carbon dioxide and carbon monoxide.
These are
usually water and/or formic acid, preferably water.
In place of or in combination with the chemical blowing agents, it is also
possible to use
physical blowing agents. These are compounds which are inert toward the
starting
components and are usually liquid at room temperature and vaporize under the
condi-
tions of the urethane reaction. The boiling point of these compounds is
preferably be-
low 50 C. The physical blowing agents also include compounds which are gaseous
at
room temperature and are introduced under pressure into the starting
components or
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7
are dissolved therein, for example carbon dioxide, low-boiling alkanes and
fluoroal-
kanes.
The blowing agents are usually selected from the group consisting of water,
formic ac-
.. id, alkanes and cycloalkanes having at least 4 carbon atoms, dialkyl
ethers, esters,
ketones, acetals, fluoroalkanes having from 1 to 8 carbon atoms and
tetraalkylsilanes
having from 1 to 3 carbon atoms in the alkyl chain, in particular
tetramethylsilane.
Mention may be made by way of example of propane, n-butane, isobutane and
cyclo-
butane, n-pentane, isopentane and cyclopentane, cyclohexane, dimethyl ether,
methyl
ethyl ether, methyl butyl ether, methyl formate, acetone and also
fluoroalkanes which
can be degraded in the troposphere and therefore do not damage the ozone
layer, e.g.
trifluoromethane, difluoromethane, 1,3,3,3-pentafluoropropene, 1,1,1,3,3-
pentafluorobutane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2-tetrafluoroethane,
1,1,1,2,3-
pentafluoropropene, 1-chloro-3,3,3-trifluoropropene, difluoroethane and
heptafluoro-
propane. The physical blowing agents mentioned can be used either alone or in
any
combinations with one another.
Particularly preferred physical blowing agents are fluoroalkanes and/or
hydrocarbons.
The blowing agent component c) is usually used in an amount of from 2 to 45%
by
weight, preferably from 2 to 30% by weight, particularly preferably from 2 to
20% by
weight, based on the total weight of the components b) to e).
In a preferred embodiment, the blowing agent mixture c) comprises exclusively
hydro-
carbons as physical blowing agent. Particularly preferred hydrocarbons are n-
pentane,
cyclopentane, isopentane and mixtures of the isomers. In particular, a mixture
of n-
pentane and isopentane is used as physical blowing agent c).
In a preferred embodiment of the invention, a flame retardant d) is
additionally used.
The flame retardant d) is preferably used in an amount of from 10 to 55% by
weight,
based on the total weight of the components b) and d).
The flame retardant d) can comprise hydrogen atoms which are reactive toward
isocy-
anate groups. In a preferred embodiment of the invention, the flame retardant
does not
comprise any hydrogen atoms which are reactive toward isocyanate groups.
Preference is given to using flame retardants d) which comprise at least one
phospho-
rus atom in the molecule.
They can preferably be the products characterized in more detail below.
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A preferred group comprises phosphorus-comprising compounds having a molecular
weight of less than 400 g/mol, especially less than 300 g/mol, preferably less
than
200 g/mol and particularly preferably in the range from 150 to 190 g/mol, and
less than
4 phosphorus atoms, especially less than 3 phosphorus atoms, more especially
less
than 2 phosphorus atoms and in particular 1 phosphorus atom, in the molecule.
Prefer-
ence is given to phosphonates and/or phosphates. Particular preference is
given to
using phosphates and phosphonates selected from the group consisting of
diethyl
ethanephosphonate (DEEP), dimethyl propylphosphonate (DMPP) and triethyl phos-
phate (TEP), particularly preferably from the group consisting of diethyl
ethane phos-
phonate (DEEP) and triethyl phosphate (TEP) and in particular diethyl
ethanephospho-
nate (DEEP). These compounds are preferably used in an amount of from 5 to 40%
by
weight, based on the sum of the masses of b) and d).
A further preferred group of phosphorus-comprising compounds comprises
compounds
of this type having a molecular weight of greater than 300 g/mol. These
preferably have
at least one phosphorus atom in the molecule. Preference is given to
phosphonates
and/or phosphates, especially phosphates. Preference is given to using
diphenyl cresyl
phosphate (DPC) and/or triphenyl phosphate, in particular diphenyl cresyl
phosphate.
These compounds are preferably used in an amount of from 10 to 30% by weight,
based on the sum of the masses of b) and d).
As regards the other compounds used for the process of the invention, the
following
details may be provided:
As polyisocyanates a), use is made of the customary aliphatic, cycloaliphatic
and in
particular aromatic diisocyanates and/or polyisocyanates. Preference is given
to using
tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and in
particular mix-
tures of diphenylmethane diisocyanate and polyphenylenepolymethylene
polyisocya-
nates (crude MDI). The isocyanates can also be modified, for example by
incorporation
of uretdione, carbamate, isocyanurate, carbodiimide, allophanate and in
particular ure-
thane groups.
In particular, crude MDI is used for producing rigid polyurethane foams.
In the prior art, it is customary, if appropriate, to incorporate isocyanurate
groups into
the polyisocyanate. The formation of isocyanurate groups leads to an
improvement in
the flame resistance of the foams. The isocyanurate groups are preferably
formed by
addition of specific catalysts during the reaction to produce the foam.
Furthermore, the component b) can optionally comprise chain extenders and/or
cross-
linkers. Chain extenders and/or crosslinkers used are, in particular,
bifunctional or tri-
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9
functional amines and alcohols, in particular diols and/or triols having
molecular
weights of less than 400, preferably from 60 to 300.
In addition to the components a) to d), the customary catalysts, foam
stabilizers and
auxiliaries and/or additives can be used.
As catalysts, preference is given to using tertiary amines, tin catalysts or
alkali metal
salts. It is also possible to allow the reactions to proceed without
catalysis. In this case,
the catalytic activity of amine-initiated polyols is exploited. Catalysts
which catalyze the
formation of isocyanurate groups include carboxylates of alkali metals.
Foam stabilizers are substances which promote the formation of a regular cell
structure
during foam formation.
Examples which may be mentioned are: silicone-comprising foam stabilizers such
as
siloxane-oxyalkylene copolymers and other organopolysiloxanes. Also
alkoxylation
products of fatty alcohols, oxo alcohols, fatty amines, alkylphenols,
dialkylphenols, al-
kylcresols, alkylresorcinol, naphthol, alkylnaphthol, naphthylamine, aniline,
alkylaniline,
toluidene, bisphenol A, alkylated bisphenol A, polyvinyl alcohol and also
further alkoxy-
lation products of condensation products of formaldehyde and alkylphenols,
formalde-
hyde and dialkylphenols, formaldehyde and alkylcresols, formaldehyde and
alkylresor-
cinol, formaldehyde and aniline, formaldehyde and toluidene, formaldehyde and
naph-
thol, formaldehyde and alkylnaphthol and also formaldehyde and bisphenol A. As
alkoxylation reagents, it is possible to use, for example, ethylene oxide,
propylene ox-
ide, polyTHF and higher homologues.
Further details regarding the abovementioned and further starting materials
may be
found in the specialist literature, for example Kunststoffhandbuch, Volume
VII, Polyure-
thane, Carl Hanser Verlag, Munich, Vienna, 1st, 2nd and 3rd editions 1966,
1983 and
1993.
To produce the rigid polyurethane foams, the polyisocyanates a) and the
components
b) to d) and also the other compounds used for the production of the
polyurethanes are
reacted in such amounts that the isocyanate index of the foam is from 90 to
350, pref-
erably from 100 to 250, more preferably from 110 to 200 and especially from
120 to
200, and in particular from 160 to 200.
The rigid polyurethane foams can be produced batchwise or continuously with
the aid
of known processes, for example by means of the double belt process.
Particular pref-
.. erence is given to processing of the rigid polyurethane foams according to
the invention
by means of a continuous double belt.
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It has been found to be particularly advantageous to employ the two-component
pro-
cess and combine the compounds having at least two hydrogen atoms which are
reac-
tive toward isocyanate groups with the blowing agents, foam stabilizers and
flame re-
tardants and also the optional catalysts and auxiliaries and/or additives to
form a polyol
5 component and react this with the polyisocyanates or mixtures of the
polyisocyanates
and optionally blowing agents, also referred to as isocyanate component.
The rigid polyurethane foams of the invention have good mechanical and
processing
properties. They adhere very well to the surface of the substrates.
Furthermore, they
10 have good flame resistance.
The invention is illustrated by the following examples.
Starting materials
Polyesterol 1: Esterification product of phthalic anhydride, diethylene glycol
and mo-
noethylene glycol having a hydroxyl functionality of 2.0 and a hydroxyl number
of
240 mg KOH/g
Polyesterol 2: Esterification product of terephthalic acid, diethylene glycol,
trime-
thylolpropane and oleic acid having a hydroxyl functionality of 2.3 and a
hydroxyl num-
ber of 245 mg KOH/g
Polyetherol 1: Polyether polyol having a hydroxyl number of 490 mg KOH/g,
prepared
by polyaddition of propylene oxide onto a sucrose/glycerol mixture as starter
molecule
Polyetherol 2: Polyether polyol having a hydroxyl number of 490 mg KOH/g,
prepared
by polyaddition of propylene oxide onto a 72% strength aqueous sorbitol
solution as
starter molecule
Polyetherol 3: Polyether polyol having a hydroxyl number of 160 mg KOH/g,
prepared
by polyaddition of propylene oxide onto trimethylolpropane
Polyetherol 4: Polyether polyol prepared by polyaddition of ethylene oxide
onto eth-
ylene glycol and having a hydroxyl functionality of 2 and a hydroxyl number of
190 mg
KOH/g
Polyetherol 5: Polyether polyol prepared by polyaddition of propylene oxide
onto pro-
pylene glycol and having a hydroxyl functionality of 2 and a hydroxyl number
of 104 mg
KOH/g
TCPP: tris-2-chloroisopropyl phosphate
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Stabilizer: Niax Silicone L 6635 (silicone-comprising stabilizer) from
Momentive
B component
Polymeric MDI (Lupranat M50) having an NCO content of 31% and a viscosity of
500 mPas at 25 C.
Additives
DMCHA Dimethylcyclohexylamine
Catalyst 2: 47% strength potassium acetate solution in 95% strength
monoethylene
glycol
Water
5.5 parts of an n-pentane/isopentane mixture in a ratio of 80:20
Measurement methods:
Curing
Curing was determined by means of the indentation test. For this purpose, a
steel in-
denter having a hemispherical end having a radius of 10 mm was pressed by
means of
a tensile/compressive testing machine to a depth of 10 mm into the foam body
formed
at times of 2.5, 3, 4, 5, 6 and 7 minutes after mixing of the components in a
polystyrene
cup. The maximum force in N required for this is a measure of the curing of
the foam.
As a measure of the brittleness of the rigid polyisocyanurate foam, the time
at which
the surface of the rigid foam had visible fracture zones during the
indentation test was
determined.
Flame resistance
The flame height was measured in accordance with EN ISO 11925-2.
The hydroxyl numbers were determined in accordance with DIN 53240.
Adhesion:
The adhesion was determined by means of a peel adhesion test. For this
purpose, a
test specimen was produced in a closed box mold which had the dimensions 200
mm x
200 mm x 200 mm and whose temperature could be controlled. The test specimen
is
produced in such away that the foam has a degree of compaction of 1.15 0.3.
In
addition, an aluminum-coated paper is placed in the bottom before foaming.
After 5
minutes, the test specimen is removed from the mold. After storage for 24
hours, the
aluminum paper on the underside is cut with parallel cuts with the aid of a
template.
The parallel strip is pulled off to a distance of about 3 cm and clamped in a
testing de-
vice in a Zwick tensile testing machine. The tensile testing machine then
pulls the foil
strip off at a uniform speed of 100 mm/min. A force transducer is integrated
into the
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12
tensile apparatus to measure the force required for pulling off the foil and
thus the peel
adhesion value.
The peel adhesion values indicated below are the arithmetic mean of 2
independent
repeat tests.
Flexural strength:
The flexural strength was determined by means of a 3-point bending test using
a meth-
od based on DIN 53423. Three test specimens having the dimensions 120 mm x 25
mm x 20 mm are sawn from a foam cube having an edge length of 20 cm. In the
bend-
ing test, the test specimen is positioned on two supports having a spacing of
100 mm
and a single force F is applied in the middle. As measurement results, the
flexure and
also the force at fracture or at 20 mm flexure are determined. The flexural
strength is
calculated therefrom as the ratio of bending moment in the middle of the test
specimen
at fracture and the resistance moment of its cross section.
Production of the rigid polyurethane foams
The isocyanates and the components which are reactive toward isocyanate were
foamed together with the blowing agents, catalysts and all further additives
at a con-
stant molar ratio of OH to NCO functions of 100:153 +/- 6. A constant fiber
time of 49
+/- 1 seconds was in each case set by varying the amount of DMCHA and an
overall
foam density of 38.5 +/- 1 WI was in each case set by varying the amount of
water. The
amount of catalyst 2 was kept constant at 1.5% by weight and that of pentane
was kept
constant at 5.5% by weight, based on 100% by weight of the mixture of the
polyester
alcohols and polyether alcohols and the flame retardant and stabilizer and
also 0.5 part
of water.
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Table 1: Effect of an excessively high hydroxyl number of the polyol mixture
Example 1 Comparative example 1
Polyesterol 2 39 16
Polyetherol 1 27.5 50.5
Polyetherol 4 5.5 5.5
Polyetherol 5
TCPP 25 25
Water 0.5 0.5
Stabilizer 2.5 2.5
Polyol OHN 271 328
B2 determination
[cm]
value 11 15
2nd value 9 16
3rd value 10 15
¨4th value 11 16
B2 mean [cm] 10.25 15.5
Table 1 shows that excessively high OH numbers of the polyol component have an
adverse effect on the flame resistance.
Table 2: Effect of an excessively low hydroxyl number of the polyol mixture or
the ab-
sence of a polyether alcohol bii)
Comparative Comparative Comparative
Example 1 example 2 example 3 example 4
Polyesterol 2 39 , 39 72 66.5
Polyetherol 1 27.5
Polyetherol 4 5.5 5.5 5.5 ,
Polyetherol 5 27.5
TCPP 25 25 25 25
Water 0.5 0.5 0.5 0.5 ,
Stabilizer 2.5 2.5 2.5 2.5
Polyol OHN 271 165 208 204
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Indentation
test [N]
2.5 min 47 19 30 34
3 min 61 , 23 38 43
4 min 80 30 55 58
min 97 37 67 69
6 min 108 42 73 82
7 min 119 46 84 88
Peel adhe-
sion [N] 9.4 5.8 5.2 3.8
Table 2 shows that excessively low OH numbers of the polyol component or the
ab-
sence of the polyether alcohol bii) have an adverse effect on the peel
adhesion and
curing.
5
Table 3: Effect of the use of a polyether alcohol having a low functionality
and a low
hydroxyl number
Example 1 Example 5
Polyesterol 2 39 39
Polyetherol 1 27.5 33
Polyetherol 3
Polyetherol 4 5.5
Polyetherol 5
TCPP 25 25
Water 0.5 0.5
Stabilizer 2.5 2.5
Polyol OHN 271 288
B2 determina-
tion [cm]
1stva1ue 11 12
2nd value 9 13
3rd value 10 12
41h value 11 14
B2 mean [cm] 10.25 12.75
Peel adhesion
[N] 9.4 8.7
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Table 3 shows that the use of a low-functionality polyether having a low
hydroxyl num-
ber in the polyol component improves the fire resistance and peel adhesion of
the
foam.
5
Table 4: Effect of the use of an oleic acid-based polyester alcohol
Example 2 Example 6
Polyesterol 1 39.5
Polyesterol 2 , 39
Polyetherol 1 22.5 27.5
Polyetherol 3 5 5
Polyetherol 4 5.5
TCPP 25 25
Water 0.5 0.5
Stabilizer 2.5 2.5
B2 determi-
nation [cm]
1s, value 12 12
2nd value 12 13
3rd value 10 13
4th value 11 12
B2 mean 11.25 12.5
Peel adhe-
sion [N] 9.3 5.9
Table 4 shows that the use of an oleic acid-based ester significantly improves
the ad-
hesion. Furthermore, this table shows that the use of a terephthalic acid-
based ester
10 significantly improves the burning behavior.
Table 5: Effect of the use of a sorbitol-initiated polyether alcohol
Example 1 according to the invention Comparative example 7
Polyesterol 2 39 39
Polyetherol 1 27.5
Polyetherol 2 27.5
Polyetherol 4 5.5 5.5
TCPP 25 25
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Water 0.5 0.5
Stabilizer 2.5 2.5
Polyol OHN 271 271
Indentation
test [N]
2.5 min 47 50
3 min 61 65
4 min 80 84
min 97 99
6 min 108 115
7 min 119 116
Flexural
strength
[N/mm2] 0.17 0.21
Table 5 shows that the use of a sorbitol-initiated polyether alcohol in the
polyol compo-
nent improves the curing and the flexural strength.
