Note: Descriptions are shown in the official language in which they were submitted.
YO-YO I
Toe prevent invention is concerned with a
hardier for epoxide resin masse bayed on dicyandiamide~
It it Noel to use dicyandiam:ide for the harden-
in of epoxide resins of US. Patent Specification
owe. 2,637,715 and 3,391,113). The advantages of the
dicyandiamide are, in particular, its toxicological
harmlessness and the absence of smell, as well as its
chemically inert behaviGur, so that the resin-hardner
mixture ha a good storage-stability.
The disadvantages of dicyandiamide are its poor
volubility and the non-optimal distributability of the
hardier in the epoxide resin which, for example, can
lead to an increased consumption of hardier. However,
this increased amount used give rise, in turn, to
the effect that the-haxdened resin-can contain regions
with a high content-of non-consumed-hardner and thus -
can have defects in end product
Attempts have not been lacking to improve this
problem of the poor di3~ributability in liquid epoxide
resins or in epoxide resins melting at a higher-temp-
erasure Depending upon the intended use, the follow-
in ways have been employed
thy use ox an appropriate solvent-or solvent mixture
for the production of impregnation solutions from
epoxide resin and hardier (cf. Federal Republic of
Germany Patent Specification No. 30 26 706 and Gunman
Democratic Republic Patent-Specification owe 133 955),
.
~2~3~33~
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the use of substituted dicyandiamides with improved
distributability in epoxide resin masses (cf., for
example, French Patent Specification No. 22 07 911),
and
the use of dicyandiamide dispersions in liquid
epoxide resin mixtures.
Whereas, according to the firs way, only a few
solvent mixtures could be found which display the
necessary criteria, such a good volubility or good
compatibility with the epoxide resin mixtures, in the
case of the second way, the provision of substituted
dicyandiamides is uneconomical because the production
of these products gives rise to high operational and
investment costs, In the cave of the last-mentioned
way, the difficulty arise that dicyandiamide must be
used which is as finely divided as pro sidle in order
to achieve a good distribution in powdered epoxide
resin-hardner mixture or to obtain dispersions in
liquid epoxide resin mixtures and, on the other hand,
finely-divided dicyandiamide has a marked tendency to
cake so that finely-divided dicyandiamide forms
agglomerates within a very short space of time which
also can scarcely be broken up again by grinding. In
the case of dicyandiamide suspensions, this agglomer-
anion of finely-ground dicyandiamide leads to the
formation of comparatively large flock, which give
rise to considerable problems in the epoxide resin
,,
mixtures.
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Therefore, it is an object of the present
invention to provide a hardier for epoxide Ryan
masse based on dicyandiamide which does not display
the above-mentioned known disadvantages, which is
characterized by good application-technical properties
and which can be produced economically.
Thus, according to the present invention, where
is provided a hardier for epoxide resin masses based
on dicyandiamide, wherein it contains
a) dicyandiamide with a particle size off 90% 10 us
and
by 0.1 to OWE by weight of silicon dioxide and/or of
an oxide of a metal of Group IDA or IT of the
Periodic Table with a large specific surface area
Surprisingly, we have found that the hardier
according to the-present invention for epoxide resin
masse has an improved distributability in the oxide
resin, as well as an increased storage stability in
the epoxide resin-hardner dispersions.--- Furthermore,
the addition of silicon dioxide and/or of oxides of
metal of Group IDA or JIB of the Periodic Table bring
about a sometime considerable shortening of the gel
times in comparison with normal dicyandiamide, which
was also not foreseeable.
The epoxide resin hardier according to the
present invention based on dicyandiamide consists of
a dicyandiamide with a particle it I 90% I 10 em. J
~L~2~339
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a well a silicon dioxide and/or an oxide of a metal
of Group IDA or JIB of the Periodic Table with a
large specific surface area the specific surface area
preferably being at least 50 m2/gO according to BET,
in order to achieve the action according o the
present invention. Types of silicon dioxide which
are commercially available under the trade awry
Aerosol degas), a well a HDK (Weaker), have
proved to be especially advantageous.
Especially preferred oxides of metals of
Group IDA and JIB of the Periodic Table include
magnesium oxide, as well as mixture thereof but,
in principle, other oxides, for example those of
barium or of strontium, can alto be used.
The amount of the silicon dioxide or of the
oxide of a metal of Group IT or JIB of the Periodic
able is 0.1 to 3~/0 by weight and preferably from 0.2
to owe by weight referred to the weight of the
dicyandiamide.
The production of the epoxide resin hardier
according to the present invention preferably takes
place by continuously dosing the silicon dioxide
and/or the oxide of a metal of Group IT or JIB of
the Periodic Table to the dicyandiamide before
grinding to the desired grain give so that the metal
oxides have the same particle size distribution as the
dicyandiamide.
This prevents the finely-ground dicyandiamide
from clumping together immediately after the grinding
procedure, which would result in the formation of
undesired agglomerates. Thus, the mixing of the
components can be completed in one step The grinding
of the dicyandiamide and/or of the metal oxide can by
carried out without problems in conventional technical
devices, such as grader mills or the like, i.e. without
separation of dicyandiamide and of the metal oxides
during the grinding process
The dicyandiamide-containing epoxide hardier
according to the present invention, which has a bulk
density of 300 to 500 gloater, can be optimally
distributed in solid or liquid epoxide resins, it
thereby being possible to reduce the amount of
hardier in comparison with conventional hardness
based on dicyandiamide. We have found that amounts
I- of 3 to 6% by weight, referred to the epoxide equip -
valet weight, are sufficient.
The hardening reaction with the hardier accord-
in to the present invention can be additionally
activated with conventional hardening accelerators,
for example 2-methylimidazole, substituted urea
~monouron, Doreen), dimethylbenzylamine or substituted
methylenedianilines. The hardened epoxide resin has a
clearly improved chemical resistance and adhesion in
comparison with products produced with conventional
J
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dicyandiamide-containing hardeners
The following Examples are given for the purpose
of illustrating the present invention. For comparison
purpose, epoxide resin hardness Bud on dicyandiamide
are produced by grinding dicyandiam:ide with the follow-
in additives and compared with one another:
hardier a): dicyandiamide with 1.3% by weight silicon
dioxide HDK 20 with a specific surface
area of 200 mug (Weaker)
hardier I): ~icyandiamide with owe by weight
calcium oxide
hardier c): dicyandiamide with 0.8% by weight magnesium
oxide
hardier d): dicyandiamide with I by weight zinc
oxide
hardier en dicyandiamide without addition
Example 1.
of yo-yo air
hardier a): 4 - 5 my little agglomeration)
hardier boo 4 _ 5 em. (scarcely any agglomeration)
hardier c): 4 - 5 em. (scarcely any agglomeration)
hardier do: 4 - 5 em. (scarcely any agglomeration)
; hardier of: lo em. (agglomerates up to 40 my
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For the wet sieving, there it produced a 15%
suspension of the qualities obtained in ethyl acetate
saturated with dicyandiamide. Err homogeneous mixing
the suspension is treated for 5 minutes in an ultra-
sonic bath and then filtered through a vibrating previously weighed out filter with a mesh size of
10 em.
After the filter ha been rewashed Whitehall
further 50 go ethyl acetate, it is dried and reweighed.
From this is given the percentage content of Dyson-
doomed with a grain diameter of lest than 10 em.
hardier a: 99% 10 em.
hardier b): 98% 10 my
hardier c): 98% 10 em.
hardier d): 98% 10 em.
hardier en: 45% C 10 em.
. . .--
The gel times of various epoxide hardness accord-
in to the present invention are determined with
Epikote 1007 and compared with conventional Dyson-
doomed with an average particle size of 80 em,
~2~3~
Jo
hardier (owe by woo dicyandiamide gel time at 180C.
rev to Epikot~ 1007) in min.
dicyandiamide ~80 my 7.0
epoxide resin h~rdner a 6.0
5 epoxide resin hardier b) 5.0
epoxide resin hardier c) 6.0
epoxide resin hardier d) 5.0
dicyandiamide (80 m.) 3 0
0.25% 2-~ethylimidazole
10 epoxide resin hardier a) 2.5
0.25% 2-methyli~idazole
. . ,, _ __
Dispersions are produced each of 4% of the
hardier according to the present invention in Epikote
828 and compared with a dispersion of 4% dicyandiamide
(80 em.) within a period of time of 4 weeks:
____
hardier dispersion after 4 weeks
: storage
_____
dicyandiamide (80 em) almost all the material
deposited
hardier a) stable dispersion
hardier b) stable dispersion
hardier c) stable dispersion
25 hardier d) stable dispersion
hardier e) about 5~/0 deposited as flocks
2Z9~
Jo --10--
.
The dispersions described in Example 4 are
applied in the form of a lacquer layer to a cleaned
steel sheet and hardened at 180C. for one hour, the
S following observations thereby being made:
dicyandiamide (80 my): punctuate coating with unused
hardier, not completely
hardened
hardier ago smooth, transparent coating
10 hardier b): smooth, white-pigmented coating
hardier c): smooth, almost transparent
coating
hardier d): smooth, slightly pigmented
coating
15 hardier e): uneven, slightly punctuate
coating with unused h~rdner
,
