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Description  |
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The present invention relates to a process for the production of plastic
foams, preferably rigid foams containing urethane groups or urethane and
isocyanurate groups, by reacting the starting components (a), (b) and, if
desired, (c), where the blowing agent employed is at least one
vinylfluoroalkane of the formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which n is an integer from 1 to 6, (di), or a mixture comprising at
least one such vinylfluoroalkane (di) and at least one further physical
and/or chemical blowing agent (dii) which is different from (di), and to
blowing agent-containing emulsions which contain at least one
vinylfluoroalkane (di) or a mixture of (di) with at least one other
blowing agent (dii) and at least one of the starting components (a), (b)
or (c) or (b) and (c), and to plastic foams containing said
vinylfluoroalkane as insulating gases.
Chlorofluorocarbons (CFCs) such as fluorotrichloromethane (CFC 11),
dichlorodifluoromethane (CFC 12) and 1,1,2-trichloro-1,2,2-trifluoroethane
(CFC 113) are at present the blowing agents and insulating gases most
widely employed for the manufacture of all kinds of plastic foams intended
for insulation, in particular closed-cell foams, especially polyurethane
or polyisocyanurate foams, extruded polystyrene and polyethylene foams,
phenolic foams, poly(vinyl chloride) foams, etc.
CFCs 11 and 12 are also employed for the manufacture of polyolefin foams
such as polyethylene and polypropylene, polystyrene or poly(vinyl
chloride), more especially intended for packaging.
However, CFCs 11, 12 and 113 are included amongst fully halogenated
chlorofluorocarbons which, because of their high chemical stability, are
suspected of attacking or degrading stratospheric ozone and whose use is
envisaged to be prohibited at the end of this century.
As a solution to this problem it is currently envisaged to replace the CFCs
by chlorofluorohydrocarbons containing at least one hydrogen atom, such as
chlorodifluoromethane (HCFC 22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC
123), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC 124),
1,1-dichloro-1-fluoroethane (HCFC 241b) and 1-chloro-1,1-difluoroethane
(HCFC 142b). Although the HCFCs exhibit ozone-depletion potentials
(O.D.P.) which are markedly lower than those of the CFCs, their O.D.P. is
nevertheless not zero and their substitution for the CFCs can therefore
represent only a temporary solution.
There is therefore still a need for compounds which have no destructive
effect on stratospheric ozone (O.D.P.=0) and exhibit properties which are
similar to those of CFCs 11, 12 and 113, in order to replace the latter as
blowing agents and insulating gases in the manufacture of plastic foams.
It has now been found that this problem can be solved by employing
vinylfluoroalkane of formula:
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which C.sub.n F.sub.2n+1 denotes a linear or branched perfluoroalkyl
radical and n is an integer from 1 to 6. These compounds have ODP of zero;
the properties of the preferred compounds are illustrated by the following
table.
______________________________________
C.sub.n F.sub.2n+1
PROPERTIES (CF.sub.3).sub.2 CF
C.sub.4 F.sub.9
C.sub.5 F.sub.13
______________________________________
Boiling point (.degree.C.)
31 59 105
Vapour thermal conduc-
9.2 8.1 5.7
tivity at 10.degree. C. (mW/m K)
Vapour pressure at 10.degree. C.
445 137 143
(mbar)
______________________________________
The present invention therefore relates to the use of at least one of said
vinylfluoroalkanes as blowing agent and insulating gas in the production
of plastic foams.
The vinylfluoroalkane of formula CH.sub.2 50 CH--C.sub.n F.sub.2n+1 can be
obtained industrially by processes which are known per se, for example by
a two-stage process consisting successively in:
the addition of ethylene to the corresponding perfluoroalkyl iodide C.sub.n
f.sub.2n+1 in the presence of a catalyst based on copper and ethanolamine,
and
the dehydroiodination of the iodide C.sub.n F.sub.2n+1 --CH.sub.2 CH.sub.2
I thus obtained, in the presence of alcoholic potassium hydroxide.
The blowing agent most widely employed at present for the manufacture of
polystyrene and poly(vinyl chloride) foams is CFC 12. This compound is
preferably replaced here by a vinylfluoroalkane whose perfluoroalkyl
radical C.sub.n F.sub.2n+1 contains from 1 to 3 carbon atoms, for example
vinylperfluoroisopropane.
The main blowing agents currently employed for the production of polyolefin
foams (polyethylene, polypropylene) are CFCs 11 and 12, employed by
themselves or mixed with 1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC 114)
or with hydrocarbons. CFC 11 is preferably replaced here by a
vinylfluoroalkane in which the radical C.sub.n F.sub.2n+1 contains from 3
to 6 carbon atoms, for example vinyl-perfluoro-n-butane, and CFC 12 is
preferably replaced by a vinylfluoroalkane in which this radical C.sub.n
F.sub.2n+1 contains from 1 to 3 carbon atoms, for example
vinyl-fluoroisopropane. In this application the vinylfluoroalkanes
according to the invention can be employed by themselves, mixed with each
other or mixed with alkanes (for example butane); the proportion by weight
of the secondary blowing agent in such a mixture may range up to 90%.
The main blowing agents currently employed for the production of phenolic
foams are CFCs 11 and 113, employed by themselves or mixed. CFCs 11 and
113 are preferably replaced here by vinylfluoroalkane in which the radical
C.sub.n F.sub.2n+1 contains from 3 to 6 carbon atoms, for example
vinylperfluoro-n-hexane. In this application the vinylperfluoroalkanes
according to the invention can be employed by themselves, mixed with each
other or mixed with alkanes, which may be halogenated, for example
pentane, butane, perfluoropentane or 1,1-dichloro-1-fluoroethane; the
proportion of alkane, which may be halogenated in such a mixture may range
up to 90% by weight.
The processes for the production of polystyrene or PVC foams, polyolefin
foams and phenolic foams are well known and do not need to be described
here, since it suffices to replace the usual blowing agent (CFC 11, 12 or
113) with a compound of formula (I) or a mixture of such compounds. The
molar quantity of compound(s) of formula (I) to be used is substantially
the same as that of the blowing agent which they (it) replace(s).
The production of foams containing urethane groups (abbreviated to PU foams
below) with a very wide variety of mechanical properties by reacting
relatively high-molecular-weight polyhydroxyl compounds and, if desired,
low-molecular-weight chain extenders or cross-linking agents with organic
polyisocyanates in the presence of catalysts, blowing agents and, if
desired, assistants and/or additives is known and is described in numerous
patents and other publications. An appropriate choice of the starting
components allows soft and elastic, semirigid or rigid PU foams to be
produced by this process.
Neither is the production of foams containing bonded urethane and
isocyanurate groups new. In this process, organic polyisocyanates are
partially cyclized and polymerized in the presence of catalysts, and the
resultant polyisocyanates containing isocyanurate groups (PIR) are then
reacted with polyhydroxyl compounds in the presence of PU catalysts and
blowing agents. In another procedure, the organic polyisocyanates are
simultaneously partially cyclized in the presence of substoichiometric
amounts of polyhydroxyl compounds, catalysts with various actions and
blowing agents, and the polyhydroxyl compounds are added onto the
resultant unmodified polyisocyanates containing isocyanurate groups.
A review on the production of rigid PU foams and PU-PIR foams is published,
for example, in the monograph by J. H. Saunders and K. C. Frisch, High
Polymers, Volume XVI, Polyurethanes, Parts 1 and 2, Interscience
Publishers, 1962 and 1964 respectively, and the Kunststoff-Handbuch,
Volume VII, Polyurethane, Carl-Hanser-Verlag, Munich, 1st edition, 1966,
and 2nd edition, 1983.
Also known is the use of rigid PU or PU-PIR foams of this type for the
production of composite or sandwich elements, which are usually built up
from a rigid foam and at least one, preferably two, outer layers
comprising a rigid or elastic material, e.g. paper, plastic films, metal
sheeting, glass nonwoven, chipboard, inter alia, and the foam-filling of
cavities in domestic appliances, such as cooling equipment, for example
refrigerators or chest freezers, or hot-water storage tanks, with rigid
foams of this type as thermal insulators.
Blowing agents used worldwide on a large scale for the production of heat-
and cold-insulating rigid PU or PU-PIR foams are chlorofluoroalkanes,
preferably trichlorofluoromethane. The only disadvantage of these blowing
gases is environmental pollution, since they are suspected of
participating in the depletion of the ozone layer in the stratosphere.
In order to reduce the amount of chlorofluoroalkanes, the blowing gas used
is predominantly water, which reacts with the polyisocyanate to form
carbon dioxide, which acts as the actual blowing agent. Rigid PU foam
formulations of this type have the disadvantage of a high consumption of
polyisocyanate merely for the reaction of the water to form the carbon
dioxide. A further disadvantage is an impairment in the heat-insulation
properties due to the relatively high thermal conductivity of the carbon
dioxide compared with chlorofluoroalkanes.
According to EP-A-351 614, the blowing agents used may furthermore be
fluorinated hydrocarbons, perfluorinated hydrocarbons, sulfur hexafluoride
or mixtures of at least two of these compounds. Since these fluorinated or
perfluorinated blowing agents are only sparingly soluble or insoluble in
the starting components for the production of the polyisocyanate
polyaddition products, they are emulsified in at least one organic and/or
modified organic polyisocyanate, in at least one relatively
high-molecular-weight compound containing at least two reactive hydrogen
atoms or in a mixture of at least one relatively high-molecular-weight
compound containing at least two reactive hydrogen atoms and a
low-molecular-weight chain extender and/or crosslinking agent. This method
allows cellular plastics having a uniform and fine cell structure to be
produced, but has the disadvantage of the narrow choice of suitable
fluorinated or perfluorinated compounds having a boiling point in the
required boiling point range, and the high price of these blowing agents.
In order to obtain cellular plastics having the technically desired cell
structure, the choice is restricted to mixtures of perfluoropentane and
perfluorohexane. A further disadvantage is that blowing agents of this
type are relatively resistant chemically, are degraded only slowly in the
atmosphere and can therefore contribute to global warming.
Low-boiling hydrocarbons which can be used as blowing agents are soluble in
the starting components for the production of the polyisocyanate
polyaddition products and give foams having a very coarse, frequently
nonuniform cell structure and increased thermal conductivity.
The mechanism of foam formation in the production of polyisocyanate
polyaddition products and the effect of surface-active assistants based on
siloxane-oxyalkylene copolymers on this reaction has been described by B.
Kanner et al. (J. of Cellular Plastics, Jan. 1969, pages 32 to 39).
It is an object of the present invention to replace all or at least some of
the chlorofluorocarbons known as blowing agents for the production of
rigid PU or PU-PIR foams by other, environmentally friendly blowing agents
without adversely affecting the fine-celled foam structure, as can be
achieved using emulsions based on fluorinated hydrocarbons.
We have found that, surprisingly, this object is achieved by using
fluorinated olefins as the blowing agent.
The present invention accordingly provides a process for the production of
plastic foams, which comprises using at least one vinylfluoroalkane of the
formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which --C.sub.n F.sub.2n+1 is linear or branched perfluoroalkyl and n is
an integer from 1 to 6, as blowing agent and/or insulating gas, with the
proviso that, if the vinylfluoroalkane is vinylperfluoro-n-butane, it is
not employed in admixture with dichloroethylene or in admixture with more
than 90% of 1,1-dichloro-1-fluoroethane.
The present invention preferably provides a process for the production of
rigid foams containing urethane groups or urethane and isocyanurate
groups, by reacting
a) an organic and/or modified organic polyisocyanate with
b) at least one relatively high-molecular-weight compound containing at
least two reactive hydrogen atoms, and, if desired,
c) a low-molecular-weight chain extender and/or cross
linking agent,
in the presence of
d) a blowing agent,
e) a catalyst and, if desired,
f) assistants and/or additives,
wherein the blowing agent (d) used is at least one vinylfluoroalkane of the
formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which n is an integer from 1 to 6, with the proviso that, if the
vinylfluoroalkane is vinylperfluoro-n-butane, it is not employed in
admixture with dichloroethylene or in admixture with more than 90% of
1,1-dichloro-1-fluoroethane.
The present invention furthermore provides blowing agent-containing
emulsions which contain at least one vinylfluoroalkane of the formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which n is an integer from 1 to 6, (di), and at least one organic and/or
modified organic polyisocyanate (a) or at least one relatively
high-molecular-weight compound containing at least two reactive hydrogen
atoms (b), or at least one low-molecular-weight chain extender and/or
crosslinking agent (c), or a mixture of (b) and (c).
Since the vinylfluoroalkanes (di) which can be used according to the
invention are only sparingly soluble or essentially insoluble, in the
necessary amounts, in the starting components (a), (b) and, if used, (c)
or in mixtures of at least two of these starting components, they are
expediently emulsified in at least one of the starting components, for
example in (a), (b) or (c), or in a mixture of (b) and (c) or (a) and in a
mixture of (b) and (c), and used in the form of emulsions for the
production of the rigid foams.
In contrast to highly fluorinated or perfluorinated, low-boiling alkanes,
the vinylfluoroalkanes of the formula CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
which can be used according to the invention react very readily with
hydroxyl free radicals and are therefore degraded in the lower atmosphere.
It is furthermore advantageous that the vinylfluoroalkane-containing
emulsions and the reaction mixtures formed therefrom flow very readily.
The molds, in particular those having spatial shapes which are difficult
to fill, can be filled more rapidly and more uniformly, so that moldings
of homogeneous cell structure and low densities can be produced without
difficulties. The rigid PU or PU-PIR foams produced by the process
according to the invention in open or closed molds are fine-celled and
have low thermal conductivity.
The rigid PU or PU-PIR foams are prepared by the process according to the
invention using, with the exception of blowing agent (d), the starting
components which are known per se, to which the following details apply.
Suitable organic polyisocyanates (a) are conventional aliphatic,
cycloaliphatic, araliphatic and preferably aromatic polyisocyanates.
The following may be mentioned as examples: alkylene diisocyanates having
from 4 to 12 carbon atoms in the alkylene moiety, such as 1,12-dodecane
diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate,
2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate
and preferably hexamethylene 1,6-diisocyanate; cycloaliphatic
diisocyanates, such as cyclohexane 1,3- and 1,4-diisocyanate and any
desired mixtures of these isomers,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone
diisocyanate), 2,4-and 2,6-hexahydrotolylene diisocyanate and the
corresponding isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane
diisocyanate and the corresponding isomer mixtures, and preferably
aromatic diisocyanates and polyisocyanates, e.g. 2,4- and 2,6-tolylene
diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'- and
2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures,
mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates,
polyphenyl-polymethylene polyisocyanates, mixtures of 4,4'-, 2,4'- and
2,2'-diphenylmethane diisocyanates and polyphenyl-polymethylene
polyisocyanates (crude MDI), and mixtures of crude MDI and tolylene
diisocyanates. The organic diisocyanates and polyisocyanates may be
employed individually or in the form of mixtures.
Frequently, modified polyisocyanates are also used, i.e. products which are
obtained by partial chemical reaction of organic diisocyanates and/or
polyisocyanates. Specific examples are ester-, urea-, biuret-,
allophanate-, carbodiimide-, isocyanurate- and/or urethane-containing
diisocyanates and/or polyisocyanates. Individual examples are
urethane-containing organic, preferably aromatic, polyisocyanates
containing from 33.6 to 15% by weight, preferably from 31 to 21% by
weight, of NCO, based on the total weight, for example
4,4'-diphenylmethane diisocyanate, or 2,4- or 2,6-tolylene diisocyanate
modified by means of low-molecular-weight diols, triols, dialkylene
glycols, trialkylene glycols or polyoxyalkylene glycols having molecular
weights of up to 1500, specific examples of di- and polyoxyalkylene
glycols, which can be employed individually or as mixtures, being
diethylene glycol, dipropylene glycol, polyoxyethylene glycol or triol,
polyoxypropylene glycol or triol and polyoxypropylene-polyoxyethylene
glycol or triol. NCO-containing prepolymers containing from 25 to 9% by
weight, preferably from 21 to 14% by weight, of NCO, based on the total
weight, and prepared from the polyester- and/or preferably
polyether-polyols described below and 4,4'-diphenylmethane diisocyanate,
mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, 2,4- and/or
2,6-tolylene diisocyanates or crude MDI are also suitable. Furthermore,
liquid polyisocyanates containing carbodiimide groups and/or isocyanu-rate
rings and containing from 33.6 to 15% by weight, preferably from 31 to 21%
by weight, of NCO, based on the total weight, e.g. based on 4,4'-, 2,4' -
and/or 2,2'-diphenylmethane diisocyanate and/or 2,4- and/or 2,6-tolylene
diisocyanate, have also proven successful.
The modified polyisocyanates, if desired, may be mixed with one another or
with unmodified organic polyisocyanates, e.g. 2,4'- or
4,4'-diphenylmethane diisocyanate, crude MDI or 2,4- and/or 2,6-tolylene
diisocyanate.
Organic polyisocyanates which have proven particularly successful and are
therefore preferred for use for the production of rigid PU foams are
mixtures of tolylene diisocyanates and crude MDI or mixtures of modified
urethane-containing organic polyisocyanates containing from 33.6 to 15% by
weight of NCO, in particular based on tolylene diisocyanates,
4,4'-diphenylmethane diisocyanate, diphenylmethane diisocyanate isomer
mixtures or crude MDI, in particular crude MDI having a diphenylmethane
diisocyanate isomer content of from 30 to 80% by weight, preferably from
30 to 55% by weight.
The relatively high-molecular-weight compound (b) containing at least two
reactive hydrogen atoms is preferably a polyhydroxyl compound having a
functionality of from 2 to 8, preferably from 3 to 8, and a hydroxyl
number of from 150 to 850, preferably from 200 to 600.
Examples which may be mentioned are polythioether-polyols,
polyester-amides, hydroxyl-containing polyacetals and hydroxyl-containing
aliphatic polycarbonates and preferably polyester-polyols and
polyetherpolyols. Also used are mixtures of at least two of the said
polyhydroxyl compounds, so long as they have a mean hydroxyl number within
the abovementioned range.
Suitable polyester-polyols may 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, maleic acid, fumaric acid, phthalic
acid, isophthalic acid and terephthalic acid. The dicarboxylic acids may
be used either individually or mixed with one another. The free
dicarboxylic acids may also be replaced by the corresponding dicarboxylic
acid derivatives, for example dicarboxylic acid mono- or diesters of
alcohols having from 1 to 4 carbon atoms or dicarboxylic anhydrides.
Preference is given to dicarboxylic acid mixtures comprising succinic
acid, glutaric acid and adipic acid in ratios of, for example, from 20 to
35 : 35 to 50 : 20 to 32 parts by weight, and in particular adipic acid.
Examples of dihydric and polyhydric alcohols, in particular diols, are
ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene
glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10decanediol,
glycerol and trimethylolpropane. Preference is given to ethanediol,
diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and
mixtures of at least two of said diols, in particular mixtures of
1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol. Furthermore,
polyester-polyols made from lactones, e.g. .epsilon.-caprolactone, or
hydroxycarboxylic acids, e.g. .omega.-hydroxycaproic acid, may also be
employed.
The polyester-polyols may be prepared by polycondensing the organic, e.g.
aromatic and preferably aliphatic polycarboxylic acids and/or derivatives
thereof and polyhydric alcohols without using a catalyst or preferably in
the presence of an esterification catalyst, expediently in an inert gas
atmosphere, e.g. nitrogen, carbon dioxide, helium, argon, inter alia, in
the melt at from 150.degree. to 250.degree. C., preferably from
180.degree. to 220.degree. C., at atmospheric pressure or under reduced
pressure until the desired acid number, which is advantageously less than
10, preferably less than 2, is reached. In a preferred embodiment, the
esterification mixture is polycondensed at the abovementioned temperatures
under atmospheric pressure and subsequently under a pressure of less than
500 mbar, preferably from 50 to 150 mbar, until an acid number of from 80
to 30, preferably from 40 to 30, has been reached. Examples of suitable
esterification catalysts are iron, cadmium, cobalt, lead, zinc, antimony,
magnesium, titanium and tin catalysts in the form of metals, metal oxides
or metal salts. However, the polycondensation may also be carried out in
the liquid phase in the presence of diluents and/or entrainers, e.g.
benzene, toluene, xylene or chlorobenzene, for removal of the water of
condensation by azeotropic distillation.
The polyester-polyols are advantageously prepared by polycondensing the
organic polycarboxylic acids and/or derivatives thereof with polyhydric
alcohols in a molar ratio of from 1:1 to 1.8, preferably from 1:1.05 to
1.2.
The polyester-polyols obtained preferably have a functionality of from 2 to
3, and a hydroxyl number of from 150 to 400, in particular from 200 to
300.
However, the preferred polyhydroxyl compounds are polyether-polyols
prepared by conventional processes, for example by anionic polymerization
using 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
using at least one initiator molecule containing from 2 to 8, preferably
from 3 to 8, bonded reactive hydrogen atoms, or by cationic polymerization
using Lewis acids, such as antimony pentachloride, boron fluoride
etherate, inter alia, or bleaching earth as catalysts, from one or more
alkylene oxides having from 2 to 4 carbon atoms in the alkylene moiety.
Examples of suitable alkylene oxides are tetrahydrofuran, 1,3-propylene
oxide, 1,2- and 2,3-butylene oxide, styrene oxide and preferably ethylene
oxide and 1,2-propylene oxide. The alkylene oxides may be used
individually, alternately one after the other or as 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, unsubstituted or N-mono-, N,N-and
N,N'-dialkyl-substituted diamines having from 1 to 4 carbon atoms in the
alkyl moiety, such as unsubstituted or mono- or dialkyl-substituted
ethylenediamine, diethylenetriamine,
triethylenetetramine,1,3-propylenediamine, 1,3- and 1,4-butylenediamine,
1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamines,
2,3-, 2,4-and 2,6-tolylenediamine and 4,4'-, 2,4'- and
2,2'-diaminodiphenylmethane.
Other suitable initiator molecules are alkanolamines, e.g. ethanolamine,
diethanolamine, N-methyl- and N-ethyl-ethanolamine, N-methyl- and
N-ethyl-diethanolamine, and triethanolamine, and ammonia. Preference is
given to polyhydric alcohols, e.g. dihydric or in particular trihydric
and/or polyhydric alcohols, such as ethanediol, 1,2- and 1,3-propanediol,
diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol,
glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose.
The polyether-polyols preferably have a functionality of from 3 to 8, in
particular from 3 to 6, and hydroxyl numbers of from 200 to 850, in
particular from 300 to 600.
Other suitable polyether-polyols are the melamine/polyether-polyol
dispersions of EP-A-23 987 (U.S. Pat. No. 4,293,657), the
polymer/polyether-polyol dispersions prepared from polyepoxides and epoxy
resin curing agents in the presence of polyether-polyols in accordance
with DE-A-29 43 689 (U.S. Pat. No. 4,305,861), the dispersions of aromatic
polyesters in polyhydroxyl compounds of EP-A-62 204 (U.S. Pat. No.
4,435,537) or DE-A-33 00 474, the dispersions of organic and/or inorganic
fillers in polyhydroxyl compounds of EP-A-11 751 (U.S. Pat. No.
4,243,755), the polyurea/polyether-polyol dispersions of DE-A-31 25 402,
the tris(hydroxyalkyl) isocyanurate/polyether-polyol dispersions of
EP-A-136 571 (U.S. Pat. No. 4,514,526) and the crystallite suspensions of
DE-A-33 42 176 and DE-A-33 42 177 (U.S. Pat. No. 4,560,708); the
information given in said patents should be regarded as part of the
description of the present application.
Like the polyester-polyols, the polyether-polyols can be used individually
or in the form of mixtures. Furthermore, they may be mixed with the
abovementioned dispersions, suspensions or polyester-polyols and the
hydroxyl-containing polyester-amides, polyacetals and/or polycarbonates.
Examples of suitable hydroxyl-containing polyacetals are the compounds
which can be prepared from glycols, such as diethylene glycol, triethylene
glycol, 4,4'-dihydroxyethoxydiphenyldimethylmethane, hexanediol and
formaldehyde. Suitable polyacetals can also be prepared by polymerizing
cyclic acetals.
Suitable hydroxyl-containing polycarbonates are those of a conventional
type, 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 glycol, with diaryl carbonates, e.g.
diphenyl carbonate, or phosgene.
The polyester-amides include, for example, the predominantly linear
condensates obtained from polybasic, saturated and/or unsaturated
carboxylic acids or anhydrides thereof and amino alcohols, or mixtures of
polyhydric alcohols and amino alcohols and/or polyamines.
Polyhydroxyl compounds which have proven particularly successful and are
therefore preferred are mixtures expediently containing, based on 100
parts by weight,
bi) from 0 to 95 parts by weight, preferably from 20 to 80 parts by weight,
of a sucrose-initiated polyether-polyol having a hydroxyl number of from
300 to 500, preferably from 350 to 450, based on 1,2-propylene oxide or
1,2-propylene oxide and ethylene oxide,
bii) from 0 to 15 parts by weight, preferably from 5 to 15 parts by weight,
of a sorbitol-initiated polyether-polyol having a hydroxyl number of from
400 to 600, preferably from 450 to 550, based on 1,2-propylene oxide or
1,2-propylene oxide and ethylene oxide,
biii) from 0 to 20 parts by weight, preferably from 5 to 15 parts by
weight, of an ethylenediamine-initiated polyether-polyol having a hydroxyl
number of from 700 to 850, preferably from 750 to 800, based on
1,2-propylene oxide, and
biiii) from 0 to 60 parts by weight, preferably from 5 to 40 parts by
weight, of a polyether-polyol having a hydroxyl number of from 400 to 600,
preferably from 450 to 550, based on 1,2-propylene oxide or 1,2-propylene
oxide and ethylene oxide and prepared using a mixture of sucrose and
triethanolamine in a weight ratio of from 1:2 to 2:1 as initiator
molecules.
The rigid PU or PU-PIR foams may be prepared with or without the use of
chain extenders and/or crosslinking agents (c). However, it may prove
advantageous, in order to modify the mechanical properties, to add chain
extenders, crosslinking agents or, if desired, mixtures thereof. The chain
extenders and/or crosslinking agents used are preferably alkanolamines, in
particular diols and/or triols, having a molecular weight of less than
400, preferably from 60 to 300. Examples are alkanolamines, e.g.
trialkanolamines such as triethanolamine, triisopropanolamine and products
of the addition reaction of ethylene oxide or 1,2-propylene oxide and
alkylenediamines having from 2 to 6 carbon atoms in the alkylene moiety,
e.g. N,N,N',N'-tetra(2-hydroxyethyl)-ethylenediamine and
N,N,N',N'-tetra(2-hydroxypropyl)-ethylenediamine, aliphatic,
cycloaliphatic and/or araliphatic diols having from 2 to 14 carbon atoms,
preferably from 4 to 10 carbon atoms, e.g. ethylene glycol,
1,3-propanediol, 1,10-decanediol, o-, m- and 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-
and 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 aromatic diamines, e.g.
tolylenediamines and/or diaminodiphenylmethanes, and the abovementioned
alkanolamines, diols and/or triols as initiator molecules.
The amount of chain extender, crosslinking agent or mixture thereof used,
if any, for the production of the rigid PU or PU-PIR foams is expediently
from 0 to 20% by weight, preferably from 2 to 8% by weight, based on the
weight of the polyhydroxyl compound.
The blowing agent (d) used for the production of the rigid PU or PU-PIR
foam is according to the invention a vinylfluoroalkane of the formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which n is an integer from 1 to 6, preferably from 3 to 5, in particular
3 or 4. Specific examples of suitable vinylfluoroalkanes are
vinylperfluoromethane, vinylperfluoroethane, vinylperfluoro-n- or
-isopropane, vinylperfluorobutane, vinylperfluoro-sec.-butane,
vinylperfluoropentane and vinylperfluorohexane. The vinylfluoralkane (di)
can be used alone or in a mixture.
Also suitable are mixtures of the appropriate vinylperfluoro-n- and
-isoalkanes or technical-grade mixtures thereof. Blowing agents (d) which
have proven particularly successful, and ones which are therefore
preferred, are vinylperfluoroisopropane and vinylperfluorobutane.
Since the vinylfluoroalkane (di) which can be used according to the
invention is, as stated above, only sparingly soluble or essentially
insoluble, in the necessary amounts, in starting components (a), (b) and
(c) or in a mixture of at least two of these starting components, it is
preferably emulsified in one of the starting components (a), (b) and, if
used, (c) or in a mixture of at least two of these. The vinylfluoroalkane
or the mixture of vinylfluoroalkanes is usually used in an amount of from
1 to 40 parts by weight, preferably from 1 to 15 parts by weight, in
particular from 2 to 10 parts by weight, based on 100 parts by weight of
the starting components (a) and (b) or (a) to (c).
The vinylfluoroalkane (di) may be employed as the only blowing agent.
However, the vinylfluoroalkane (di) or vinylfluoroalkane emulsion which
can be used according to the invention can also be used in combination
with other, physical, inert blowing agents or chemical blowing agents
(dii) which are different from (di), or in combination with a mixture of
physical and chemical blowing agents which are different from (di).
A suitable blowing agent mixture (d) for the production of the rigid foams
containing urethane groups or urethane and isocyanurate groups by the
process according to the invention can thus preferably contain or comprise
di) at least one vinylfluoroalkane of the formula
CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1
in which n is an integer from 1 to 6, in particular 3 or 4, or a mixture
thereof, and
dii) at least one further physical blowing agent which is different from
(di) or a chemical blowing agent, or a mixture of such physical and
chemical blowing agents.
Examples of suitable physical blowing agents are:
alkanes having 4 to 12 carbon atoms, preferably 5 to 8 carbon atoms,
cycloalkanes having 4 to 6 carbon atoms, preferably 5 or 6 carbon atoms,
linear or cyclic, saturated or olefinically unsaturated ethers having 2 to
5 carbon atoms,
aliphatic carboxylic acid esters having a maximum boiling point of
142.degree. C., preferably below 80.degree. C., aliphatic and/or
cycloaliphatic ketones having 3 to 5 carbon atoms,
partially halogenated chlorofluorocarbons having 1 or 2 carbon atoms,
partially fluorinated or preferably perfluorinated tertiary alkylamines
having 3 to 9 carbon atoms, preferably 4 to 6 carbon atoms,
partially fluorinated or perfluorinated, linear or cyclic ethers having 2
to 12 carbon atoms, preferably 3 to 6 carbon atoms, and
preferably fluorinated or perfluorinated, advantageously aliphatic or
cycloaliphatic hydrocarbons having 3 to 8 carbon atoms, preference being
given to aliphatic or cycloaliphatic, fluorinated hydrocarbons having 4 to
6 carbon atoms which are liquid at room temperature and contain at least
one bonded hydrogen atom, and aliphatic or cycloaliphatic, perfluorinated
hydrocarbons having 4 to 7 carbon atoms.
Specific examples of physical blowing agents (dii) of the said type are
gaseous or preferably liquid, linear or branched alkanes, e.g. butane, n-
and isopentane and technical-grade pentane mixtures, n- and isohexanes, n-
and isoheptanes, n- and isooctanes, n- and isononanes, n- and isodecanes,
n- and isoundecanes and n- and isododecanes. Since very good results with
respect to the stability of the emulsions, the processing properties of
the reaction mixture and the mechanical properties of the rigid foams
containing urethane groups or urethane and isocyanurate groups are
achieved when n-pentane, isopentane, n-hexane, or isohexane or a mixture
thereof, is used, these alkanes are preferably employed. Furthermore,
specific examples of cycloalkanes are cyclobutane, preferably
cyclopentane, cyclohexane or mixtures thereof, specific examples of linear
or cyclic ethers are dimethyl ether, diethyl ether, methyl ethyl ether,
vinyl methyl ether, vinyl ethyl ether, divinyl ether, tetrahydrofuran and
furan, specific examples of aliphatic carboxylic acid esters are methyl,
ethyl, n-propyl, isopropyl and butyl acetate and preferably methyl and
ethyl formate, specific examples of ketones are acetone, methyl ethyl
ketone and cyclopentanone, specific examples of partially halogenated
chlorofluorocarbons are difluoromonochloromethane (R 22),
1,1,1-trifluoro-2,2-dichloroethane (R 123) and
1,1,1-dichloromonofluoroethane (R 141b), specific examples of fluorinated
or perfluorinated, tertiary alkylamines are perfluorodimethylethylamine,
perfluorodiethylmethylamine, perfluorotrimethylamine,
perfluorotriethylamine, perfluorodimethyl-n-propylamine,
perfluorodiethyl-n-propylamine and preferably
perfluorodimethylisopropylamine and the corresponding partially
fluorinated tertiary alkylamines, specific examples of partially
fluorinated or perfluorinated, linear or cyclic ethers are
2,2,2-trifluoroethyl methyl ether (CF.sub.3 CH.sub.2 OCH.sub.3),
2,2,2-trifluoroethyl difluoromethyl ether (CF.sub.3 CH.sub.2 OCHF.sub.2),
perfluorodiethyl ether, perfluorodipropyl ether and perfluoroethyl propyl
ether, oligomers of perfluoropropylene oxide having a maximum boiling
point of 140.degree. C., perfluorotetrahydrofuran,
perfluoroalkyltetrahydrofurans and perfluorofuran. Aliphatic or
cycloaliphatic, fluorinated or perfluorinated hydrocarbons which are gases
at room temperature, e.g. perfluoropropane, perfluorobutane or
perfluorocyclobutane, which can be liquefied under pressure, for example
up to about 25 bar, mixed and emulsified are also highly suitable.
However, physical blowing agents (dii) which have proven eminently suitable
and are therefore preferred are aliphatic or cycloaliphatic, fluorinated
or perfluorinated hydrocarbons which are liquid at room temperature. The
fluorinated hydrocarbons used are expediently those which are
predominantly, for example at least 85%, fluorinated and contain at least
one, preferably one, bonded hydrogen atom. Examples of suitable
fluorinated hydrocarbons are trifluoromethane, difluoromethane,
difluoroethane, tetrafluoroethane and preferably hexafluoropropane,
heptafluoropropane, 1-H-perfluorobutane and 1-H-perfluorohexane. Examples
of suitable perfluorinated hydrocarbons are perfluoropentane,
perfluorohexane, perfluoroheptane, perfluorooctane, perfluorocyclopentane
and perfluorocyclohexane. The fluorinated or perfluorinated hydrocarbons
or mixtures thereof, like the other suitable physical blowing agents, can
be employed individually or in the form of mixtures. It is also possible
to use mixtures of the different physical blowing agents.
Examples of blowing agent mixtures of this type which may be mentioned are
those which contain
di) at least one vinylfluoroalkane from the group comprising
vinylperfluoroisopropane and preferably vinylperfluoro-n-butane, and
dii) at least one partially fluorinated hydrocarbon from the group
comprising hexafluoropropane, heptafluoropropane, 1-H-perfluorobutane and
1-H-perfluorohexane, and/or at least one partially fluorinated ether from
the group comprising 2,2,2-trifluoroethyl methyl ether and
2,2,2-trifluoroethyl difluoromethyl ether.
The blowing agent mixtures (d) which can be used according to the invention
advantageously contain the vinylfluoroalkane (di) and the further physical
blowing agent (dii), preferably the fluorinated and/or perfluorinated
hydrocarbon, in a weight ratio of from 90:10 to 10:90, preferably from
80:20 to 60:40. If the other physical blowing agent (dii) is insoluble in
the starting components (a), (b) and (c) in the necessary amounts, it is
expediently emulsified in at least one of these starting components
together with the vinylfluoroalkanes (di).
In addition to the vinylfluoroalkanes (di) which can be used according to
the invention as blowing agent, or a mixture of (di) and another physical
blowing agent (dii) which is different from (di), or in place of the
physical blowing agent which is different from (di), it is also possible
to use a chemical blowing agent. A particularly proven chemical blowing
agent is water, which reacts with the organic, modified or unmodified
polyisocyanate (a) to form carbon dioxide, the actual blowing agent and
urea groups, and thus effects the compressive strength of the end
products. Other suitable chemical blowing agents are organic mono- and
polycarboxylic acids having a molecular weight of from 60 to 300 and
preferably formic acid, and ammonium and/or amine salts of formic acid
and/or of the abovementioned mono- and/or polycarboxylic acids, so long as
these react with isocyanates under the reaction conditions and form carbon
dioxide.
The organic carboxylic acids used are advantageously aliphatic mono- and
polycarboxylic acids, e.g. dicarboxylic acids. However, other organic
mono- and polycarboxylic acids are also suitable. The organic carboxylic
acids may, if desired, also contain bonded substituents which are inert
under the reaction conditions of the polyisocyanate polyaddition or are
reactive with isocyanate, and/or may contain olefinically unsaturated
groups. Specific examples of chemically inert substituents are halogen
atoms, such as fluorine and/or chlorine, and alkyl, e.g. methyl or ethyl.
The substituted organic carboxylic acids expediently contain at least one
further group which is reactive toward isocyanates, e.g. a mercapto group,
a primary and/or secondary amino group or preferably a primary and/or
secondary hydroxyl group.
Suitable carboxylic acids are thus substituted or unsubstituted
monocarboxylic acids, e.g. acetic acid, propionic acid, 2-chloropropionic
acid, 3-chloropropionic acid, 2,2-dichl | | |
