Polyurethane foams modified with nonionic surfactants

A polyurethane composition for the production of single-component polyurethane foams on dry or wet substrates, wherein the composition is the reaction product of a polyol with a molar excess of difunctional or polyfunctional isocyanates and wherein 10% to 80% by weight of the polyol has been replaced by a nonionic surfactant containing at least one hydroxyl group.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates to new polyurethane compositions modified with 
hydrophilic surfactants containing isocyanate-reactive functional groups 
for the production of fine-cell homogeneous polyurethane foams. 
DISCUSSION OF RELATED ART 
Prior Art 
Polyurethane foams, more especially so-called one-component polyurethane 
foams, are known for example from Ullmanns Enzyklopadie der technischen 
Chemie, 4th Edition, Vol. 19, pages 317 et seq., Verlag Chemie, Weinheim. 
The foams in question are mixtures of isocyanate-terminated reaction 
products of polyols with difunctional or polyfunctional isocyanates, 
catalysts to accelerate the reaction, viscosity-reducing agents, blowing 
agents and other auxiliaries which--protected against moisture--are 
marketed in pressurized containers. When they are released from the 
pressurized containers, the mixtures foam through evaporation of the 
blowing agent and cure under the effect of moisture from the surrounding 
environment or from the atmosphere. Polyurethane foams are used, for 
example, for insulating domestic appliances, as an insulating material and 
for filling joints with foam in the building industry and as insulating 
materials. 
They essentially contain polyols bearing several OH groups in the molecule, 
difunctional or polyfunctional isocyanates, blowing agents, flame-proofing 
agents and auxiliaries, such as catalysts and stabilizers. 
The polyols used may be any of the polyether or polyester polyols typically 
used in polyurethane chemistry. A review of possible polyols can be found 
in Ullmanns Enzyklopadie der technischen Chemie, 4th Edition, Vol. 19, 
pages 304-5, Verlag Chemie, Weinheim. The production of inexpensive 
oleochemical polyols from renewable raw materials and their use for this 
purpose is also known, cf. German patent applications DE-A1 36 26 223 and 
DE-A1 41 28 649. The first application claims prepolymers based on 
oleochemical polyols which are obtained by ring opening of epoxidized 
triglycerides with alcohols and subsequent partial transesterification. 
The second application describes the lithium-salt-catalyzed ring opening 
of epoxides with nucleophiles, such as alcohols, optionally in conjunction 
with subsequent transesterification of the reaction products with other 
non-epoxidized triglycerides. 
Hitherto, chlorofluorocarbons (CFC's) have often been used as blowing 
agents. On account of ecological objections to these compounds which 
damage the ozone layer, so-called partly halogenated hydrocarbons (HCFC's) 
which are less damaging to the ozone layer, for example 
difluorochloromethane, difluorochloroethane, dichlorofluoroethane or 
tetrafluoroethane, have recently been used to an increasing extent as 
blowing agents. It is also known that fluorine-containing blowing agents 
need not be used at all, being replaced for example by dimethyl ether, 
propane or isobutane. 
The use of more highly fluorinated or CFC-free blowing agents or 
oleochemical polyols, which is actually desirable from the ecological 
point of view, results in hydrophobicization of the polyurethane 
compositions. As a result, the water which is absolutely essential for the 
crosslinking and curing of the polyurethane compositions to form foams is 
unable adequately to penetrate through the foam. This results in the 
formation of voids in the foam and in unwanted shrinkage of the foam after 
setting. To avoid this, both the substrate and the foam itself have to be 
thoroughly moistened during processing of the foams. Voids occur in 
greater numbers when the polyurethane foams are applied to dry substrates. 
The formation of voids and shrinkage are technically undesirable and 
complicate or prevent application of the ecologically more favorable 
polyurethane foams. 
Accordingly, the problem addressed by the present invention was to provide 
polyurethane foams, more especially based on oleochemical polyols and/or 
free from CFC-containing blowing agents, which would give fine-cell, 
homogeneous and substantially void-free foams without moistening of the 
substrate and/or the foam. 
Another problem addressed by the invention was to improve the permeability 
of polyurethane foams to water and water vapor. 
In addition, the stability of the polyurethane compositions packed in 
pressurized containers against precipitation, above all at low 
temperatures, would remain guaranteed. 
DESCRIPTION OF THE INVENTION 
According to the invention, the solution to this problem is characterized 
in that the polyols used for production are partly replaced by hydrophilic 
surfactants containing isocyanate-reactive functional groups. 
Accordingly, the present invention relates to polyurethane compositions for 
the production of one-component polyurethane foams containing reaction 
products of polyols with a molar excess of difunctional or polyfunctional 
isocyanates, characterized in that 10 to 80% by weight of the polyols are 
replaced by nonionic surfactants containing at least one hydroxyl group. 
Nonionic Surfactants 
Surfactants in the context of the present invention are compounds which 
consist of one or more hydrophobic groups and one or more nonionic 
hydrophilic groups. 
The hydrophobic groups are preferably optionally substituted hydrocarbon 
radicals. Polyethylene oxide or polyglycerol groups are mentioned as 
examples of nonionic hydrophilic groups. 
Suitable surfactants are those which, in addition to the hydrophilic group, 
contain an isocyanate-reactive functional group such as, for example, 
fatty alcohol ethoxylates, alkylphenol ethoxylates, fatty acid amide 
ethoxylates, fatty acid amine ethoxylates, alkoxylated OH-functional 
triglycerides, alk(en)yl oligoglycosides, fatty acid glucamides or partial 
esters of polymerized glycerol, i.e. compounds which can be covalently 
incorporated in the polyurethane. 
Particularly suitable surfactants are those which contain several of these 
functional groups in the molecule, such as for example ethoxylated castor 
oil containing 20 to 400% by weight and preferably 40 to 200% by weight of 
EO, based on non-ethoxylated castor oil, or epoxidized soybean oil 
ring-opened with alcohols or carboxylic acids which, after ring opening, 
is reacted with alkylene oxides, preferably ethylene oxide, to a content 
of 20 to 400% by weight and preferably 40 to 200% by weight of alkylene 
oxide, based on the non-alkoxylated starting product. 
A surfactant produced as described in German application DE-A1 39 23 394 
from epoxidized soybean oil ring-opened with fatty acid by subsequent 
reaction with ethylene oxide to an ethylene oxide content of 20 to 400% by 
weight and preferably 40 to 200% by weight, based on the non-ethoxylated 
starting product, is most particularly suitable. 
The hydroxyl values of the surfactants according to the invention are in 
the range from 10 to 200 and preferably in the range from 30 to 100. 
The compounds mentioned are used in quantities of 10 to 80% by weight and 
preferably in quantities of 20 to 50% by weight, based on the polyol, for 
the replacement. 
Another advantage of the last of the above-mentioned surfactants according 
to the invention is that, surprisingly, they do not crystallize at room 
temperature despite their high ethylene oxide content. Accordingly, no 
unwanted precipitations occur in the reaction products produced from them 
with diisocyanates, even at low temperatures. 
The other components of the polyurethane foams will now be described. 
Polyols 
The polyols used are typical polyethers or polyesters which are described, 
for example, in Ullmanns Enzyklopadie der technischen Chemie, 4th Edition, 
Vol. 19, pages 304 to 305, Verlag Chemie, Weinheim. In addition, 
oleochemical polyols obtainable by reaction of epoxidized triglycerides 
with alcohols and, optionally, subsequent transesterification of the 
reaction products on their own or with more added non-epoxidized 
triglyceride, are preferably used. Oleochemical polyols from the 
transesterification of polyfunctional polyols, such as the adduct of 
glycerol with ethylene oxide or polymerized glycerol with triglycerides, 
for example rapeseed oil, may also be used. Castor oil is another suitable 
oleochemical polyol. The polyols have OH values of 50 to 400 and 
preferably 100 to 300. 
Isocyanates 
Suitable difunctional or polyfunctional isocyanates are any of the products 
known to the expert which are typically used in polyurethane chemistry and 
which are described, for example, in Ullmanns Enzyklopadie der technischen 
Chemie, 4th Edition, Vol. 19, pages 303 to 304, Verlag Chemie, Weinheim. 
Aromatic difunctional or polyfunctional isocyanates are preferably used, 
diphenyl methane diisocyanate and/or the technical qualitities of these 
diisocyanates containing molecules of high functionality being 
particularly preferred. 
Auxiliaries 
The blowing agents used are preferably HCFC's, such as 
difluorochloromethane, difluorochloroethane, dichlorofluoroethane or 
tetrafluoroethane, or CFC-free blowing agents, such as dimethyl ether, 
propane or isobutane. However, CFC-containing blowing agents may also be 
used for the purposes of the invention although they are not preferred. 
The polyurethane foams may contain other compounds, such as flameproofing 
agents, for example the tris-(chloroalkyl)-phosphates or aryl phosphates 
known from the prior art. The quantity in which the flameproofing agents 
are used is in the range from 8 to 15% by weight, based on the mixture as 
a whole. Suitable catalysts for accelerating the reaction are, for 
example, the tertiary amines known to the expert, for example 
2,2'-dimorpholinodiethyl ether. Silicone oils, optionally even modified 
silicone oils, may be used as stabilizers. 
Production and Application 
The polyurethane compositions according to the invention are produced by 
mixing the polyols with the modifying nonionic hydrophilic surfactant, the 
difunctional or polyfunctional isocyanate, the blowing agent, the 
flameproofing agent, the catalyst and optionally the stabilizer and 
packing the resulting mixture in a pressurized container equipped with a 
spray valve. 
When the pressurized mixture issues from the valve, a polyurethane foam is 
formed in the usual way and may be used, for example, for filling joints 
with foam, for insulation and the like. 
COMMERCIAL APPLICATIONS 
The polyurethane compositions according to the invention may be used above 
all in the building industry for the production of fine-cell, homogeneous, 
void-free or substantially void-free polyurethane foams on dry substrates 
without any need to moisten the foams. 
The polyurethane compositions packed in pressurized containers are stable 
against precipitation during storage at low temperatures.

EXAMPLES 
All quantities are expressed as percentages by weight, unless otherwise 
indicated. 
General procedure: 
A polyurethane composition was prepared from the following ingredients: 
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19.7 pbw of an oleochemical polyol prepared by ring 
opening of epoxidized soybean oil with methanol 
and subsequent partial transesterification, 
OHV = 180 
34.3 pbw of Desmodur .RTM. VKS, 31% NCO content 
24 pbw of trichloropropyl phosphate 
19.6 pbw of a blowing agent of C.sub.2 H.sub.3 CIF.sub.2 + CHCIF.sub.2 
1.6 pbw of Dabco .RTM. DC 190 
0.8 pbw of dimorpholinodiethyl ether 
100 pbw of polyurethane composition 
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DABCO DC 190 is a silicone surfactant manufactured by Dow Corning. Desmodur 
VKS is a polymeric isocyanate manufactured by Bayer AG. 
The following nonionic hydrophilic surfactants were used: 
Surfactant 1: ethoxylated castor oil containing 65% by weight of ethylene 
oxide 
Surfactant 2: epoxidized soybean oil ring-opened with a mixture of 
C.sub.6-12 fatty acids and subsequently reacted with ethylene oxide to an 
ethylene oxide content of 150% by weight, OH value=54.7. 
Performance test: 
The one-component polyurethane mixture was sprayed from pressurized 
containers into 40 mm wide and 400 mm long joints. Dry cellulose and 
cellulose soaked with water were used as the substrates. The quality of 
the foams was evaluated after curing. The polyurethane strands were then 
cut up in order to reveal any voids. 
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Moist substrate: 
Example No. 
1 (Comp.) 2 3 
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Basic polyol 
100% 70% 70% 
Surfactant 1 
-- 30% -- 
Surfactant 2 
-- -- 30% 
Foam volume 
Good Good Very good 
Foam structure 
Inhomogeneous 
Partly inhomo- 
Homogen- 
geneous eous 
Void formation 
Slight Slight Very slight 
Dimensional 
6% By volume 
3% By volume 
1% By volume 
stability 
(shrinkage) 
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Dry substrate 
Example No. 
4 (Comp.) 5 6 
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Basic polyol 
100% 70% 70% 
Surfactant 1 
-- 30% -- 
Surfactant 2 
-- -- 30% 
Foam volume 
Poor Good Very good 
Foam structure 
Very inhomoge- 
Partly inhomo- 
Homogen- 
neous geneous eous 
Void formation 
Frequent Slight Very slight 
Dimensional 
10% By volume 
3% By volume 
1% By volume 
stability 
(shrinkage) 
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