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Description  |
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This invention relates to a process for the production of foamed synthetic
materials preferably based on polyisocyanates, in particular polyurethane
foams, using 1,1,1-trifluoro-2-chloroethane, optionally mixed with
1,1,-difluoro-1,2-dichloroethane.
The production of foamed synthetic materials, e.g. of polyurethanes, with
the aid of blowing agents based on fluorochlorinated hydrocarbons is known
(see e.g. German Pat. No. 1,045,644).
Blowing agents based on fluorochlorinated hydrocarbons, particularly
trichlorofluoromethane (R11) and to a less extent dichlorodifluoromethane
(R12) and 1,1,2-trichlorotrifluoroethane (R113) are of great technical
importance because they enable, for example, rigid polyurethane foams to
be produced in which from 90 to 95% of the cells are closed. The R11
enclosed in the cells is mainly left in them and owing to its advantageous
physical properties it gives rise to a foam which has a very low thermal
conductivity (see O. Scherer, Technische organische Fluorverbindungen,
Fortschr. Chem. Forsch., Vol. 14/2, p. 147 (1968)). Such rigid
polyurethane foams are used mainly as insulation against heat and cold in
refrigeration apparatus, cold storage rooms, pipes, containers and
structural elements and as packaging material and for surface protection.
The possible uses thereof in this field are even further increased by the
trend to energy saving methods of building by improved insulation.
The use of halogen-substituted alkanes, in particular R11 and R12, was
first described in German Pat. No. 1,045,644.
If halogenated alkanes are to be suitable for use as gaseous blowing
agents, they must have certain properties, such as a suitable boiling
point or vapor pressure, solubility or dispersibility in one of the
reactants, for example in the polyester or the polyether, low thermal
conductivity, non-toxicity, chemical inertness, non-combustibility, low
rate of diffusion, the ability to prevent shrinkage of the foam and
freedom from a tendency to swell the cell walls.
The above-mentioned fluorochloroalkanes may be used not only for the
production of flexible, semi-rigid and rigid foams based on
polyisocyanates, such as polyurethane foams, but also for the production
of foams based on polyolefins, polystyrenes and phenol resins, for which
various techniques are employed, such as direct foaming, prefoaming
(frothing method) or direct gassing in the extruder. (see e.g. Company
publication by Kali-Chemie AG, Hanover (1976): "Kaltron, das Treibmittel
fur Schaumstoffe").
Since perhalogenated fluoro chloroalkanes are very difficult to degrade
(see e.g. Nature 249, 810 (1974); Symposium Report of the Gottlieb
Duttweiler Institute, Ruschlikon/Zurich, 17/18.2.1977; Aerosol Report,
Vol. 16, No. 1/1977, pages 12 and 13), there is a serious need for
alternative blowing agents which resemble perhalogenated fluoroalkanes in
the advantageous properties thereof, but are easily degraded and therefore
ecologically harmless.
A process for the production of foamed synthetic materials, in particular
of polyurethane foams, has now been found which completely satisfies this
requirement, in which process 1,1,1-trifluoro-2-chloroethane is used as
blowing agent, optionally mixed with 1,1-difluoro-1,2-dichloroethane.
The present invention relates to a process for the production of foamed
synthetic materials by carrying out the reaction of starting materials for
a polymerization, polycondensation or polyaddition reaction to produce
high molecular weight synthetic resins in the presence of blowing agents
or by foaming an unfoamed thermoplastic synthetic resin by means of a
blowing agent in known manner, characterized in that the blowing agent
used is 1,1,1-trifluoro-2-chloroethane, optionally as a mixture with
1,1-difluoro-1,2-dichloroethane.
It has surprisingly been found that 1,1,1-trifluoro-2-chloroethane (R
133a), optionally mixed with 1,1-difluoro-1,2-dichloroethane (R 132) is a
very suitable blowing agent for the production of foamed synthetic
materials, in particular those based on polyurethanes. The quality of the
foams produced using these blowing agents is substantially equal to that
of products which have been conventionally produced, e.g. using CFCl.sub.3
(R11). When R 132 is mixed with R 133a it is generally in up to about 80%
and preferably from about 20 to 80% by weight of the mixture of the two.
R 133a and R 132 are incombustible and according to all tests so far
carried out they are physiologically harmless (see e.g. Nachrichten Chemie
und Technik 24, 1976, page 307 and Aerosol Age, January 1977, page 9).
Both substances are readily degradable under the influence of light. The
tropospheric life of 133a is only 6.1 years (von Schweinichen, Aerosol
Report, April 1977, page 172-180). When assessing this figure, one must
take into account that R 133a has only one chlorine atom whereas R 11
which is conventionally used has three chlorine atoms. Experiments carried
out by the present applicants show that when CFCl.sub.3 is irradiated for
24 hours (Osram-Ultra-Vitalux-Lamps) using radiation corresponding
approximately to natural sunlight at a height of several thousand meters,
it decomposes to an extent of 0.04% (determined from the resulting
quantity of chlorine ions) or 0.13% (determined from the resulting
quantity of fluorine ions). The corresponding degrees of decomposition of
CF.sub.3 CH.sub.2 Cl are 53% and 46%.
Both R 133a and its preliminary product R 132 are easily prepared in high
yields and excellent purity (greater than 99.99%) by catalytic liquid
phase fluorination of unstabilized trichloroethylene, which is an
inexpensive mass-produced starting material (German Offenlegungsschrift
No. 2,719,021).
Furthermore, it should be noted that in spite of its tropospheric
degradability, R 133a has a high thermal and chemical stability, e.g.
towards hydrolytic influences and nucleophilic attacks (for example of OH
ions or amines). A specially stabilized quality, such as is required when
using R 11 for foaming polyurethanes in cases where previously mixed
systems of polyols, amine-based catalysts, silicone stabilizers and
blowing agents are kept for some time before foaming, is not necessary
when using R 133a (or R 132) (see L. M. Zwolinski, Rubber Age, July 1975,
page 54). The processing of amine-based polyols may also be carried out
quite problem-free with the aid of the new blowing agents.
It is also surprising that R 133a is suitable for use as blowing agent for
the production of foam plastics in spite of its substantially lower
boiling point of 6.9.degree. C. compared with that of R 11 (R
11=23.7.degree. C.). This is presumably the cause of its ready solubility
in the foaming components.
The additional use of R 132 (b.p.=46.8.degree. C.) is suitable in cases
where relatively high foaming temperatures occur or where the raw material
is stored at relatively high temperatures so that the vapor pressure of
the blowing agent becomes too high. In such cases, R 113 (CF.sub.2
Cl-CFCl.sub.2, b.p.=47.7.degree. C.) which is normally used in such cases
may be replaced R 132 because R 113, being a perhalogenated alkane, like R
11 is very difficult to degrade.
Production of the foams is carried out by known methods (see Houben-Weyl,
Methoden der organischen Chemie, Vol. XIV/2, page 88 (1963); High
Polymers, Vol. XVI, "Polyurethanes Chemistry and Technology", by
Saunders-Frisch, Interscience Publishers, New York/London, 1962/1964;
Kunststoffhandbuch, Volume VII, Vieweg-Huchtlen, Carl-Hanser-Verlag
Munich, 1966).
The process according to the present inventiion is suitable for the
production of various cellular and porous materials, in particular for the
production of foams of synthetic materials. The synthetic materials may be
produced by polymerization or polyaddition, and also by polycondensation.
The following are mentioned as examples of synthetic materials:
polyolefins, such as polyethylene or polypropylene, polystyrene,
polyethylstyrene, polyamide, polycarbonate, polysulphone, polyethylene
terephthalate, polybutylene terephthalate, polyphenylene oxide,
polymethacrylate, polymethacrylonitrile, polyacrylonitrile, polyvinyl
chloride, synthetic materials based on cellulose esters, copolymers of the
above-mentioned components, acrylonitrile-butadiene-styrene polymers
(ABS), mixtures of polysulphone and styrene-acrylonitrile or ABS polymers,
mixtures of polycarbonate and ABS polymers, and mixtures of polyvinyl
chloride and ABS polymers of styrene-acrylonitrile. Foams of
inorganic-organic materials may also be produced according to the present
invention, e.g. the synthetic materials described in French Pat. Nos.
1,419,552 and 1,362,003; German Offenlegungsschrift Nos. 1,770,384;
2,227,147; 2,310,559; 2,325,090; 2,359,610; 2,359,607; 2,359,606;
2,359,608; 2,359,609 and 2,359,612.
The blowing agent according to the present invention is preferably added in
quantities of about 0.01 to 40%, by weight, most preferably about 0.1 to
30%, by weight, based on the synthetic material or based on the reaction
mixture which reacts to produce the synthetic material, but it may also be
used in any other quantity familiar to those skilled in the art. The
quantity added depends in the individual case on the requirements to be
fulfilled by the foamed product.
The blowing agent according to the present invention may also be used in
combination with known auxiliary agents, such as nucleating agents or
nucleus-forming agents (e.g. talcum, MgCO.sub.3, CaCO.sub.3, ZnCO.sub.3,
CaSO.sub.4, NaHCO.sub.3, polytetrafluoroethylene powder or
polyhexafluoropropylene powder), fillers (e.g. glass fibers, CaCO.sub.3,
MgCO.sub.3, chalk, kaolin or TiO.sub.2), lubricants (e.g. waxes, paraffins
or fatty acid esters), stabilizers (e.g. UV absorbents or light and heat
stabilizers), bonding agents (e.g. paraffin oil, plasticizers, butyl
stearate or resin solutions), chemical fillers (e.g. SiO.sub.2, MgO, ZnO
or ZnCO.sub.3), peroxides, pigments, dyes, antioxidants and/or
antiozonants.
The process according to the present invention is therefore suitable for
the production of any foams in which "physical blowing agents" have
hitherto been used, i.e. in which the action of the blowing agent is due
to evaporation of a readily volatile inert liquid. The preferred foams
obtainable by the process according to the present invention include the
known foams based on polyisocyanates. The known polyurethane foams are
particularly preferred. In addition to polyurethane foams, which are
particularly preferred, the polyisocyanate-based foams also include foams
containing isocyanurate groups, which foams are obtained by the known
process of trimerization of organic polyisocyanates during the reaction
which results in the foam; also foams containing carbodiimide groups,
which are obtained in known manner by the condensation of isocyanate
groups accompanied by the formation of carbodiimide groups during the
reaction by which the foam is formed; mixed types (containing isocyanurate
and carbodiimide groups and in some cases also urethane groups) which are
obtained by the reaction of polyisocyanates with sub-equivalent quantities
of polyhydroxyl compounds in the presence of trimerization catalysts
and/or carbodiimidization catalysts; and inorganic-organic foams obtained,
for example, by the reaction of polyisocyanates with alkali metal silicate
solutions and/or dispersions, optionally in the presence of additives,
according to the above-mentioned publications.
The polyisocyanates used as starting components in the preferred process
for the production of foamed synthetic materials based on polyisocyanates
may be any aliphatic, cycloaliphatic, araliphatic, aromatic or
heterocyclic polyisocyanates, such as those described, for example, by W.
Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, but
they should preferably be liquid at room temperature. The following are
examples: ethylene diisocyanate, tetramethylene-1,4-diisocyanate,
hexamethylene-1,6-diisocyanate, dodecane-1,12-diisocyanate,
cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate and
mixtures of these isomers,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (German
Auslegeschrift No. 1,202,785, U.S. Pat. No. 3,401,190),
hexahydrotolylene-2,4-diisocyanate and -2,6-diisocyanate and mixtures of
these isomers, hexahydrophenylene-1,3-diisocyanate and/or
1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate and/or
4,4'-diisocyanate, phenylene-1,3-diisocyanate and -1,4-diisocyanate,
tolylene-2,4-diisocyanate and -2,6-diisocyanate and mixtures of these
isomers, diphenylmethane-2,4'-diisocyanate and/or 4,4'-diisocyanate,
naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate,
polyphenyl-polymethylene polyisocyanates which may be obtained by
aniline/formaldehyde condensation followed by phosgenation and which have
been described, for example, in British Pat. Nos. 874,430 and 848,671, m-
and p-isocyanatophenyl-sulphonyl isocyanates according to U.S. Pat. No.
3,454,606, perchlorinated aryl polyisocyanates, such as those described,
for example, in German Auslegeschrift No. 1,157,601 (U.S. Pat. No.
3,277,138), polyisocyanates containing carbodiimide groups, as described
in German Pat. No. 1,092,007 (U.S. Pat. No. 3,152,162), diisocyanates of
the type described in U.S. Pat. No. 3,492,330, polyisocyanates containing
allophanate groups as described, e.g. in British Pat. No. 994,890, in
Belgian Pat. No. 761,626 and in published Dutch patent application No.
7,102,524, polyisocyanates containing isocyanurate groups, e.g. as
described in U.S. Pat. No. 3,001,973, in German Pat. Nos. 1,022,789;
1,222,067 and 1,027,394 and in German Offenlegungsschrift Nos. 1,929,034
and 2,004,048, polyisocyanates containing urethane groups as described,
e.g. in Belgian Pat. No. 752,261 or in U.S. Pat. No. 3,394,164
polyisocyanates containing acylated urea groups according to German Pat.
No. 1,230,778, polyisocyanates containing biuret groups as described, e.g.
in German Pat. No. 1,101,394 (U.S. Pat. Nos. 3,124,605 and 3,201,372) and
in British Pat. No. 889,050, polyisocyanates prepared by telomerization
reactions as described, for example, in U.S. Pat. No. 3,654,106,
polyisocyanates containing ester groups, such as those mentioned, for
example, in British Pat. Nos. 965,474 and 1,072,956, in U.S. Pat. No.
3,567,763 and in German Pat. No. 1,231,688, reaction products of the
above-mentioned isocyanates with acetals according to German Pat. No.
1,072,385 and polyisocyanates containing polymeric fatty acid groups
according to U.S. Pat. No. 3,455,883.
It is preferred to use the readily available polyisocyanates which are
normally used for the production of polyisocyanate-based foams, in
particular the production of polyurethane foams, on a large technical
scale. Examples of such isocyanates include: 2,4-diisocyanato-toluene,
2,6-diisocyanatotoluene, mixtures of these isomers,
4,4'-diisocyanatodiphenylmethane, 2,4'-diisocyanatodiphenylmethane,
polyisocyanate mixtures of the diphenylmethane series containing these
isomers, as well as higher homologues of these diisocyanates, which
mixtures may be obtained by the known process of phosgenating
aniline/formaldehyde condensates; diphenylmethane diisocyanates containing
carbodiimide and/or urethoneimine groups, such as the diisocyanates
obtained according to German Pat. No. 1,092,007 (U.S. Pat. No. 3,152,162);
and polyisocyanates containing urethane groups, such as those obtained by
the reaction of 1 mol of 4,4-diisocyanatodiphenylmethane with from 0.05 to
0.3 mol of low molecular weight diols or triols, preferably polypropylene
glycols having a molecular weight of below 700. Mixtures of the
last-mentioned preferred polyisocyanates are also preferred.
The starting components used according to the present invention may also
include compounds, generally having a molecular weight of about 62 to
10,000, which contain at least two isocyanate-reactive hydrogen atoms.
These may be compounds containing amino groups, thiol groups or carboxyl
groups, but are preferably polyhydroxyl compounds, in particular compounds
containing from 2 to 8 hydroxyl groups, especially those having a
molecular weight of about 200 to 10,000, preferably about 1000 to 6000,
e.g. polyesters, polyethers, polythioethers, polyacetals and polyester
amides having at least two, generally from 2 to 8, preferably from 2 to 4,
hydroxyl groups, such as the compounds known for the production of
cellular and non-cellular polyurethanes. In the process according to the
present invention, it is often advantageous to use the above-mentioned
relatively high molecular weight polyhydroxyl compounds as mixtures with
up to about 95%, by weight, preferably up to about 50%, by weight, based
on the total quantity of polyhydroxyl compounds, of low molecular weight
polyols having a molecular weight of about 62 to 200. The following are
examples of such low molecular weight polyols: ethylene glycol,
propane-1,2-diol, propane-1,3-diol, butane-1,2-diol, butane-1,4-diol,
hexane-1,6-diol, decane-1,10-diol, diethylene glycol, triethylene glycol,
tetraethylene glycol, dipropylene glycol, tripropylene glycol, glycerol,
trimethylolpropane, and the like.
Suitable polyesters containing hydroxyl groups include, e.g. reaction
products of polyhydric, preferably dihydric alcohols, optionally with the
addition of hydric alcohols, and polybasic, preferably dibasic, carboxylic
acids. Instead of free polycarboxylic acids, the corresponding
polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters
of lower alcohols or mixtures thereof may be used for preparing the
polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic,
aromatic and/or heterocyclic and they may be substituted, e.g. by halogen
atoms, and/or may be unsaturated. The following are mentioned as examples:
succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid,
phthalic acid, isophthalic acid, trimellitic acid, phthalic acid
anhydride, tetrahydrophthalic acid anhydride, hexahydrophthalic acid
anhydride, tetrachlorophthalic acid anhydride, endomethylene
tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid,
maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids,
such as oleic acid, optionally mixed with monomeric fatty acids, dimethyl
terephthalate and terephthalic acid-bis-glycol esters. The following are
examples of suitable polyhydric alcohols: ethylene glycol, propylene
glycol-(1,2) and -(1,3), butylene glycol-(1,4) and -(2,3),
hexanediol-(1,6), octanediol-(1,8), neopentyl glycol, cyclohexane
dimethanol (1,4-bis-hydroxymethylcyclohexane), 0.001 to 10% by weight,
based on the quantity of compounds having at least two isocyanate-reactive
hydrogen atoms and a molecular weight of about 62 to 10,000.
Surface active additives (emulsifiers and foam stabilizers) may also be
used according to the present invention. Suitable emulsifiers include,
e.g. the sodium salts of ricinoleic sulphonate or of fatty acids or salts
of fatty acids with amines, such as oleic acid diethylamine or stearic
acid diethanolamine. Alkali metal or ammonium salts of sulphonic acids,
such as dodecylbenzene sulphonic acid or dinaphthylmethane disulphonic
acid, or of fatty acids, such as ricinoleic acid, or of polymeric fatty
acids may also be used as surface active additives.
Suitable foam stabilizers are particularly the watersoluble polyether
siloxanes. These compounds generally have oxide, propylene oxide, butylene
oxide, tetrahydrofuran, styrene oxide or epichlorohydrin, either on their
own, e.g. in the presence of BF.sub.3, or by addition to these epoxides,
optionally as mixtures or successively, to starting components having
reactive hydrogen atoms, such as alcohols or amines, e.g. water, ethylene
glycol, propylene glycol-(1,3) or -(1,2), trimethylolpropane,
4,4'-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine or ethylene
diamine. Sucrose polyethers may also be used according to the present
invention, e.g those described in German Auslegesschrift Nos. 1,176,358
and 1,064,938. It is in many cases preferred to used polyethers which
contain predominantly primary OH groups (up to 90%, by weight, based on
all the OH groups present in the polyether). Polyethers modified with
vinyl polymers, e.g. the compounds obtained by polymerization of styrene
or acrylonitrile in the presence of polyethers (U.S. Pat. Nos. 3,383,351;
3,304,273; 3,523,093 and 3,110,695 and German Pat. No. 1,152,536) are also
suitable, as well as polybutadienes which have OH groups.
Particularly to be mentioned among the polythioethers are the condensation
products obtained by reacting thiodiglycol on its own and/or with other
glycols, dicarboxylic aicds, formaldehyde, aminocarboxylic acids or amino
alcohols. The products obtained are polythio mixed ethers, polythio ether
esters or polythio ether ester amides, depending on the co-components.
Suitable polyacetals include, for example, the compounds which may be
prepared from the reaction of glycols, such as diethylene glycol,
triethylene glycol, 4,4'-dioxethoxy-diphenyl dimethylmethane and hexane
diol, with formaldehyde. Suitable polyacetals for the purposes of the
present invention may also be prepared by the polymerization of cyclic
acetals.
The polycarbonates containing hydroxyl groups used may be of the known
type, for example those which may be prepared by the reaction of diols,
such as propane diol-(1,3), butane diol-(1,4) and/or hexane diol-(1,6),
diethylene glycol, triethylene glycol or tetraethylene glycol, with diaryl
carbonates, e.g. diphenyl carbonate, or with phosgene.
Suitable polyester amides and polyamides include, for example, the
predominantly linear condensates prepared from polybasic saturated and
unsaturated carboxylic acids or the anhydrides thereof and polyfunctional
saturated and unsaturated amino alcohols, diamines, polyamines and
mixtures thereof.
Polyhydroxyl compounds already containing urethane or urea groups and
modified or unmodified natural polyols, such as castor oil, carbohydrates
or starch may also be used. Addition products of alkylene oxides and
phenol/formaldehyde resins or of alkylene oxides and urea/formaldehyde
resins are also suitable for the purposes of the present invention.
Representatives of these compounds which may be used according to the
present invention have been described, for example, in High Polymers, Vol.
XVI, "Polyurethanes, Chemistry and Technology" by Saunders-Frisch,
Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and
pages 44-54 and Volume II, 1964, pages 5-6 and 198-199 and in
Kunststoff-Handbuch, Volume VII, Vieweg-Hochtlen, Carl-Hanser-Verlag,
Munich, 1966, e.g. on pages 45 to 71.
The reactants are preferably put into the process according to the present
invention in proportions corresponding to an isocyanate index of about 70
to 800, preferably about 90 to 130 (an isocyanate index of 100 corresponds
to the presence of equivalent quantities of isocyanate groups and
isocyanate-reactive hydrogen atoms in the reaction mixture).
According to the present invention, other organic compounds may also be
used as blowing agents, but they should preferably be readily volatile.
Suitable organic blowing agents include, for example, acetone, ethyl
acetate, halogen-substituted alkanes which are degradable in the
stratosphere, such as methylene chloride, chloroform, ethylidene chloride
and vinylidene chloride, and butane, hexane, heptane and diethyl ether.
According to a preferred method of carrying out the process according to
the present invention, the blowing agents used consist of azeotropic
mixtures of the blowing agents which are an essential feature of the
present invention and other environmentally harmless blowing agents of the
type exemplified above, so that the boiling point of the blowing agent may
be adjusted as required in each individual case.
Additional compounds which accelerate the isocyanate addition reaction are
also often used in the process according to the present invention, e.g.
organo-metallic compounds, in particular organo-tin compounds, such as
tin(II) acetate, tin(II) octoate, tin(II) ethyl hexoate and tin(II)
laurate, and the dialkyl tin salts of carboxylic acids, e.g. dibutyl tin
diacetate, dibutyl tin dilaurate, dibutyl tin maleate or dioctyl tin
diacetate.
The process according to the present invention may also be modified by the
use of known compounds for catalyzing the trimerization of isocyanates so
that polyurethane foams which contain isocyanurate groups are obtained. In
this embodiment of the process according to the present invention it is
particularly suitable to use isocyanate indices substantially higher than
100 because free isocyanate groups must in this case be available not only
for the reaction with the active hydrogen atoms, but also for
trimerization. The trimerization catalysts used may be any compounds which
initiate a polymerization reaction of the isocyanate group at room
temperature. Such compounds have been described, for example, in French
Patent No. 1,441,565, Belgian Pat. Nos. 723,153 and 723,152 and in German
Offenlegungsschrift No. 2,301,408. They are mainly basic salts, such as
sodium acetate and potassium acetate, or mono-nuclear or higher nuclear
Mannich bases obtained from phenols which are capable of being condensed
and which may be substituted with alkyl, aryl or aralkyl groups, oxo
compounds and secondary amines, especially those Mannich bases in which
the oxo compound used for the preparation thereof was formaldehyde and the
secondary amine was dimethylamine. According to IR spectroscopic analyses,
substantial proportions of carbodiimide structures are formed in the
foams, the proportion in the foams depending on the conditions,
particularly on the reaction temperature reached. The proportion of
carbodiimide structures of the foams may be increased by means of known
catalysts for the preparation of carbodiimides, particularly organic
phosphorus compounds having a valency of from 3 to 5, such as
phospholines, phospholine oxides, tertiary phosphines and the like. The
process according to the present invention may also be carried out
entirely without compounds containing isocyanate-reactive groups so as to
produce foams which contain isocyanurate groups and possibly also
carbodiimide groups, but no urethane groups. The blowing agents according
to the present invention are also eminently suitable for the production of
polyisocyanate-based foams of this type. Further details may be found, for
example, in "Polyurethanes, Chemistry and Technology", Vols. I and II,
Saunders-Frisch, Interscience Publishers, 1962 and 1964.
The quantity of polymerization catalyst to be used is largely determined by
the nature and in some cases basicity of the catalyst. If isocyanurate
groups are to be formed at the same time in the process according to the
present invention, the trimerisation catalysts are generally used in
quantities of about 0.1 to 10%, by weight, preferably about 0.2 to 5%, by
weight, based on the polyisocyanate component.
Other representatives of catalysts which may be used according to the
present invention and details concerning the activity of the catalysts may
be found in Kunststoff-Handbuch, Volume VII, published by Vieweg and
Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 96 to 102.
Catalysts which accelerate the formation of polyurethane are generally used
in quantities of from about 0.001 to 10%, by weight, based on the quantity
of compounds having at least two isocyanate-reactive hydrogen atoms and a
molecular weight of about 62 to 10,000.
Surface active additives (emulsifiers and foam stabilizers) may also be
used according to the present invention. Suitable emulsifiers include,
e.g. the sodium salts of ricinoleic sulphonate or of fatty acids or salts
of fatty acids with amines, such as oleic acid diethylamine or stearic
acid diethanolamine. Alkali metal or ammonium salts of sulphonic acids,
such as dodecylbenzene sulphonic acid or dinaphthylmethane disulphonic
acid, or of fatty acids, such as ricinoleic acid, or of polymeric fatty
acids may also be used as surface active additives.
Suitable foam stabilizers are particularly the water-soluble polyether
siloxanes. These compounds generally have a polydimethyl siloxane group
attached to a copolymer of ethylene oxide and propylene oxide. Foam
stabilizers of tyis type have been described, for example, in U.S. Pat.
No. 2,764,565.
Other additives which may also be used according to the present invention
include reaction retarders, e.g. substances which are acid in reaction,
such as hydrochloric acid or organic acid halides, known cell regulators,
such as paraffins or fatty alcohols or dimethyl polysiloxanes, pigments,
dyes known flame retarding agents, such as tris-chloroethylphosphate or
ammonium phosphate and polyphosphate, stabilizers against ageing and
weathering, plasticizers, fungistatic and bacteriostatic substances and
fillers, such as barium sulphate, kieselguhr, carbon black or whiting.
Other examples of surface active additives, foam stabilizers, cell
regulators, reaction retarders, stabilizers, flame retarding substances,
plasticizers, dyes, fillers and fungistatic and bacteriostatic substances
which may be used according to the present invention and details
concerning the use and mode of action of these additives may be found in
Kunststoff-Handbuch, Volume VII, published in Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich 1966, e.g. on pages 103 to 113.
The process according to the present invention may be employed both for
producing foams under unrestricted conditions and for producing foams
inside molds, especially for producing foams having a non-cellular surface
skin.
For producing such foams inside molds, the reaction mixture is introduced
into a mold which may be made of a metal, e.g. aluminum, or a synthetic
material, e.g. an epoxide resin. The reaction mixture foams inside the
mold to form the molded product. Foaming in the mold may be carried out
either to produce a molded product having a cellular structure on its
surface or to produce a molded product having a non-cellular skin and a
cellular core. According to the present invention, one or other result may
be obtained by either introducing into the mold just sufficient reaction
mixture to fill the mold with foam after the reaction or by introducing a
larger quantity of reaction mixture than is necessary for filling the
interior of the mold with foam. The last-mentioned method is known as
"overcharging", a procedure which has been described, e.g. in U.S. Pat.
Nos. 3,178,490 and 3,182,104. When this last-mentioned method is employed,
foams having a non-cellular surface skin are obtained.
Cold setting foams may also be produced according to the present invention
(see British Pat. No. 1,162,517, German Offenlegungsschrift No.
2,153,086).
The internal mold release agents known in the art, such as those described,
for example, in German Offenlegungsschrift Nos. 1,953,937 and 2,121,670,
may also be used for producing molded foams having a non-cellular surface
skin by the process according to the present invention.
To carry out the process according to the present invention, the starting
components are preferably reacted together by the known one shot process,
often using mechanical devices e.g. those described in U.S. Pat. No.
2,764,565. Details concerning processing apparatus which may also be used
according to the present invention may be found in Kunststoff Handbuch,
Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich
1966, e.g. on pages 121 to 205.
The process may be employed for the production of rigid products used for
the manufacture of furniture parts, car body parts, technical apparatus
and structural elements, as well as for the production of semi-rigid to
flexible products for the manufacture of safety cushioning in the
construction of motor vehicles, elastic shoe soles, shock absorbers, etc.
The process according to the present invention is described in the
following illustrative example:
EXAMPLE
Production of rigid polyurethane foams, using monofluorotrichloromethane
(blowing agent A), 1,1,1-trifluoro-2-chloroethane (blowing agent B) and
1,1-difluoro-1,2-dichloroethane (blowing agent C) as blowing agents. The
foams were produced from the following different formulations:
Formulation I:
85 g of a polyether polyol (OH number 380, viscosity at 25.degree. C.
13,000 mPa.s) obtained by the propoxylation of saccharose;
15 g of a phosphorus-containing flame retarding agent, OH number 450, which
is capable of being chemically fixed in the product;
1.5 g of a silicone stabilizer based on a polysiloxane which is modified
with polyether groups in side positions;
0.5 g of water;
2.0 g of dimethyl cyclohexylamine;
28.0 g of blowing agent;
115 g of a commercial polyisocyanate mixture of the diphenylmethane series,
viscosity 200 mPa.s/20.degree. C., prepared by a phosgenation of
aniline/CH.sub.2 O condensates.
Formulation II:
80 g of a polyether polyol (OH number 380, viscosity at 25.degree. C.
13,000 mPa.s); obtained by the propoxylation of saccharose;
12 g of a polyether polyol (OH number 380, viscosity at 25.degree. C. 600
mPa.s) obtained by the propoxylation of trimethylolpropane;
8 g of a diol (OH number 490) obtained by the ethoxylation of ethylamine;
1.5 g of a silicone stabilizer based on a polysiloxane modified with
polyether groups in side positions;
2.0 g of water;
1.3 g of dimethyl cyclohexylamine;
38 g of blowing agent;
130 g of the commerical polyioscyanate mixture used in formulation I.
The polyols were mixed with the additives and blowing agents by stirring in
a cardboard cup. The quantity of blowing agent evaporating as a result of
the mixing process was replaced, the isocyanate was added and the mixture
was vigorously stirred (all components had been adjusted to a temperature
of 20.degree. C. before mixing). In the case of blowing agent B, the
polyol additive component was first cooled to about 5.degree. C. and
blowing agent was stirred in at this temperature. The mixture was then
carefully warmed to 20.degree. C. As soon as the reaction mixture had been
prepared, it was poured into a mold of packing paper (square base
20.times.20 cm, height 14 cm). The cream time and gel time were measured
during the foaming process.
The data obtained from the measurements carried out on the various
formulations using the various blowing agents are shown in the following
Table:
Table
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Formulation I
Formulation II
Blowing agent
Blowing agent
A B C A B C
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Cream time [s] 30 32 20 13 13 12
Gel time [s] 130 136 87 102 123 95
Gross density [kg/m.sup.3 ]
33 33 26 21 21.5 19
Compressive strength [MPa]
in the direction of foaming
0.23 0.22 0.16 -- -- --
perpendicularly to the
direction of foaming
0.12 0.11 0.10 -- -- --
Dimensional stability
(change in % vol)
3 h, -30.degree. C.
0 0 -2 -- -- --
5 h, +100.degree. C.
0 0 +4 -- -- --
______________________________________
It will be appreciated that the instant specification and examples are set
forth by way of illustration and not limitation and that various
modifications and changes may be made without departing from the spirit
and scope of the present invention.
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