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Description  |
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The invention relates to casting resins which essentially consist of a
mixture of polycarbodiimides in vinyl monomers and which cure by heating
to a temperature above 40.degree. C.
In this case, mixture also denotes molecularly disperse or colloidally
disperse solutions as well as dispersions of particles swollen in the
solvent.
Compounds designated as polycarbodiimides are those which have molecular
weights above 300 and contain at least two carbodiimide groups per
molecule.
Polycarbodiimides of this type are prepared, for example, by an
intermolecular elimination of CO.sub.2, preferably catalysed by compounds
which contain phospholine oxide groups (or phospholane oxides, sulphides
or imides, phospholine sulphides or phospholine imides), from
polyfunctional isocyanates and, if appropriate, monofunctional isocyanates
used conjointly. The so-called polycarbodiimides thus formed may also
contain in the molecule, in addition to carbodiimide groupings, yet
further reactive groups, for example isocyanate groups which may be
terminal, uretone groupings and groupings which can be formed by an
addition reaction of, for example, isocyanate or carbodiimide, and
possibly also CO.sub.2, with the carbodiimide groups in the chain. The
additional appearance of these groupings in the polycarbodiimide molecule
depends, in most cases, on the nature and the reaction conditions of the
isocyanate or isocyanate mixture utilised for the preparation of the
polycarbodiimide.
Since the polycarbodiimides which have been prepared, according to the
state of the art, on the basis of polyfunctional isocyanates and, if
appropriate, monofunctional isocyanates used conjointly for the purpose of
oligomerisaton, for example by catalysts with 0.1- 2% by weight of a
phospholine oxide, say 1-methyl-1-oxo-phospholine, whilst stirring at
10.degree.- 150.degree. C., can obviously contain terminal isocyanate
groups which are not fully reacted, it is advantageous, if appropriate, to
eliminate these terminal groups by adding compounds which react with
isocyanates. Advantageously, amines or alcohols are used for this purpose
and an additional lengthening of the polycarbodiimide component can be
achieved in the case that, for example, bifunctional amines or alcohols
are employed. Examples of compounds which can be used to eliminate the
isocyanate groups, or can be used as chain-stoppers, are water, ammonia,
primary and secondary aliphatic, cyclo-aliphatic and aromatic amines, such
as say methylamine, diethylamine, allylamine, cyclohexylamine,
benzylamine, aniline, toluidine, ditolylamine, toluylenediamine and
4,4'-diphenylmethanediamine, or especially primary and secondary alcohols,
such as methanol, ethanol, butanol, allyl alcohol, hydroxyethyl acrylate,
oleyl alcohol or phenol, polyethers, polyesters or polycarbonates with
lateral or terminal OH groups, ethylene glycol, propylene glycol,
butanediol, hexanediol, ethanolamine, diethanolamine, or triethanolamine.
In general, these compounds are added in amounts which are equivalent to
the residual isocyanate groups; however, for special purposes of
application, say adhesives, it is also of interest to use lesser amounts,
say 0.1- 0.8 equivalents, whilst larger added amounts are rarely
indicated since they frequently effect an undesired plasticisation of the
polymerisation products.
In many cases, however, the carbodiimidisation reaction can be carried out
up to complete conversion of the NCO groups so that the procedure
described above is superfluous.
Furthermore, it is frequently not necessary completely to remove small
residual isocyanate contents.
The polycarbodiimides being employed are preferably prepared by
carbodiimidising polyfunctional, preferably bifunctional, aliphatic,
araliphatic or especially aromatic isocyanates. A conjoint use of
monofunctional isocyanates or trifunctional and more highly functional
isocyanates as chain stoppers or branching agents for the
polycarbodiimides can be considered, in which case the amount of more than
bifunctional isocyanates should, however, be below 50 percent by weight,
preferably below 15 percent by weight, of the total amount of isocyanate,
whilst monofunctional isocyanates can, if appropriate, be used conjointly
even in amounts of up to 75% by weight, preferably up to 50% by weight, it
being possible to obtain polycarbodiimides of particularly low viscosity.
Polycarbodiimides in the sense of the invention can also be obtained by
polycarbodiimidising mixtures of trifunctional and/or more highly
functional isocyanates with monoisocyanates.
For example, the following isocyanates can be utilised for the desired
purpose: alkyl isocyanates, such as methyl, allyl, butyl and stearyl
isocyanate; alkyl diisocyanates, such as ethylene diisocyanate,
tetramethylene diisocyanate, hexamethylene diisocyanate and isophorone
diisocyanate, but preferably aromatic monofunctional or bifunctional
isocyanates, such as phenyl isocyanate, phenylene diisocyanates, the
isomeric toluylene diisocyanates, the isomeric diphenylmethane
diisocyanates, dimethyldiphenylmethane diisocyanates and technical
mixtures of diphenylmethane diisocyanates, which optionally can also
contain polynuclear diisocyanates or trifunctional isocyanates.
Preferably, the isocyanates which can be used are hexamethylene
diisocyanate, isophorone diisocyanate and especially the toluylene
diisocyanates and diphenylmethane diisocyanates. The isomers of toluylene
diisocyanate are here of particular interest. Phenyl isocyanate should be
particularly singled out as a chain stopper.
Those isocyanates can also be used which, according to the state of
isocyanate chemistry, are accessible from polyfunctional isocyanates by
trimerisation, formation of uretdiones, allophanatisation, biuretisation
or partial reaction with amines or alcohols.
In principle, it is thus also possible to use, or use conjointly, those
polyfunctional isocyanates which are formed by reacting excess
diisocyanate with monofunctional, bifunctional or polyfunctional compounds
carrying OH groups or NH groups and which can be encountered in industrial
polyurethane chemistry either under the name of modified isocyanate or
isocyanate prepolymer. The inclusion of such modified polyisocyanates into
the present process provides further scope for varying the process
depending on the choice of chain length or of the chemical nature of the
polyfunctional OH compounds and NH compounds, for example polyethers,
polycarbonates or polyesters.
The vinyl compounds which can be used are aliphatic or aromatic
polymerisable vinyl monomers. These include, for example, esters of vinyl
alcohol or esters of acrylic acid or methacrylic acid, such as vinyl
acetate, vinly propionate, vinyl benzoate or the methyl, ethyl, propyl,
(iso)-butyl or cyclohexyl esters or the glycol or glycerol esters of
acrylic acid and methacrylic acid, and also acrylonitrile and
methacrylonitrile, acrylic acid and methacrylic acid dialkylamides,
methylene-bis-acrylamide, maleic acid esters or fumaric acid esters,
maleic acid N-alkylamides, maleimides, vinyl pyrrolidone and vinyl
halides, such as vinyl chloride and vinylidene chloride, but in particular
vinyl aromatic compounds, such as isopropenylphenol and its esters or
ethers, .alpha.-methylstyrene, vinyltoluene, and p-chlorostyrene, but
above all styrene and/or divinylbenzene.
The only restriction on the amounts of polycarbodiimide and vinyl compounds
in the casting resin according to the invention is that these liquid
mixtures must be processable. For example, they must be capable of taking
up fillers, of penetrating fibre mats and of being cast; they must be
workable at least under pressure and heat. Accordingly, the vinyl monomer
preferably amounts to 0.1 to 95, more preferably 0.5- 70, % by weight of
the weight of the solution.
The casting resin according to the invention can be obtained, for example,
by dissolving preformed polycarbodiimides in vinyl monomers or,
preferably, by preparing the polycarbodiimides in situ in the vinyl
monomers.
The additional conjoint use of solvents is possible but not necessary.
The casting resins according to the invention can be cured at temperatures
between -25.degree. and +280.degree. C., preferably +10.degree. and
+180.degree. C., by polymerization initiated by UV light, ionising
radiation, for example X-ray radiation or nuclear radiation, or preferably
by free-radical initiators or initiator systems, which are customary in
practice and which can already be added, in full or in part, to the
casting resin during the preparation or immediately before the
polymerisation.
Examples of suitable initiators are organic peroxides, such as lauroyl
peroxide, dibenzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide,
di-t-butyl peroxide, dicumyl peroxide, cyclohexanone peroxide, t-butyl
peroctoate or combinations of such peroxides with reducing agents or
co-activators, such as, for example, boron alkyls, SO.sub.2 donors or
amines, for example p-dimethylaminotoluene or metal salts, such as cobalt
naphthenate. Azo compounds, such as azodiisobutyronitrile or
azodiisobutyric acid diethyl ester, are also outstandingly suitable.
Peroxides, such as t-butyl hydroperoxide, cumene hydroperoxide or t-butyl
peroctoate, prove to be particularly suitable.
The polymerisation initiators are used in amounts of 0.01 to 3%, preferably
0.1 to 1%, relative to the weight of the solution.
Frequently, an initiator is not required at all; simple heating or curing
of the casting resin at temperatures of above 40.degree. C. suffices. A
pre-curing at about 80.degree.C. with subsequent raising of the curing
temperatures to 120.degree.- 150.degree. C. has proved very advantageous.
However, the resins fully cured in this way can be heat-treated further at
even higher temperatures of about 200.degree.- 250.degree. C.
The conjoint use of phenol or of phenolic compounds, such as
4,4'-dihydroxy-diphenyl-dimethylmethane, did not impair the thermal
curing.
Surprisingly, curing can also be accelerated by compounds containing
readily saponifiable or hydrolysable halogen, preferably chlorine, such as
inorganic or organic acid chlorides (acetyl chloride, adipic acid
chloride, benzoyl chloride, chlorides of the benzenedicarboxylic acids,
that is to say phthaloyl chloride or terephthaloyl chloride, thionyl
chloride, BF.sub.3 or phosphorus oxychloride) or isocyanidedichlorides,
such as perchloroethyl isocyanide-dichloride and trichloroethyl
isocyanide-dichloride, it being possible in some cases to dispense with
radical-forming agents. These accelerators and classes of compounds are
preferably employed in amounts from 0.01 to 50, preferably 0.3 to 10, % by
weight at temperatures between 20.degree. and 250.degree. C., preferably
80.degree. to 180.degree. C.
It is possible to combine different curing processes. Preferably, curing is
carried out by means of heat (very low content of foreign substances); the
conjoint use of, for example, halogen compounds of phosphorus gives
products with an improved behaviour in fire; the combination of free
radical-forming agents with the halogen compounds gives polymerisation
products which have particularly few bubbles.
Since a considerable amount of heat of polymerisation can be liberated
during curing, and also in order to adapt the shrinkage and the mechanical
properties to the desired application, it is often advantageous to add
fillers, for example in a pulverulent form or in the form of fibres,
acicular crystals, flakes, balls or small hollow bodies. Examples of
suitable fillers are chalk, calcium oxide, calcium hydroxide, hydrated
aluminium oxide, quartz powder, glass beads, talc, graphite, types of
carbon black, polymer powders, for example based on polyethylene,
polypropylene, polymethyl methacrylate, polystyrene or polyvinyl acetate,
glass fibres. potassium titanate, gypsum fibres, carbon fibres, steel
fibres, metal powders, small gas bubbles, droplets of water, hollow glass
beads and the like. Amounts of up to 300%, relative to the weight of the
solution, of these fillers can be employed. Dyestuffs and making-up
auxiliaries (emulsifiers, thickeners and odoriferous substances) can be
incorporated, as can flame-proofing agents, for example those based on
phosphorus or antimony
The casting resins can also be combined with other resins, for example with
epoxide resins, unsaturated polyester resins, maleimide resins, cyanate
resins, isocyanate resins and alkyd resins. The other resins can be used
conjointly in amounts of 0- 95% by weight, preferably in amounts of less
than 50% by weight.
The casting resins can be processed in the same way as unsaturated
polyester resins, that is to say, for example, by casting, spreading, as a
laminate with glass fibres (glass mats) and other reinforcing materials,
as a prepreg or as a compression moulding composition, transfer moulding
composition or foam or foamed binder for lightweight concretes.
The casting resins can be used for preparing mouldings and coatings of
carriers for electronic circuit elements, insulators and casting
compositions and for preparing foamed components, hollow bodies and heat
shields, or impregnating wood, cardboard, textiles and non-wovens or as a
binder for organic-inorganic concretes. They can also be used as an
adhesive.
Curing can also be carried out in several stages, for example in accordance
with the prepreg technique in which pre-cured semi-finished articles can
be fully cured, whilst being finally shaped.
It is also possible to granulate material which has been pre-cured at
temperatures of, for example, below 120.degree. C. and subsequently to
subject it to compression moulding at an increased temperature, for
example 200.degree. C., to give mouldings.
The parts indicated in the examples are parts by weight.
EXAMPLE 1
280 parts of a technical mixture of toluylene diisocyanate isomers, which
contains approximately 80% of the 2,4-isomer, are stirred at 120.degree.
C. for 1 hour with 120 parts of styrene and 15 parts of allyl alcohol as
well as 1 part of 1-methyl-1-oxo-phospholine. Thereafter, free isocyanate
can no longer be detected by amine titration in the reaction mixture. The
mixture is cooled rapidly and a liquid product solution is obtained.
100 parts of this solution are stirred with 0.8 part of cumene
hydroperoxide. 5 parts of benzoyl chloride are then also added and the
mixture is cast in a cylindrical mould. The latter is cured at 120.degree.
C. in a heating cabinet in the course of about 4 hours. A brownish clear
polymer block which is subsequently after-cured for about 2 hours at
200.degree. C., is obtained.
The material does not distort and is hard at 200.degree. C.
EXAMPLE 2
0.8% by weight of phosphorus oxychloride is stirred into the casting resin
solution obtained in Example 1. The composition cures in the course of 4
hours at 80.degree. C. in a cylindrical mould. It is heat-treated further
at 150.degree. C. A brown clear polymer block which does not distort and
is hard, even at 200.degree. C., is obtained.
The fact, demonstrated in Example 1 and 2, and also in some examples which
follow, that polymer blocks of clear appearance are obtained, indicates
that no isolated significant amounts of polystyrene are contained in the
reaction product. The addition of polystyrene, dissolved in styrene, or of
polystyrene powder leads to milky-turbid polymerisation products,
presumably because of incompatibility.
EXAMPLE 3
250 parts of 4,4'-diphenylmethane diisocyanate, 107 parts of styrene, 30
parts of phenyl isocyanate and 4.5 parts of 1-methyl-1-oxo-phospholine are
stirred at 120.degree. C. for 30 minutes, the formation of
polycarbodiimide taking place with elimination of CO.sub.2. 0.5 part of
t-butyl hydroperoxide and 0.5 part of POCl.sub.3 are then stirred, at
65.degree. C., into a partial amount of 100 parts of the reaction product.
A non-woven of glass fibre is impregnated with the material and cured in a
press at 205.degree. C. for 5 minutes. A clear sheet which retains its
rigid character, even at 200.degree. C., is obtained.
EXAMPLE 4
280 parts of the isocyanate mixture used in Example 1, 70 parts of
divinylbenzene, 50 parts of styrene, 30 parts of phenyl isocyanate and 1
part of 1-methyl-1-oxo-phospholine are stirred at 120.degree. C. for 45
minutes. Free isocyanate is then no longer detectable by titrimetry in the
reaction solution. The reaction product is cooled and processed as
follows:
(a) 100 parts filled into a cylindrical mould and cured at 120.degree. C.
in the course of 5 hours. The cylinder can be after-cured at 200.degree.
C. without significant change of its dimensions. It has a clear
appearance.
(b) A non-woven of glass is impregnated with the reaction solution. This
non-woven is cured at 45.degree. C. Subsequently the prepreg which has
been impregnated in this way and is not tacky, is fully cured in a press
at 200.degree. C., whilst being shaped.
(c) 1 part of t-butyl peroctoate is added to 100 parts and the mixture is
cured in the cylindrical mould for 1 hour at 80.degree. C., 1 hour at
120.degree. C. and fully at 200.degree. C. A polymer moulding results
which is hard even at 200.degree. C.
(d) The procedure followed is as in (c) but 1 part of POCl.sub.3 is
employed in place of the peroxide. A clear brownish polymer moulding is
formed.
(e) 100 parts of the reaction product are cured at 80.degree. C. for 12
hours. The cured product is subsequently granulated.
The granules obtained are compression-moulded in a press at 250.degree. C.
in the course of 5 minutes, to give a sheet. The sheet has a homogeneous
character.
EXAMPLE 5
200 parts of the toluylene diisocyanate used in Example 1, 200 parts of
phenyl isocyanate and 4.6 parts of 1-methyl-1-oxo-phospholine are stirred
at 120.degree. C. for 45 minutes; with elimination of CO.sub.2, a
polycarbodiimide is formed in which isocyanate is no longer detected by
titration. The reaction product represents a brownish honey-like liquid.
(a) The reaction product is filled into a cylindrical mould, stirred with
5% by weight of styrene and, after the addition of 0.5% by weight of
di-t-butyl peroxide, cured at 140.degree. C. for 12 hours. A hard polymer
moulding is formed.
(b) The reaction product is stirred with 30% by weight of diallyl phthalate
and 1% by weight of dicumyl peroxide and is cured in a cylindrical mould
at 120.degree. C. for 10 hours and at 150.degree. C. for 5 hours. A hard
polymer moulding is formed.
(c) The reaction product is stirred with 50% by weight of a commercially
available unsaturated polyester resin, present as a solution in styrene,
and with 1% by weight of benzoyl peroxide, and is cured in a cylindrical
mould for 3 hours at 120, 3 hours at 140 and 3 hours at 160.degree. C. A
homogeneous hard prepolymer moulding is formed.
(d) The reaction product is mixed at 80.degree. C. with 50% by weight of
4,4'-diphenyl-dimethylmethane diglycidyl ether, then filled into a
cylindrical mould and cured for 3 hours at 120 and 10 hours at 150.degree.
C. A hard polymer moulding is formed.
The % contents indicated relate to the reaction product employed.
EXAMPLE 6
200 parts of the isocyanate used in Example 1, 200 parts of phenyl
isocyanate, 172 parts of styrene and 4.6 parts of
1-methyl-1-oxo-phospholine are stirred at 120.degree. C. for 45 minutes.
Thereafter, isocyanate groups are no longer detectable by titration in the
reaction product.
100 parts of the reaction product are filled into a cylindrical mould and
cured at 120.degree. C. for 8 hours. The hard moulding formed is then
heat-treated at 200.degree. C. for 5 hours, no visible change in shape
being observable but merely a dark coloration.
EXAMPLE 7
300 parts of the isocyanate used in Example 1, 100 parts of styrene, 72
parts of divinylbenzene, 100 parts of phenyl isocyanate and 4.5 parts of
1-methyl-1-oxo-phospholine are stirred at 120.degree. C. for 45 minutes.
The reaction product formed is provided in various batches with the
following additives:
(a) without additive
(b) 10% by weight of limonene
(c) 1% by weight of cumene hydroperoxide
(d) 1% by weight of phosphorus oxychloride
(e) 1% by weight of cumene hydroperoxide 1% by weight of benzoyl chloride
(f) 3% by weight of thionyl chloride
(g) 1% by weight of perchloroethyl isocyanide-dichloride.
A volume of 60 ml is then filled into a cylindrical mould and cured at
120.degree. C. for 8 hours. In all cases, a hard polymer moulding is
formed which retains its shape, even without formation of bubbles, when it
is subsequently heat-treated treated for 4 hours at 200.degree. C. in a
circulating air cabinet.
The same results are obtained by employing a reaction product which is
obtained when 200 parts by weight of a commercially available technical
liquid isocyanate mixture (which is obtained by phosgenation of
aniline/formaldehyde condensation products), 200 parts by weight of phenyl
isocyanate, 100 parts by weight of styrene, 72 parts by weight of
divinylbenzene and 4 parts by weight of 1-methyl-1-oxo-phospholine are
stirred at 120.degree. C. for 45 minutes and then rapidly cooled.
* * * * *
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Description |
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