Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LeA 24,794
A PROCESS FOR THE PRODUCTION OF FOAMS
BASED ON AROMATIC ISOCYANATES USING
MG(OH)2 AND THE FOAMS PRODUCED THEREBY
BACKGROUND OF THE INVENTION
The present invention relates to a process for the
production of combustion-modified foams and to the foams
produced by that process.
Foams based on aromatic isocyanates are known to be
flammable if they have not been treated in some manner to
increase their fire resistance~
Side effects of combustion such as the optical smoke
density (hereinafter called simply smoke density) may be more of
a hazard in the event of fire than the fire itself. The smoke
density is therefore becoming increasingly important in the
discussions about the risks during fires involving
isocyanate-based foams.
Attempts to protect foams based on aromatic
isocyanates against ignition by the addition of metal compounds
(such as antimony trioxide) have been made. Heavy metal oxides
such as antimony trioxide can reduce the smoke density but often
give rise to the risk of an increased heavy metal load.
The use of Mg(OH)2 has already been proposed for
various plastics materials, for example polyethylene and
polypropylene (see, for example, Plastics Technology, July 1985,
25 page 70 et seq), and for polyurethanes based on hexamethylene
diisocyanates (JA 58-225,116, Hitachi Cable), but not for foams
based on aromatic isocyanates.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide
30 foams based on aromatic isocyanates which produce a low smoke
density in a fire without increasing the heavy metal load. It
is also an object of this invention to provide a process for the
production of such foams.
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These and other objects which will be apparent to
those skilled in the art are accomplished by incorporating
Mg(OH)2 into a foam forming mixture.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to the use of Mg(OH)2 in the
production of foams based on aromatic isocyanates and to the
product foams. The Mg(OH)2 does not have the disadvantage of
the heavy metal load but has a smoke-suppressing effect in foams
based on aromatic isocyanates. It is particularly surprising
that this suppression also takes place in foams which contain
combustion modifying agents containing phosphorus or nonionic
halogen (that is, halogen in a Form other than ionic halide).
In the present invention, it is preferable to use
Mg(OH)2 in a quantity of from 4 to 100 parts by weight,
preferably in a quantity of from 4 to 50 parts by weight, more
preferably in a quantity of from 4 to 10 parts by weight, based
on the foam formed from an aromatic isocyanate taken as 100
parts by weight.
It is also preferred to use Mg(OH)2 having a particle
size of from 0.5 to 50 ~m7 most preferably from 5 to 40 ~m.
Although it is more preferred to use Mg(OH)2 alone as
the smoke-reducing agent, it is also preferred to include
Mg(OH)2 during the production of aromatic isocyanate-based foams
containing from 2 to 20 parts by weight, based on the foam taken
as 100 parts by weight, of nonionic halogen and/or phosphorus
compounds.
The production of foams based on isocyanates is known
and is described, for example, in German Offenlegungsschriften
NOS. 1,694,142, 1,694,215 and 1,720,768 and in Kunststoff-
Handbuch, Volume VII, Polyurethane, edited by Vieweg and
Hochtlen, Carl Hanser Verlag, Munich 1966 and in the new edition
of this book, edited by G. Oertel, Carl Hanser Verlag, Munich,
Vienna 1983. These are predominantly urethane and/or
isocyanurate and/or allophanate and/or uretdione and/or urea
and/or carbodiimide group-containing foams. In the present
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invention, Mg(OH)2 is preferably used in the production of
polyurethane and polyisocyanurate foams.
Suitable starting components for the production of the
foams based on aromatic isocyanates include aromatic
polyisocyanates of the type described, for example, by W.
Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to
136, preferably those corresponding to the formula
Q(NCO)n
in which
n represents 2-4 and
Q represents an aromatic hydrocarbon radical containing from 6
to 15 (preferably from 6 to 13) carbon atoms, such as 1,3- and
1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate
and any mixtures of these isomers, diphenylmethane-2,4'- and/or
-4,4'-diisocyanate and napthylene-1,5-diisocyanate. Triphenyl-
methane-4,4',4"-triisocyanate and polyphenylpolymethylene
polyisocyanates of the type obtained by aniline formaldehyde
condensation and subsequent phosgenation (described, for
example, in Ge 874,430 and 848,671) may also be used in the
present invention. It is also possible to use the isocyanate-
group-containing distillation residues produced dur;ng
industrial isocyanate production, optionally dissolved in one or
more of the above-mentioned polyisocyanates. It is also
possible to use any mixtures of the above-mentioned
polyisocyanates.
The commercially available aromatic polyisocyanates
such as 2,4- and 2,6-tolylene diisocyanate and any mixtures of
these isomers ("TDI"), polyphenyl-polymethylene polyisocyanates
of the type produced by aniline formaldehyde condensation and
subsequent phosgenation ("crude MDI"), and polyisocyanates
containing carbodiimide groups, urethane groups, allophanate
groups, isocyanurate groups, urea groups or biuret groups
("modified polyisocyanates") derived from 2,4- and/or
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2,6-tolylene diisocyanate or from 4,4'- and/or 2,4'-diphenyl-
methane diisocyanate are particularly preferred.
Starting materials which are reactive towards
isocyanates that may be used to produce foams in accordance with
5 the present invention include compounds containing at least two
hydrogen atoms and which generally have a molecular weight of
from 400 to 10,000. These include amino-group-, thiol-group-,
carboxyl-group-, and preferably hydroxyl-group-containing
compounds, in particular compounds containing from 2 to 8
o hydroxyl groups, specifically those having a molecular weight of
from 1000 to 5000, preferably from 800 to 3000. For example,
polyesters, polyethers, polythioethers, polyacetals,
polycarbonates and polyesteramides containing at least two,
generally from 2 to 8, but preferably from 2 to 4, hydroxyl
15 groups of the type known to be useful in the production of
homogeneous and cellular polyurethanes. Such hydroxyl-group-
containing materials are described in detail, for example, in
DE-OS 3,430,285, on pages 10 to 18. Mixtures of isocyanate
reactive compounds may also be used.
Starting materials which may optionally be used to
produce foams in accordance with the present invention include
compounds containing at least two hydrogen atoms which are
reactive towards isocyanates and have a molecular weight of from
32 to 399. These include compounds containing hydroxyl groups
and/or amino groups and/or thiol groups and/or carboxyl groups,
preferably compounds containing hydroxyl groups and/or amino
groups which serve as chain extenders or crosslinking agents.
These compounds generally contain from 2 to 8, preferably from 2
to 4, hydrogen atoms capable of reacting with isocyanates.
Mixtures of various compounds containing at least two hydrogen
atoms capable of reacting towards isocyanates and having a
molecular weight of from 32 to 399 can be used. Examples of
such compounds are described in detail, for example, in DE-OS
3,430,285, on pages 19 to 23.
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Suitable blowing agents for producing foams in
accordance with the present invent;on include water and/or
readily volatile inorganic or organic substances. Appropriate
organic blowing agents include acetone, ethylacetate, and
halogen-substituted alkanes such as monofluorotrichloromethane,
chlorodifluoromethane, dichlorodifluoromethane. Suitable
inorganic blowing agents include air, C02, and N20. A blowing
action can also be achieved by addition of compounds which
decompose at temperatures above room temperature with
elimination of gases, such as nitrogen. Such compounds include,
for example, azo compounds such as azodicarbonamide and
azo;sobutyr;c acid nitrile. Further examples of blowing agents
and details about the use of blowing agents are disclosed in
Kunststoff-Handbuch, Volume VII, edited by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich 1966, for example on pages 108 and
109, 453-455 and 507 to 510.
Substances which may optionally be used as auxiliaries
and additives in the production of foams include catalysts,
surface acti~e additives, reaction retarders, cell regulators,
pigments, fillers, and other anxil;aries and additives known in
the art.
Catalysts of the known type, for example, tertiary
amines such as triethylamine, tributylamine, N-methylmorpholine,
N-ethylmorpholine, N,N,N',N'-tetramethyl-ethylene diamine,
pentamethyl-diethylene triamine and higher homologs (DE-OS
2,624,527 and 2,624,528), 1,4-d;azabicyclo[2.2.2]octane,
N-methyl-N'-dimethylaminoethylpiperazine, bis(dimethylam;no-
alkyl)piperaz;nes, DE-OS 2,636,787), N,N-dimethylbenzylam;ne,
N,N-dimethylcyclohexylamine, N,N-diethylbenzylamine,
bis(N,N-diethylaminoethyl) adipate, N,N,N',N'-tetramethyl-
1,3-butanediamine, N,N-dimethyl-2-phenylethylamine, 1,2-
dimethyl;m;dazole, 2-methyl;midazole, monocyclic and bicyclic
amidines (DE-OS 1,720,633), bis(dialkylamino)alkyl ether (US
Patent 3,330,782, DE-AS 030,558, DE-OS 17804,361 and 2,618,280)
and amide group- (preferably formamide group-) containing
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tertiary amines according to DE-OS 2,~23,633 and 2,732,292) may
be used. Known Mannich bases of secondary amines such as
dimethylamine, aldehydes, preferably formaldehyde, ketones such
as acetone, and phenols may also be used as catalysts. Tertiary
amines containing hydrogen atoms which are active towards
isocyanate groups as catalysts include triethanolamine,
triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanol-
amine, N,N-dimethylethanolamine, the reaction products thereof
with alkylene oxides such as propylene oxide and/or ethylene
ox;de, as well as secondary-tertiary amines disclosed in DE-OS
2,732,292.
Suitable catalysts also include silaamines with
carbon-silicon bonds of the type described, for example, in
DE-PS 1,229,290 (corresponding to US Patent 3,620,984).
2,2,4-Trimethyl-2-silamorpholine and 1,3-diethylaminoethyl-
tetramethyl-disiloxane are specific examples.
Nitrogen-containing bases such as tetraalkylammonium
hydroxides, alkali hydroxides such as sodium hydroxide, alkali
phenolates such as sodium phenolate, and alkali alcoholates such
as sodium methylate may also be used as catalysts.
Hexahydrotriazines (DE-OS 1,769,043), as well as amide group-
(preferably formamide group-) containing tertiary amines
according to DE-OS 2,523,633 and 2,732,292 can also be used as
catalysts.
Organic metal compounds, ;n part;cular organ;c t;n
compounds may also be used in accordance with the present
invent;on as catalysts. Examples of organ;c t;n compounds
include sulfur-containing compounds such as d;-n-octyl-t;n
mercapt;de (DE-AS 1,769,367; US Patent 3,645,927), preferably
t;n(II) salts of carboxylic ac;ds, such as t;n(II) acetate,
tin(II) octoate, tin(II) ethylhexoate and tin(II) laurate, and
t;n(IV) compounds such as d;butyl t;n dilaurate.
Ali of the above-ment;oned catalysts may also be used
as m;xtures.
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Further examples of catalysts and details about the
mode of operation of the catalysts are disclosed in
Kunststoff-Handbuch, Volume VII7 edited by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich 1966, for example on pages 96 to 102.
If a catalyst is used, it is generally used in a
quantity of between about 0.001 and 10% by weight, based on the
quantity of aromatic polyisocyanate.
Surface-active additives such as emulsifiers and foam
stabilizers may also be included in foam forming mixtures.
o Suitable emulsifiers include the sodium salts of castor oil
sulfonates or salts of fatty acids with amines such as oleic
acid diethylamine and stearic acid d;ethanolamine. Alkali or
ammonium salts of sulfonic acids such as dodecylbenzol sulfonic
acid, dinaphthylmethane disulfonic acid (e.g., ricinoleic acid)
and polymeric fatty acids may also be used as surface-active
additives.
Su;table foam stabilizers include polyether siloxanes,
particularly water-soluble polyether siloxanes. These compounds
are generally made up in such a way that a copolymer of ethylene
oxide and propylene oxide is bound to a polydimethyl siloxane
radical. Foam stabilizers of this type are described, for
example, in U.S. Patents 2,834,748, 2,917,480 and 3,629,308.
Polysiloxane polyoxyalkylene copolymers which are branched via
allophanate groups (disclosed in DE-OS 2,558,523) are of
particular ;nterest in many cases.
Reaction retarders such as acid compounds (e.g.
hydrochloric acid and organic acid halides); known cell
regulators such as paraffins, fatty alcohols and dimethyl-
polysiloxanes; pigments; dyes; stabilizers against ageing and
weathering effects; plasticizers; fungistatically and
bacteriostatically acting substances; and fillers such as barium
sulphate, diatomaceous earth, carbon black and whiting may also
be included in the foam forming components used to produce foams
in accordance with the present invention.
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Further examples of surface-active additives, foam
stabilizers, cell regulators, reaction retarders, plasticizers,
dyes, fillers and fungistatically and bacteriostatically active
substances which may optionally be used according to the
invention as well as details about the method of use and mode of
operation of these additives are disclosed in Kunststoff-
Handbuch, Volume VII, edited by Vieweg and Hochtlen, Carl-
Hanser-Verlag, Munich 1966, for example on pages 103 to 113.
Any of various known combustion modifying agents
containing phosphorus and/or halogen in a form other than ionic
halide are useful in the process of this invention. Suitable
combustion modifying agents of this type include trischloroethyl
phosphate, dimethyl methanephosphonate, tricresyl phosphate,
ammonium phosphate, and ammonium polyphosphate.
In the process of the present invention, the reaction
components may be reacted by the known single stage process, the
prepolymer process or the semi-prepolymer process. Generally
the reactants are used in quantities such that the NC0 Index is
from 50 to 300, preferably from 95 to 250. Examples of
appropriate apparatus are described, for example, in U.S. Patent
2,764,565. Details about processing devices which may be used
in the practice of the present invention are disclosed in
Kunststoff-Handbuch, Volume VII, edited by Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich 1966, for example on pages 121 to
205.
Foam production may take place in closed molds. In
this case, the reaction mixture is introduced into a mold.
Suitable mold materials include metals (for example, aluminum)
and plastics (for example, epoxide resins). The reaction
mixture foams in the mold and forms the shaped article. Foaming
in the mold can be carried out in such a way that the molded
product has a cellular structure on its surface. Foaming may
also be carried out in such a way that the molded product has a
dense skin and a cellular core. It is also possible to mold in
such a way that sufficient reaction mixture is introduced into
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the mold for the foam formed to just fill the mold. It is also
possible to introduce more foamable reaction mixture into the
mold than is required to fill the mold cavity with foam. In the
latter case, "overcharging" takes place. Such a mode of
operation is disclosed, for example, in U.S. Patents 3,178,490
and 3,182,104.
When carrying out foaming in a mold, known "external
release agents" such as silicon oils are often used. However,
so-called "internal release agents" may also be used, optionally
o mixed with external release agents, of the type described for
example, in DE-OS 2,121,670 and 2,307,587.
Foams can also be produced by block foaming or by the
known laminator process.
The foams obtainable by the invention may be used as
insulating boards such as roof insulation.
The invention is further illustrated but is not
intended to be limited by the following examples in which all
parts and percentages are by weight unless otherwise specified.
EXAMPLES
The invention is described in more detail in the
following Examples and Comparison Examples.
Examples B and F (according to the invention) have
lower smoke densities than Comparison Examples A and E.
Comparison Example C shows that the use of phosphorus and
nonionic halogen leads to an increase in the smoke density
relative to Comparison Example A. However, the smoke density is
also reduced relative to Comparison Example C by the use of
Mg(OH)2, as shown by Example D (according to the invention).
As shown in Examples G and H in comparison with
Example B, the average particle size of the Mg(OH)2 has a
considerable influence on smoke suppression. Mg(OH)2 is most
preferably used in particle sizes of from 25 to 40 ~m.
The smoke density is examined by the testing method
described in ASTM-D-2843-70. The data show the "smoke density
ratings" determined by this method.
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Although the invention has been described in detail
in the foregoing for the purpose of illustration, it is to be
understood that such deta;l is solely for that purpose and
that variations can be made therein by those skilled ;n the
art without departing from the spirit and scope of the
invention except as it may be limited by the claims.
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