Note: Descriptions are shown in the official language in which they were submitted.
BAYER AKTIENGESELLSCHAFT 5090 Leverkusen, Bayerwerk
~onzernverwaltung RP
Patente Konzern Wr/by-c
Rrocess for the preparation of plastics, including sheet-
like structures
The invention relates to a process for the preparation of
plastics by heat-curing of selected polyesters containing
(methlacryloyl groups.
Polyesters carrying (meth)acryloyl groups are known. So-
called polyesteracrylates of this type, which, asdescribed in, for example, German Offenlegungsschrift
2,838,619, 2,261,612, 3,316,593, 1,~17,788, 2,033,769,
2,053,683 and 2,423,354, are obtained as reaction
products of (meth)acrylic acid with diols, polyols and
dicarboxylic acids, ~enerally undergo crosslinking by
rneans of electron beams or UV radiation. Special
apparatuses are necessary for this purpose. In UV
curing, the only areas cured are those which lie in the
irradiation area of the UV lamps.
Curing by means of free radical formers, such as
peroxides, which are cleaved by heat and/or accelerators,
is normally carried out only in the absence of air, since
it is otherwise impossible to obtain non-tacky and/or
scratch-resistant and solvent-resistant plastics, in
particular surfaces.
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It was therefore the o~ject of the invention to providea novel process for the preparation of plastics,
including sheet-like structures, from polyesters
containing (meth)acryloyl groups, in which curing of the
unsaturated polyesters is possible in the presence of
atmospheric oxygen by a thermal method, optionally with
the concomitant use of siccatives and of
~hydro)peroxides.
This object was achieved by providing the process
: 10 according to the invention, described in detail below.
In the process according to the invention, polyesters
which contain special (meth)acryloyl groups and which
surprisingly are heat-cura~le even in the presence of
atmospheric oxygen are used.
15 The invention relates to a process for the preparation of
plastics, including sheet-like structures, by curing
polyesters containing (meth)acryloyl groups, or mixtures
thereof with other plastics precursors containing
(meth)acryloyl groups, which polyesters or mixtures have
been shaped, optionally as a mixture with inert
auxiliaries and additives and/or with copolymerizable
monomers and/or optionally dissolved in inert solvents or
optionally emulsified in water, characterised in that the
polyesters which contain (meth)acryloyl groups and which
are used are those which have been prepared from
A) 0.4 to l.O.mol of an unsaturated dicarboxylic acid
component, consisting of maleic acid, maleic
anhydride, fumaric acid, tetrahydrophthalic acid,
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tetrahydrophthalicanhydride,norbornenedicarboxylic
acid and~or norbornenedicarboxylic anhydride,
B) to 0.6 mol of another dicarboxylic acid component,
~onsisting of at least one aromatic or saturated
(cyclo)aliphatic dicarboxylic acid of the molecular
weight range 100 to 202 and/or at least one
anhydride of such a dicarboxylic acid,
C) 0.3 to 2.0 mol of at least one ether-alcohol
component, consistinq of at least one monovalent,
divalent, trivalent or tetravalent ether-alcohol
which has at least one ethylene oxide unit -CH2-CH2-
O- as part of an ether structure and is of the
molecular weight range 92 to lO00,
D) 0 to 1.7 mol of another alcohol component,
consisting of at least one monohydric, dihydric,
trihydric or tetrahydric alcohol which has a
molecular weight of 46 to 500 and has no ethylene
oxide units as part of an ether structure and
E) 0.5 to 6.0 mol of an unsaturated monocarboxylic acid
component, consisting of acrylic acid and/or
methacrylic acid,
with the proviso that the sum of the moles of components
A) and B) is 1.0, the sum of the hydroxyl equivalents of
components C) and D) at least corresponds to the sum of
the carboxyl equivalents of components A), B) and E), the
content of olef ~ c double bonds (calculated as =C=C-,
molecular weight = 24) in the polyesters is 5 to 17% by
weight and the acid number of the polyester is 0 to 50,
and
curing of the polyester is carried out in the presence of
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atmospheric oxygen at temperatures above 80 C.
In the preparation of the polyesters,
0.5 to 1.0 mol of component A),
0 to 0.5 mol of component B),
0.5 to 2.0 mol of component C),
0 to 1.6 mol of component D) and
1.0 to 4.0 ~ol of component E)
are preferably used, the double bond content (calculated
as =C=C=, molecular weight = 24) of the polyester
preferably being 6.S to 15% by weight and the acid number
of the polyester preferably being 0 to 40. The above
data with regard to the acid number are based on mg of
KOH/g of substance.
Component A) is preferably maleic anhydride or
lS tetrahydrophthalic anhydride. Component B) is, for
example, an acid, such as phthalic ac.id,
hexahydrophthalic acid, isophthalic acid, terephthalic
acid or adipic acid, or phthalic anhydride or
hexahydrophthalic anhydride.
Component C) comprises monohydric, dihydric, trihydric or
tetrahydric alcohols which have ether groups, preferably
have a molecular weight of 106 to 800 and contain at
least one ethylene oxide unit -CH2-CH2-O- as part of an
ether structure. Ether alcohols of this type are
obtained by ethoxylation of suitable initiator molecules
in a manner known per se. Suitable initiator molecules
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are, in particular, the monohydric or polyhydric alcohols
which correspond to the ether-alcohols and are free of
ether groups. The ether-alcohols used as component C)
generally have a degree of ethoxylation of 1 to 10,
preferably 1 to 8, ~he degree of ethoxylation specifying
the average number of moles of ethylene oxide which have
undergone an addition reaction with 1 mole of an alcohol
used as the initiator molecule. Ethoxylated diols or
triols having a degree of ethoxylation of 1 to 6 and a
molecular weight of 106 to 398 are particularly
preferably used as component C).
.
Component D) comprises any monohydric or polyhydric,
preferably dihydric to tetrahydric, alcohols which do not
have any ethylene oxide units as part of an ether
structure. The molecular weight of these alcohols is
preferably 46 to 500. For example, n-hexanol,
isooctanol, benzyl alcohol, ethylene glycol, propylene
glycol, propane-1,3-diol, the isomeric butanediols,
pentanediols, hexanediols or dimethylolcyclohexanes,
~0 trimethylolpropane, propoxylated trimethylolpropane
; and/or pentaerythritol are suitable.
For the preparation of the polyesters containing
(meth)acryloyl groups, either all constituents A to E are
heated together in an inert solvent under the conditions
of an azeotropic esterification reaction until no further
water separates off, or an OH-containing polyester is
first prepared from the components A to D and this
polyester is then allowed to react with (meth)acrylic
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acid under azeotropic esterification conditions in an
inert solvent until no further water separates off, or a
polyester containing COOH groups is first prepared from
components A and B and part of components C and/or D and
S the remaining components are then allowed to react with
the polyester under azeotropic esterification conditions
in an inert solvent until no further water separates off.
In all cases ! the solvent is removed by distillation
after the reaction. If necessary, aftertreatment of the
end product can be carried out to obtain a lower acid
number, for example the reaction with carbodiimides
according to German Offenlegungsschrift 3,514,402 or with
epoxides according to German Offenlegungsschrift
3,316,593.
The azeotropic esterification conditions used for the
preparation of the polyester (meth)acrylates are the
traditional conditions, that is to say an esterification
catalyst, for example sulphuric acid or p-
toluenesulphonic acid, is used and the reactants are
heated in the presence of one or more inhibitors, such as
hydroquinone monomethyl ether, and atmospheric oxygen (to
prevent premature polymerization) in an inert solvent,
such as cyclohexane, isooctane or toluene, and the water
of reaction formed is removed from tha system. In
general, the preparation of the polyesters is carried out
within the temperature range from 70 to 130~C.
~he polyesters containing ~meth)acryloyl groups and
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ob~ained in this manner are in general liquid products
which have a viscosity of about 1 to 100 Pa.s at 23C.
Conversion of the unsaturated polyesters, which are
; plastics precursors, into cured plastics is carried out
in general after a shaping procedure.
The term "plastics~ is intended to embrace any three-
dimensional, cured shaped articles as well as cured
cement or filling compounds or sheet-like structures, in
particular cured surface coatings. Accordingly, the term
"shaping" is intended to include, inter alia, the
production of sheet-like structures, for example of
surface coatings or the processing of cements or filling
compounds.
Depending on the intended use and depending on the
viscosity, the polyesters containing (meth)acryloyl
groups can be mixed with very different types of inert
auxiliaries and additives prior to shaping. These
include fillers, pigments, dyes, thixotropic agents,
smoothing agents, flatting agents and levelling agents,
which can be used in customary amounts. Particularly for
the production of surface coa~ings, the polyesters
containing (meth)acryloyi groups can a~so be used as a
solution in coating solvents known per se, as a mixture
with copolymerizable monomers or as an emulsion in water.
2~ Suitable solvents are, for example, butyl acetate,
cyclohexane, acetone, toluene or mixtures of such
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solvents.
Examples of suitable copolymerizable monomers are organic
compounds which have at least one copolymerizable
olefinic double bond per molecule and have a viscosity of
not more than 500 mPa.s at 23C. These include, for
example, styrene, hexane-1,6-diol diacrylate,
trimethylolpropane triacrylate and N-vinylpyrrolidone.
The inert solvents and also the copolymerizable monomers
can each be used in amounts of up to 100% by weight,
preferably up to 50% by weight, relative to the weight of
th~ polyesters containing (meth~acryloyl groups.
It is also possible simultaneously to use both inert
; solvents of the type stated by way of example and
copolymerizable monomers of the type stated by way of
Example.
It is also possible for the polyesters containing
(meth)acryloyl groups to be mixed with other plastics
precursors containing (meth)acryloyl groups, in
particular urethane (meth)acrylates, prior to curing.
These plastics precursors, which are optionally used,
generally have a viscosity of more than 10000 mPa.s at
23 C. These additives can be used in amounts of up to
200% by weight, preferably up to 100% by weight, relative
to the weight of the polyesters containing (meth)acryloyl
groups.
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If the polyesters containing (meth)acryloyl groups are to
be processed from aqueous emulsion, the preparation of
corresponding aqueous emulsions can be carried out, for
example, with the aid of external emulsifiers and,
optionally, customary auxiliaries used in emulsion
technology.
Emulsifiers which are suitable for this purpose are known
and are described, for example, in Ullmanns Encyclopadie
der techn. Chemie [Ullmanns Encyclopaedia of Industrial
Chemistry], Vol. 10, 4th Edition, Chapter on Emulsions,
page 449 et seq.
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Preferred emulsifiers are copolymeri~able polyester
emulsifiers containing (meth)acryloyl groups, as
described in German Offenlegungsschrift 3,241,264.
The aqueous emulsions contain in general from 10 to 70~
by weight, preferably 30 to 70% by weight, of the
polyesters which contain (meth)acryloyl groups and are an
essential feature of the invention. The preparation of
the emulsions can be carried out by stirring water into
the mixture of the polyester (meth)acrylate according to
the invention and the emulsifier, for example simply by
stirring or by means of a dissolver.
To form a finely divided emulsion, that is to say for
better application of the gravitational forces, the
addition of water in portions at te~peratures below 30C
is advantageous. With optimal shearing, oil-in-water
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emulsions are formed.
In all variants of the process according to the
invention, curing is effected, optionally after
evaporation of volatile auxiliaries, such as inert
solvents or water, by a heat treatment at above B0 C. In
a preferred embodiment, curing is assisted ~y the
addition of polymerization initiators and of siccatives
of the type known per se. Where such auxiliaries are
present, curing temperatures of 80 to 160C, preferably
90 to 150C, are generally sufflcient.
; Suitable polymerization initiators are, in particular,
(hydro)peroxides of the type known per se, such as tert-
butyl perbenzoate, benzoyl peroxide, cyclohexanone
peroxide, methyl ethyl ketone peroxide, acetylacetone
peroxide, tert-butyl per-2-ethylhe~anoate, bis-(4-tert
butylcyclohexyl) peroxydicarbonate, tert-butyl
hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane
2,5-hydroperoxide and diisopropylbenzene
monohydroperoxide. These (hydro)peroxides are preferably
used in amounts of 0.~ to 3% by weight relative to the
weight of the polyesters containing (meth)acryloyl
groups.
The siccatives used in addition to the polymerisation
initiators mentioned as examples are likewise those of
` 25 the type known per se, such as, for example, cobalt
: salts, lead salts and manganese salts of acids soch as
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linseed oil fatty acids, tallow oil fatty acids and soya
bean oil fatty acids, of resin acids, such as abietic
acid and naphthenic acid, or of acetic acid and
isooctanoic acid. They are used in the form of organic
solutions in amounts such that the metal content is 0.001
to 0.1% by weight, rela~ive to the weight of the
polyesters containing (meth)acryloyl groups.
If polymerization initiators and siccatives are not
concomitantly used, the temperature of the curing
procedure according to the invention is in general at
least 150 C, preferably 150 to 190 C. However, it is of
course also possible on the one hand to use
polymerization initiators and siccatives of the type
stated by way of example and on the other hand
nevertheless to employ the last-mentioned high
temperatures in order to achieve accelerated curing.
In the Examples which follow, all percentages are based
on weight.
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ExamPles
In the Preparation Examples 1 to 5 according to the
invention and Comparative Examples 6 and 7, summarised in
the Table below, the starting components A), B) and D)
are first heated to 150 - 185C for 6 hours under
nitrog~en in the absence of other additives in the first
stage in each case.
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The procedure for the second stage of the process
according to the invention was carried out in each case
in 60% strength solution in cyclohexane in the presence
of 1.5~ of p-toluenesulphonic acid as a catalyst and of
0.3% of p-methoxyphenol as an inhibitor, rela~ive in each
case to the sum of the components A) to E~. After the
addition of components C) and E) and catalysts and
inhibitors in cyclohexane, the mixture is heated at 80 to
; 100C while passing through air, until no further water
separates off. After the mixture has cooled, the solvent
is distilled off in vacuo at S0 to 90C.
.
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Use Examples_l_to 5 ~according to the invention) and
6 and 7 (Comparative Examples)
1.5% of tert-butyl perbenzoate and 1% of cobalt octoate
(2.2% metal content) are added to the products of the
above Examples 1 to 7~ After the coating films have been
applied to glass sheets, they are heated for 30 minutes
at 130C. The resulting, dry coating films have a
thickness of about 100 ym.
The film properties obtained are shown in Table 2.
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Apart from Comparative Examples 6 and 7, the surfaces of
the coating ~ilms can be scratched only with difficulty,
if at all.
While both hard and solvent-resistant coatings are formed
with the products accordin~ to the invention, of Examples
l to 5, the products of Comparative Examples 6 and 7 do
not have adequate properties.
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