Note: Descriptions are shown in the official language in which they were submitted.
CA 02260343 1999-02-11
Production of rigid foams based on isocyanate
The present invention relates to a process for producing rigid
foams based on isocyanate, in which carbon dioxide is used as
sole or additional blowing agent and at least one organosilicon
compound is used as foam stabilizer, and also the use of these
rigid foams as insulation material.
Rigid foams based on isocyanate, in particular polyurethane (PUR)
and isocyanurate foams, have been known for a long time and are
used predominantly for insulation against heat or cold, e.g. in
refrigeration appliances, in building and construction, in hot
water storage tanks and long-distance heating pipes. A summary
overview of the production of such foams is given, for example,
in the Kunststoff-Handbuch, Volume VII, "Polyurethane", 1st
edition 1966, edited by Dr. R. Vieweg and Dr. A. Hochtlen, and
2nd edition, 1983, and also 3rd edition, 1993, edited by Dr. G.
Oertel, (Carl Hanser Verlag, Munich).
The foaming of PUR foams with addition of COz can be carried out
by the gas loading process or by the liquid metering process.
There are already various machine manufacturers which offer such
metering units. These processes can also be employed in the case
of rigid foam systems, but with the disadvantage that the cell
structure is destroyed when the amount of COz added increases. The
cell diameters become larger and less uniform. The frothing
effect forms large voids. The coarsening of the cells and the
void structure :results in loss of the good insulating properties
too.
The machine manufacturers are at present attempting to alleviate.
these deficiencEa by means of structural changes, by developing a
new generation of mixing heads or various techniques for
introducing the C02 (e. g. 18th Synthetic Foam Conference 1997
(Polyurethan-Formteile grenzenlos innovativ), Wiesbaden, R.
Apenburg et al j Cannon Group "Polyurethan mit Fliissig-COZ
sch~umen", pager 213-241).
The other way of: improving the COz compatibility and the degree of
loading of the raw material component is a task for the raw
material manufacturers.
CA 02260343 1999-02-11
2
In the technical journal "Plastics Technology" 09/1996, pages
29-35 (Sherman L.M. "Surfactants & Catalysts Are Matched To
Ozone-Friendly Urethane Foams"), the influences of raw materials
on the foaming of flexible PUR foam using liquid C02 are
discussed. It is established that it is not the selection of
stabilizer, but an appropriate machine technique in the C02
foaming process which leads to good results. Traditional
stabilizers are said to be completely suitable.
In a lecture at Utech 96 (Noakes C.W. / Dow Europe S.A. and
Casagrande G. / Dow Italia S.p.A. "Liquid C02 Blown Foam For
Automotive Flexible Moulding"), various flexible foam
formulations comprising silicone stabilizers are presented
without these and their effects being described.
WO 97/10277 describes the use of various stabilizers. It is
established that stabilizers having an alkylene oxide content of
less than 37% b;y weight are used for producing flexible PUR block
foams foamed using inert gases and their ethylene oxide content
is from 20 to 6~7~ by weight. However, these stabilizers do not
give void-free and homogeneous rigid foams by the C02 foaming
technique.
It is an object of the present invention to produce foams based
on isocyanate, in particular rigid PUR foams, having homogeneous,
fine and void-free cell structures using the C02 foaming technique
with the aid of suitable raw material formulations.
We have found that this object is surprisingly achieved by using
organosilicon compounds having a relative ethylene
oxide/propylene oxide weight ratio of over 70/30 as foam
stabilizer, with the total Si content being greater than or equal.
to 5~ by weight.
The present invention accordingly provides a process for
producing rigid foams based on isocyanate by reacting
a) organic andior modified organic polyisocyanates with
b) at least one: relatively high molecular weight compound
containing at least two reactive hydrogen atoms and, if
desired,
c) low molecular weight chain extenders and/or crosslinkers
in the presence of
CA 02260343 1999-02-11
3
d) carbon dio:!cide as sole or additional blowing agent,
e) foam stabi:Lizers,
f) catalysts and, if desired,
g) further au~ciliaries and/or additives,
wherein at least one organosilicon compound having a relative
ethylene oxide/propylene oxide weight ratio of over 70/30 is used
as foam stabilizer, with the total Si content being greater than
or equal to 5% by weight, based on the weight of the foam
stabilizer or stabilizers used.
The invention further provides for the use of the
isocyanate-based rigid foams produced in this way as insulation
material.
According to th~s invention, at least one organosilicon compound
having a relative ethylene oxide/propylene oxide weight ratio of
over 70/30 is used as foam stabilizer. The ethylene
oxide/propylene oxide ratio is preferably over 90/10,
particularly preferably 100/0. In the latter case, this means
that no propylene oxide is used.
The total Si content of the foam stabilizer is greater than or
equal to 5% by vaeight, preferably greater than or equal to 10% by
weight. As silicon-containing foam stabilizers for the production
according to the: present invention of rigid foams based on
isocyanate, prei:erence is given to using compounds of the
structural formula
40
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4
R2 R2
(R1)3--Si-O S1 O Si-O Si (R5)3
I I
R2 R3
n I
O
I
CHZ
CHZ
x
0
I
CH2
CH - CH3
O
y
R4
m
In this formula, R1, RZ, R4 and R5 are linear or branched alkyl
radicals having from 1 to 3 carbon atoms and R3 is (CHz)P where
p = 1, 2, 3, 4) 5 or 6. The ratio of x to y is greater than 70/30
and the total S:i content is greater than or equal to 5~ by
weight.
In a particular:Ly advantageous embodiment, the commercially
available silicon-containing foam stabilizers from Goldschmidt,
for example Tegostab B 8423 or Tegostab B 8466, and Air Products,
for example Dabc:o~ DC 5103, DabcoO DC 5357 or DabcoO OS 340, are
used, individua::ly or in admixture.
Mixtures of one or more organosilicon compounds can be used as
foam stabilizer:;. Apart from organosilicon compounds, it is also
possible to make: concomitant use of further foam stabilizers
customary in PUF: chemistry, as are mentioned below by way of
example. If further foam stabilizers customary in PUR chemistry
are used) it is necessary according to the present invention for
the Si content of the total foam stabilizer mixture to be within
CA 02260343 1999-02-11
the above-described limits in order to achieve the desired
result.
Any further foam stabilizers employed are used in an amount of at
5 most from 0.5 to 3~ by weight, based on the total weight of the
components (b), (f) and, if used, (c) and (g).
The rigid foams based on isocyanate are produced by reacting
a) organic and/or modified organic polyisocyanates with
b) at least or..e relatively high molecular weight compound
containing at least two reactive hydrogen atoms and, if
desired,
c) low molecular weight chain extenders and/or crosslinkers
in the presence of
d) carbon dioxide as sole or additional blowing agent,
e) foam stabilizers,
f) catalysts and, if desired,
g) further auxiliaries and/or additives,
in a manner knovun per se .
To produce the :rigid foams based on isocyanate by the process of
the present invention, use is made, with the exception of the
foam stabilizers (e), of the starting materials customary in PUR
chemistry, abou~~ which the following may be said by way of
example:
Suitable organic and/or modified organic diisocyanates and/or
polyisocyanates (a) are the aliphatic, cycloaliphatic)
araliphatic and preferably aromatic polyfunctional isocyanates
known per se.
Specific examplEa are: alkylene diisocyanates having from 4 to
12 carbon atoms in the alkylene radical, e.g. dodecane
112-diisocyanai:e, 2-ethyltetramethylene 1,4-diisocyanate,
2-methylpentamel:hylene 1,5-diisocyanate, tetramethylene
1,4-diisocyanatE: and preferably hexamethylene 1,6-diisocyanate,
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6
cycloaliphatic diisocyanates such as cyclohexane 1,3- and
1,4-diisocyanate, and also any mixtures of these isomers,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(IPDI), hexahydrotolylene 2,4- and 2,6-diisocyanate and also the
corresponding isomer mixtures, dicyclohexylmethane 4,4'-, 2,2'-
and 2,4'-diisocyanate and the also the corresponding isomer
mixtures and preferably aromatic diisocyanates and
polyisocyanates such as tolylene 2,4- and 2,6-diisocyanate (-TDI)
and the corresponding isomer mixtures, diphenylmethane 4,4'-,
2,4'-and 2,2'-diisocyanate (-MDI) and the corresponding isomer
mixtures, mixtures of 4,4'- and 2,2'-MDI, polyphenylpolymethylene
polyisocyanates, mixtures of 4,4'-, 2,4'- and 2,2'-MDI and
polyphenylpolymethylene polyisocyanates (crude MDI) and mixtures
of crude MDI and TDI. The organic diisocyanates and
polyisocyanates can be used individually or in the form of their
mixtures.
Use is frequently also made of modified polyfunctional
isocyanates, i.e. products which are obtained by chemical
reaction of organic diisocyanates and/or polyisocyanates.
Examples which may be mentioned are diisocyanates and/or
polyisocyanates containing ester, urea, biuret, allophanate,
isocyanurate and preferably carbodiimide, uretdione and/or
urethane groups. Specific examples of suitable modified
isocyanates are: organic, preferably aromatic polyisocyanates
containing urethane groups and having NCO contents of from 33.6
to 15~ by weight, preferably from 31 to 21% by weight, based on
the total weight, for example 4,4'-MDI modified with low
molecular weight diols, triols, dialkylene glycols, trialkylene
glycols or polyoxyalkylene glycols having molecular weights of up
to 6000, in par~~icular molecular weights up to 1500, modified
4,4'- and 2,4'-IrIDI mixtures or modified crude MDI or 2,4- or
2,6-TDI, with examples of dialkylene or polyoxyalkylene glycols .
which can be usE:d individually or as mixtures being: diethylene
glycol, dipropy:Lene glycol, polyoxyethylene, polyoxypropylene and
polyoxypropylene-polyoxyethylene glycols, triols and/or tetrols.
Also suitable a~.e prepolymers containing urethane groups and
having an NCO content of from 25 to 3.5~ by weight, preferably
from 21 to 14o by weight, or pseudoprepolymers having an NCO
content of from 35 to 14% by weight, preferably from 34 to 22~ by
weight) based on the total weight, prepared by reacting diols,
oxyalkylene glyc:ols and/or polyoxyalkylene glycols having
molecular weight, of from 62 to 6000, preferably the polyether
polyols and/or polyester polyols described below, with TDI,
4,4'-MDI, MDI isomer mixtures and/or crude MDI, e.g. at from 20
to 110°C, preferably from 50 to 90°C. Other modified isocyanates
which have been found to be useful are liquid polyisocyanates
CA 02260343 1999-02-11
7
containing carbodiimide groups and/or isocyanurate rings and
having NCO contents of from 33.6 to 15~ by weight, preferably
from 31 to 21~ by weight) based on the total weight, e.g. those
based on MDI isomers and/or TDI.
The modified polyisocyanate can be mixed with one another or with
unmodified organic polyisocyanates, such as, for example, 2,4'-
and/or 4,4'-MDI, crude MDI, 2,4- and/or 2,6-TDI.
Organic polyisocyanates which have been found to be particularly
useful and are therefore preferably employed are: TDI, 1~I, crude
MDI and their mixtures or mixtures of modified organic
polyisocyanate,s containing urethane groups and having an NCO
content of from 33.6 to 15~ by weight, in particular those based
on TDI, 4,4'-M1~I, MDI isomer mixtures or crude MDI, and in
particular crude MDI having an 1~I isomer content of from 30 to
80~ by weight, preferably from 30 to 55% by weight.
Suitable relatively high molecular weight.compounds containing at
least two reaci:ive hydrogen atoms (b) are compounds which have
two or more reactive groups selected from among OH groups, SH
groups, NH groups, NH2 groups and CH-acid groups, e.g. (3-diketo
groups, in the molecule. Use is advantageously made of those
having a functionality of from 2 to 8, preferably from 2 to 6,
and a molecular- weight of from 300 to 8000, preferably from 400
to 4000.
Compounds which have been found to be useful are, for example,
polyetherpolyamines and/or preferably polyols selected from the
group consisting of polyether polyols, polyester polyols,
polythioether F~olyols, polyesteramides, hydroxyl-containing
polyacetals anc', hydroxyl-containing aliphatic polycarbonates or
mixtures of at least two of the polyols mentioned. Preference is
given to using polyester polyols and/or polyether polyols. The
hydroxyl number of the polyhydroxyl compounds is generally from
100 to 850 and preferably from 200 to 600.
Suitable polyester polyols can be prepared, for example, from
organic dicarboxylic acids having from 2 to 12 carbon atoms,
preferably aliphatic dicarboxylic acids having from 4 to 6 carbon
atoms, and polyhydric alcohols, preferably diols, having from 2
to 12 carbon atoms, preferably from 2 to 6 carbon atoms. Examples
of suitable dicarboxylic acids are: succinic acid, glutaric acid,
adipic acid, suberic acid, azelaic acid, sebacic acid,
decanedicarboxylic acid, malefic acid, fumaric acid, phthalic
acid, isophthalic acid and terephthalic acid. The dicarboxylic
CA 02260343 1999-02-11
8
acids can be u~;ed either individually or in admixture with one
another. In place of the free dicarboxylic acids, it is also
possible to uss: the corresponding dicarboxylic acid derivatives
such as dicarboxylic esters of alcohols having from 1 to 4 carbon
atoms or dicarboxylic anhydrides. Preference is given to using
dicarboxylic acid mixtures of succinic, glutaric and adipic acids
in weight ratios of, for example, 20 - 35 : 35 - 50 . 20 - 32,
and in particular adipic acid. Examples of dihydric and
polyhydric alcohols) in particular diols, are: ethanediol,
diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol,
glycerol and trimethylolpropane. Preference is given to using
ethanediol, dieahylene glycol, 1,4-butanediol, 1,5-pentanediol
and 1,6-hexaned.iol. It is also possible to use polyester polyols
derived from lactones, e.g. s-caprolactone, or hydroxycarboxylic
acids, e.g. cc~-r~ydroxycaproic acid.
To prepare the polyester polyols, the organic, e.g. aromatic and
preferably aliphatic, polycarboxylic acids and/or derivatives and
polyhydric alcohols can be polycondensed in the absence of
catalysts or preferably in the presence of esterification
catalysts, advantageously in an atmosphere of inert gas such as
nitrogen, carbon monoxide) helium, argon, etc., in the melt at
from 150 to 250°C, preferably from 180 to 220°C, under
atmospheric
or subatmospheric pressure to the desired acid number which is
advantageously less than 10, preferably less than 2. According to
a preferred embodiment, the esterification mixture is
polycondensed at the abovementioned temperatures to an acid
number of from 80 to 30, preferably from 40 to 30, under
atmospheric pressure and subsequently under a pressure of less
than 500 mbar) preferably from 50 to 150 mbar. Suitable
esterification catalysts are, for example, iron, cadmium, cobalt,
lead, zinc, antimony, magnesium, titanium and tin catalysts in
the form of metals, metal oxides or metal salts. However, the
polycondensation can also be carried out in the liquid phase in
the presence of diluents and/or entrainers such as benzene,
toluene, xylene or chlorobenzene to azeotropically distil off the
water of condensation.
To prepare the polyester polyols, the organic polycarboxylic
acids and/or derivatives and polyhydric alcohols are
advantageously polycondensed in a molar ratio of 1:1 - 1.8,
preferably 1:1.05 - 1.2. The polyester polyols obtained
preferably have a functionality of from 2 to 4, in particular
from 2 to 3, anti a molecular weight of from 300 to 3000, in
particular from 400 to 600.
CA 02260343 1999-02-11
9
However, polyo7.s used are particularly preferably polyether
polyols which are prepared by known methods, 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 iaopropoxide as catalysts with addition of at least
one initiator molecule containing from 2 to 8, preferably from 2
to 6, 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.
For specific applications, monofunctional initiators can also be
incorporated into the polyether structure.
guitable alkyls:ne 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 oxide:. can be used individually, alternately in
succession or a.s mixtures. Examples of suitable initiator
molecules are: water, organic dicarboxylic acids such as succinic
acid, adipic acid, phthalic acid and terephthalic acid, aliphatic
and aromatic, u.nalkylated, N-mono-alkylated, N,N- and
N,N'-di.alkylats:d diamines having from Z to 4 carbon atoms in the
alkyl radical, e.g. unalkylated, monoalkylated and dialkylated
ethylenediamine, diethylenetriamine, triethylenetetramine,
1,3-propylenedi.amine) 1,3- or 1,4-butylenediamine, 1,2-, 1,3-,
1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,3-,
2,4- and 2,6-tolylenediamine and 4,4'-, 2,4'- and
2,2'-diaminodiphenylmethane. Further suitable initiator molecules
are: alkanolami.nes such as ethanolamine, N-methylethanolamine and
N-ethylethanola.mine, dialkanolamines such as diethanolamine,
N-methyldiethanolamine and N-ethyldiethanolamine, and
trialkanolaminea such as triethanolamine, and ammonia. Preference
is given to using polyhydric, in particular dihydric and/or
trihydric, alcohols such as ethanediol, 1,2- and 2,3-propanediol,
diethylene glycol, dipropylene glycol, 1,4-butanediol,
1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol,
sorbitol and sucrose.
The polyether F~olyols, preferably polyoxypropylene polyols and
polyoxypropyler..~e-polyoxyethylene polyols, have a functionality of
preferably front 2 to 6 and in particular from 2 to 4 and
molecular weights of from 300 to 8000, preferably from 400 to
6000 and in particular from 1000 to 5000, and suitable
polyoxytetramet.hylene glycols have a molecular weight up to about
3500.
CA 02260343 1999-02-11
Further suitable polyether polyols are polymer-modified polyether
polyols, for example graft polyether polyols, in particular those
based on styrene and/or acrylonitrile which are prepared by in
situ polymerization of acrylonitrile) styrene or preferably
5 mixtures of styrene and acrylonitrile, e.g. in a weight ratio of
from 90:10 to 10:90, preferably from 70:30 to 30:70,
advantageously in the abovementioned polyether polyols using
methods similar to those given in the German patents 1111394,
1222669 (US-A-3304273, 3383351, 3523093), 1152536 (GB 1040452)
10 and 1152537 (GH 987618), and also polyether polyol dispersions
which contain as disperse phase, usually in an amount of from 1
to 50~ by weight, preferably from 2 to 25o by weight: e.g.
polyureas, polyhydrazides, polyurethanes containing bound
tertiary amino groups and/or melamine and are described, for
example, in EP-B-011752 (US-A-4304708), US-A-4374209 and
DE-A-3231497.
Like the polyester polyols, the polyether polyols can be used
individually or in the form of mixtures. They can also be mixed
with the graft polyether polyols or polyester polyols or the
hydroxyl-containing polyesteramides, polyacetals, polycarbonates
and/or polyetherpolyamines.
Suitable hydro~:yl-containing polyacetals are, for example, the
compounds which can be prepared from glycols such as diethylene
glycol and trie:thylene glycol,
4,4'-dihydroxyeahoxydiphenyldimethylmethane or hexanediol and
formaldehyde. ~~uitable polyacetals can also be prepared by
polymerization of cyclic acetals.
Suitable hydro~:yl-containing polycarbonates are those of the type
known per se which can be prepared, for example, by reacting
diols such as 1,3-propanediol, 1,4-butanediol and/or
1~6-hexanediol, diethylene glycol, triethylene glycol or
tetraethylene crlycol with diaryl carbonates, e.g. diphenyl
carbonate, or phosgene.
The polyesteramides include, for example, the predominantly
linear condensates obtained from polybasic, saturated and/or
unsaturated carboxylic acids or their anhydrides and
polyfunctional saturated and/or unsaturated aminoalcohols or
mixtures of po7.yfunctional alcohols and aminoalcohols and/or
polyamines.
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11
Suitable polyetherpolyamines can be prepared from the
abovementioned polyether polyols by known methods. Examples which
may be mentioned are the cyanoalkylation of polyoxyalkylene
polyols and subsequent hydrogenation of the nitrile formed
(US-A-3267050) or the partial or complete amination of
polyoxyalkylene polyols using amines or ammonia in the presence
of hydrogen and catalysts (DE-A-1215373).
The rigid foams based on isocyanate can be produced with or
without concomitant use of chain extenders and/or croslinkers
(c). However, the addition of chain extenders, crosslinkers or,
if desired, mixtures thereof can prove to be advantageous for
modifying the mechanical properties, e.g. the hardness. Chain
extenders and/or crosslinkers used are water and also diols
and/or triols having molecular weights of less than 400,
preferably from 60 to 300. Suitable chain extenders/crosslinkers
are, for example, aliphatic, cycloaliphatic and/or araliphatic
diols having from 2 to 14, preferably from 4 to 10, carbon atoms,
e.g, ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-,
p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and
preferably 1,4-butanediol, 1,6-hexanediol and
bis(2-hydroxyethyl)hydroquinone, triols such as 1,2,4-,
1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane, and
low molecular weight hydroxyl-containing polyalkylene oxides
based on ethylene oxide and/or 1,2-propylene oxide and the
abovementioned diols and/or triols and/or pentaerythritol,
sorbitol and sucrose as initiator molecules.
The chain extenders, crosslinkers or mixtures thereof are
advantageously used in an amount of from 0 to 20% by weight,
preferably from 2 to 8% by weight, based on the weight of the
component (b).
As blowing agent (d), use is made according to the present
invention of carbon dioxide, either alone or as additional
blowing agent. 'The physical metering and the loading of the
components with C02 is carried out in a known way. Details may be
found in relevant specialist journals, for example in
"Kunststoffe" 6/97, pages 722-727 (H. Klahre et al:
PUR-Schaumstoffe mit homogener Zellstruktur) and
"Plastverarbeiter" 7/97, pages 46/47 (Perfekt geschaumt). Some
information regarding the introduction of C02 is given below.
Apart from C02, it is possible to use further blowing agents which
are generally k;aown from polyurethane chemistry.
CA 02260343 1999-02-11
12
Apart from chlorofluorocarbons (CFCs), whose use is being greatly
restricted or completely stopped for ecological reasons, use can
be made of, in particular, aliphatic and/or cycloaliphatic
hydrocarbons having up to 12 carbon atoms, in particular butanes,
pentanes cnd c~lclopentane, lower monofunctional alcohols, acetals
such as methylal, or else partially halogenated hydrocarbons
(HCFCs) as alternative blowing agents. Furthermore, it is
advantageous to use perfluoro compounds such as perfluoroalkanes,
preferably n-perfluoropentane, n-perfluorohexane,
n-perfluoroheptane and n-perfluorooctane, as co-blowing agent.
The highly fluorinated and/or perfluorinated.hydrocarbons are
usually emulsi:Eied in the polyol component. If emulsifiers are
employed, use :is made, for example, of oligomeric acrylates which
contain bound polyoxyalkylene and fluoroalkane radicals as side
groups and have a fluorine content of from about 5 to 30% by
weight. Such p:coducts are sufficiently well known from polymer
chemistry.
The physical b:Lowing agents can be used individually or in any
mixtures with one another, as pure isomers or as isomer mixtures.
They are usual:Ly added to the polyol component of the system.
However, they can also be added to the isocyanate component or,
as a combination, both to the polyol component and to the
isocyanate component.
The amount of blowing agent or blowing agent mixture used is from
1 to 25% by weight, preferably from 1 to 20 % by weight, in each
case based on the components (b) to (g).
Furthermore, ii. is possible and customary to add water in an
amount of from 0.5 to 15% by weight, preferably from 1 to 5% by
weight, based on the formative components (b) to (g), as blowing
agent. This ut:Llizes the blowing action of the COz generated by
the isocyanate~-water reaction. The addition of water can be
combined with 1=he use of the other blowing agents described.
As foam stabil:Lzers (e), use is made according to the present
invention of the above-described organosilicon compounds, if
desired in admixture with further foam stabilizers customary in
PUR chemistry. Details of further foam stabilizers which may be
used can be found in the specialist literature, for example the
monograph by J.H. Saunders and K.C. Frisch "High Polymers" Volume
XVI, Polyureth<~nes, Parts 1 and 2, Interscience Publishers 1962
and 1964, and also the above-cited Kunststoff-Handbuch, Volume
VII, "Polyurethane".
CA 02260343 1999-02-11
13
Catalysts (f) used for producing foams based on isocyanate are,
in particular, compounds which strongly accelerate the reaction
of the compounds containing reactive hydrogen atoms, in
particular hydroxyl groups, of the components (b). (c) and (e)
with the organic, modified or unmodified polyisocyanates (a).
Suitable catalysts axe organic metal compounds, preferably
organic tin compounds such as tin(II) salts of organic carboxylic
acids, e.g. tin(II) acetate, tin(II) octoate, tin(II)
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 organic metal compounds are used alone or
preferably in combination with strongly basic amines. Examples
which may be mentioned are amidines such as
2,3-dimethyl-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,
pentamethyldiethylenetriamine, bis(dimethylaminoethyl) ether,
bis(dimethylaminopropyl)urea, dimethylpiperazine,
1,2-dimethylimidazole, 1-azabicyclo(3,3.0]octane and preferably
1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds such as
triethanolamine, triisopropanolamine, N-methyldiethanolamine and
N-ethyldiethanolamine and dimethylethanolamine.
Further suitable catalysts are:
tris(dialkylaminoalkyl)-s-hexahydrotriazines, in particular
tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine,
tetraalkylammonium hydroxides such as tetramethylammonium
hydroxide, alkali metal hydroxides such as sodium hydroxide and
alkali metal al:koxides such as sodium methoxide and potassium
isopropoxide, a:nd also alkali metal salts of long-chain fatty
acids having from 10 to 20 carbon atoms and possibly lateral OH
groups. Preference is given to using from 0.001 to 5% by weight,
in particular from 0.05 to 3% by weight, of catalyst or catalyst
combination, based on the weight of the formative components (b)
to (g) .
If desired, further auxiliaries and/or additives (g) can be
incorporated into the reaction mixture for producing the
polyurethane foams. Examples which may be mentioned are flame
retardants, surface-active substances) cell regulators, fillers,
dyes, pigments, hydrolysis inhibitors, fungistatic and
bacteriostatic substances.
CA 02260343 1999-02-11
14
Suitable flame retardants are, for example, tricresyl phosphate,
tris(2-chloroet:hyl) phosphate, tris(2-chlororopyl) phosphate,
tetrakis(2-chloroethyl) ethylenediphosphate, dimethyl
methanephosphonate, diethyl diethanolaminomethylphosphonate and
also commercial. halogen-containing flame retardant polyols. Apart
from the abovementioned halogen-substituted phosphines, it is
also possible t:o use inorganic or organic flame retardants such
as red phosphorus, hydrated aluminum oxide, antimony trioxide,
arsenic oxide, ammonium polyphosphate and calcium sulfate,
expandable graF~hite or cyanuric acid derivatives such as
melamine, or mixtures of at least two flame retardants such as
ammonium polyphosphates and melamine and also, if desired, maize
starch or ammonium polyphosphate, melamine and expandable
graphite and/or aromatic or aliphatic polyesters for making the
polyisocyanate polyaddition products flame resistant. Additions
of melamine have been found to be particularly effective here. In
general, it has been found to be advantageous to use from 5 to 60
parts by weight, preferably from 10 to 50 parts by weight, of the
flame retardants mentioned per 100 parts by weight of the
formative components (b) to (g).
Further details regarding the abovementioned and other starting
materials may be found in the above-cited specialist literature.
To produce the rigid foams based on isocyanate, the components
(a) to (g) are reacted in such amounts that the equivalence ratio
of the NCO groups of the component (a) to the sum of the reactive
hydrogen atoms of the components (b), (e), (f) and, if used, (c)
and (g) is 0.85 - 1.75:1, preferably 1.0 - 1.3:1. If the rigid
foams based on isocyanate contain at least some bonded
isocyanurate gr~~ups. a ratio of said components of 1.5 - 60:1,
preferably 3 - 'B : 1, is usually employed.
The isocyanate-based rigid foams produced by the process of the
present invention are advantageously produced by the one-shot
process, for example by means of the high-pressure or
low-pressure technique in open or closed molds, for example metal
molds. The continuous application of the reaction mixture to
suitable conveyor belts for producing foam blocks is also
customary.
It has been found to be particularly advantageous to employ the
two-component method and to combine the formative components (b),
(c), (d), (e), (f) and, if used, (g) to form a polyol component,
also referred to as component A, and to use the formative
component (a) and, if desired, blowing agent (d) as isocyanate
CA 02260343 1999-02-11
component, also referred to as component B. The starting
components are mixed at from 15 to 90°C, preferably from 20 to
60°C and in particular from 20 to 35°C, and introduced into the
open mold or under atmospheric or superatmospheric pressure into
5 the closed mold. Mixing can be carried out, for example,
mechanically by means of a stirrer or a stirring screw. The mold
temperature is advantageously from 20 to 110°C, preferably from 30
to 60°C and in particular from 45 to 50°C.
10 The introduction of C02 as blowing agent for foaming is carried
out in a known manner. The following 2 process routes have been
found to be particularly useful:
15 1- Loading the polyol component with C02 gas at pressures of from
4 to 15 bar, preferably from 6 to 10 bar, to a C02 content which
is below the frothing limit of the reaction mixture and needs to
be determined for the respective system as a function of the raw
material compo:~ition of the components. After loading, the polyol
component is mixed with the isocyanate component in a mixing head
and introduced into the mold or applied to a belt for foaming.
2. Liquid COZ as additional component is, in the amounts
determined as described above, either metered via a nozzle
directly into the main components in the mixing head or
introduced by means of a metering unit into a static mixer
immediately upstream of the mixing head and homogeneously mixed
into the polyol component which is then conveyed to the mixing
head.
The rigid PUR foams produced by the process of the present
invention have a density of from 0.02 to 0.75 g/cm3, preferably
from 0.025 to 0.24 g/cm3 and in particular from 0.03 to 0.1 g/cm3.
They are particularly suitable as insulation material for
refrigeration appliances, in building for the insulation of cold
stores, warehouses, long-distance heating pipes, containers and
the like.
The present invention is illustrated by the Examples below.
CA 02260343 1999-02-11
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Example 1 (Com;parison)
The rigid foam formulation was made up using the stabilizer
Tegostab B 8863 (Goldschmidt) having an ethylene oxide/propylene
oxide weight r~3tio of 44/S6, an Si content of 3% by weight, based
on the weight of the stabilizer used, and a hydroxyl number of 34
mg KOH/g:
A component:
55.5% by weight of a polyhydroxyl compound prepared from
sucrose, glycerol and propylene oxide and having
a
hydroxyl number of 423 mg KOH/g,
20.0% b5~ weight of a Br-, Cl- and P-containing flame
rsaardant mixture having a Br content of 34% by
weight, a C1 content of 11% by weight, a P content
of
3~c by weight and a hydroxyl number of 210 mg KOH/g,
20.0% by weight of trischloropropyl phosphate,
1.0% by weight of tris(dimethylaminopropyl)-s-
he.xahydrotriazine,
0.5% by weight of triethylamine (TEA),
2.0% by weight of water and
1.0% by weight of Si stabilizer Tegostab B 8863
(Goldschmidt)
B component:
Polyisocyanate Lupranat0 M 50 (BASF), viz. a mixture of
diphenylmethane diisocyanate and polyphenyl polyisocyanates
having an NCO content of 31.5% by weight and a viscosity of
S50 mPas at 25°C.
Mixing ratio:
Component A 100 parts by weight
Component B 117 parts by weight
Results after machine foaming using C02 gas and liquid C02
(analogous resu:Lts are obtained by both methods):
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17
C02 addition, '~ by weight 0 0.8 1.2
based on comp. A
Foam density, g/1 62 52 50
Thermal conductivity, mW/mK23.9 23.3 not
measurable*
Cell size, Eun 190/250**190/290 not
measurable*
Number of voids per 400 0 10 57
cm2
* no measurement was possible because of an inhomogeneous cell
structure and large voids
** perpendicu:.ar/parallel to the direction of foaming
The foam had an increasingly poorer homogeneity and
void-containing cell structure with increasing C02 adddition for
both C02 methods. The rigid foam could not be utilized.
Example 2
Example 2 was carried out using the same raw materials and the
same mixing ratio as in Example 1, but the stabilizer Tegostab B
8863 was replaced by a mixture of stabilizers Tegostab B 8466
(G°ldschmidt) a;nd DabcoO OS 340 (Air Products), each in an amount
of 0.5% by weight. The EO/PO ratio of the stabilizer mixture was
81/19%, the Si content was 7% by weight, based on~the weight of
the stabilizer mixture used, and the hydroxyl number was
65 mg KOH/g.
Results after m<~chine foaming using C02 gas and liquid C02:
C02 addition, % by weight 0 0.8 1.2
based on comp. A
Foam density, g/1 61 52 50
Thermal conductivity, mW/m~K23.3 23.3 23.7
Cell size, Eun 180/240 190/250 220/260
Number of voids per 400 0 2 20
cm2
The ridid foam was more fine-celled and had fewer voids than that
in Example 1.
CA 02260343 1999-02-11
18
Example 3
Example 3 was :Likewise carried out using the same raw materials
and the same mixing ratio as in Example 1, but the stabilizer
Tegostab B 886:3 was replaced by the stabilizer Dabco~ DC 5357
(Air Products) in an amount of 1.0% by weight. The EO/PO ratio
was 100/0%, ths: Si content was 16% by weight, based on the weight
of the stabili::er used, and the hydroxyl number was 50 mg KOH/g.
Results after machine foaming using C02 gas and liquid C02:
C02 addition, ~~ by weight,0 0.8 1.2
based on comp. A
Foam density, ~~/1 62 52 51
Thermal conductivity, mW/m~K23.3 23.0 23.2
Cell size, Eun 160/170 180/200 180/230
Number of voids per 400 0 0 0
cm2
25
The rigid foam was fine-celled and continued to have a
homogeneous cell structure after C02 addition. Despite the
frothing effect at 1.2% of C02, there was no formation of voids in
the foam.
Example 4
The following e:~ample demonstrates a rigid foam formulation using
cyclopentane as additional blowing agent. The stabilizer used was
a mixture of Tec~ostab B 8423 and DabcoO DC 5103 having an EO/PO
weight ratio of 74/26, an Si content of 8% by weight and a
hydroxyl number of 91 mg KOH/g:
A component:
54.0% by weight of a polyhydroxyl compound prepared
from
sorbitol and propylene oxide and having a hydroxyl
number of 490 mg KOH/g,
28.0% by weight of a polyhydroxyl compound prepared
from
~:ucrose
and diethylene
glycol and
having a
r.ydroxyl
number of
400 mg KOH/g,
5.3% b~y weight of dipropylene glycol,
1.9% by weight of glycerol,
2.1% by weight of a catalyst mixture of
dimethylcyclohexylamine
and pentamethyldiethylene-
triamine,
CA 02260343 1999-02-11
19
0.8% by weight ofwater,
0.9% by weight ofSi stabilizer Tegostab B
8423,
0.5% by weight ofSi stabilizer DabcoO DC5103
and
6.5% by weight ofcyclopentane
B component:
Polyisocyanate Lupranat~ M 20 (BASF), viz. a mixture of
diphenylmethane diisocyanate and polyphenyl polyisocyanates
having an NCO content of 31.5% and a viscosity of 220 mPas at
25°C.
Mixing ratio:
Component A 100 parts by weight
Component B 143 parts by weight
Results after machine foaming using liquid C02:
C02 addition, '% by weight 0 0.6 1.2
based on comp. A
Foam density, g/1 57.5 51 49.5
Thermal conducaivity, mW/mK21.2 21.4 21.6
Cell size, E.tm 307/320**270/290 290/330
Number of voids per 400 0 5 10
cm2
** perpendicular/parallel to the direction of foaming
The foam had a finer cell structure with increasing COZ addition.
Void formation was significantly less than in Example 1. .
Example 5
Example 5 was carried out using the same raw materials and the
same mixing ratio as in Example 4, but the stabilizer mixture was
replaced by the: stabilizer Dabco~ DC 5357 (Air Products). The Si
content of the stabilizer based on 100% by weight of EO was thus
increased to 16% by weight.
Results after machine foaming using liquid COZ:
CA 02260343 1999-02-11
C02 addition, 9's by weight,0 0.6 1.2
based on comp. A
Foam density, ~~/1 57.5 51 49
Thermal conductivity, mW/mK20.8 21.0 21.2
5 Cell size, Eun 190/220 240/260 270/310
Number of voids per 400 0 1 5
cm2
10 The rigid foam was more fine-celled and had fewer voids than that
in Example 4.
20
30
40
