Note: Descriptions are shown in the official language in which they were submitted.
3~3
-2-
Condensation ~roduct and its use
In the foundry field increasing importance is attached
to binder systems based on polyurethane and which are the
reaction product of a cross-linkable, reactive OH group-
containing phenol resin and a polyisocyanate which serves as
the croEs-linking agent because, as a function of the harden-
ing catalyst used they can be cured within ~ery short times
(e.gO of less than one minute) at normal ambient temperature
and give good strength values. An example for a usable
process requiring such binders is the cold box process for the
production of foundry moulds and cores. In this process a
moulding composition comprising a foundry sand, the phenol
resin and the polyisocyanate (both of which are normally dis-
solved in an organic solvent) is moulded e.g. by means of an
"ejecting machine" and the moulded article is then hardened
by subsequent treatment with a tertiary amine which is either
gaseous or disper~ed in a carrier gas, which serves as the
catalyst. ~owever, polyurethane-based binder systems can
also be processed in other ways, For example the proced-
ure can be such that the hardening catalyst is added to themoulding composition in the form of a liquid amine before
moulding. In addition, hardening catalysts other than
amines can be used.
Phenol resins suitable for foundry binder systems
having a polyurethane base are substantially anhydrous and
must be such that under the action of the hardening catalyst
they ca~ rapidly react with the polyisocyanates, lead to good
11';~3~3
--3--
initial strengths of the moulded articles and achieve optimum
final stren~ths arter the storage Or said articles. Further-
more they should have a high linear structure and therefore a
low ~iscosity in order to aid the ~low beha~iour Or the mould-
ing composition. They must also be as stable as possible
in the dissolved state, i.e. their solutions must not have any
demixing tendancy. Examples of phenol resins of this type
which have been used under practical conditions are deecribed
in DAS 1583521~ 1720204 and 1920759. These known phenol
resin types are produced by condensing a phenol component with
an aldehyde, pre~erably rormaldehyde, condensation being car-
ried out in such a way that so-called ~'ben2yl ether-phenol
resins`' are obtained. This term is understood to mean
phenol resins with a content of terminal methylol groups in
which the individual phenol rings are mainly interlinke~ in a
linear o-o~ linkage, but optionally also in an o-p linkage
and in part via methylene bridges and in part via methylene-
ether bridges. The phenol component is the unsubstitute~
phenol or a substituted phenol in ~vhich at least both o-
position& are unoccupied.
However, these known phenol resin types fail to com-
pletely satisfactorily ~ulfill practical requirements. Thus,
although they can be cured e.g. with the moulding compos1tion
at ambient temperature, this cannot take place sufficiently
rapidly whilst gi~ing adequate initial strengths at lower
temperatures and certainly not at the not inrrequently occur-
ring temperatures down to 0 C or lower. However, the
decisive disad~antage o~ the known phenol resin tyes is that
1 1~1 !393
they cannot be dissolved in non-polar solvents and
instead require polar solvents. However, as polyiso-
syanates have a poor compatibility with polar solvents,
but a good compatibility with non-polar and preferably
aromatic solvents a mixture of non-polar and polar
solvents must be used as a compromise for the moulding
composition. This leads to a relatively short pro-
cessing time of the moulding composition (this is the
"life" during which-a completely mixed moulding com-
position remains storable and can be processed to
moulded articles having an adequate strength) obviously
because cross-linking reactions are initiated by the
proportion of polar solvents. In addition, many of
the readily available polar solvents such as e.g.
isophGrone or ethyl-isoamylketone have a very intense
smell or are even toxic, whilst attention must also
be paid to the compatibility of the solvent mixture
constituents, which greatly reduces the selection of
possible solvents.
The object of the present invention is to
provide a phenol re in intended for polyurethane-based
binder systems which fulfills the practical require-
ments of the foundry art in that it can be used at
lower temperatures of down to 0C., and lower in
exactly the same way as at ambient temperature,
- ~a 11 70393
whilst leading to moulding compositions having a very
long processing time at all temperatures.
The invention achieves this object by a novel
condensation product of a phenol component with an
aldehyde, which product differs basically from all
known phenol resin type.s developed for the coldbox
process or similar processes with regard to its struc-
ture, to its way of use and also to it~s method of
production.
Regarding the structure, the invention is
characterised in that the phenol component is a mixture
of an unsubstituted phenol with 15 to 40YO by weight,
based on the total phenol component, of a p-substituted
phenol.
The structural difference to the known phenol
resin types, thus, lies in the phenol component con-
tained therein. Whereas the known types either use
the unsubstituted phenol or a substituted phenol
(including also p-substituted phenols), thus using
in all cases a homogeneous phenol component it is
a prerequisite for the invention that the phenol com-
ponent is a mixture of unsubstituted phenol and a p-
substituted phenol. As a result of this p-substituted
phenol content a reinforced low viscosity linear
resin structure is obtained which can be considered
as cocausal for the improvement of the processing
~.
,,. . ~
~ 5 ~ ~ <~3
characteristics of the binder. It is particularly
surprising that this effect only occurs within the
above-indicated limit values for the p-substituted
phenol content, i.e. does not occur in linear manner
to the mixing ratio.
The substituents of the p-substituted phenol
do not have a marked influence on the sought charac-
teristics of the binder according to the invention.
However, in the case of a higher molecular weight of
the substituent the binder viscosity is somewhat
higher, so that it can then be advantageous to use p-
substituted phenol contents oriented more towards the
upper limit value. As substituents consideration is
preferably given to straight or branched alkyl groups,
but alkylene groups, aryl groups or other cyclic
groups and a1so alkyloxy groups, aryloxy groups,
halogen groups, nitro groups, acid groups, ester
groups and the like can be used, provided that they
do not impair the condensation reaction. Typical
examples which are also advantageous from the cost
standpoint are p-cresol, p-tert-butylphenol, p-
octylphenol, p-nonylphenol, p-(ethylcyclohexyl)-
phenol, p-cyclohexylphenol, etc.
The binder according to the invention can
be combined with all conventional known polyiso-
- 5a - 11~ 3
cyanates of the foundry art and requires a tertiary
amine or some other hardening catalyst which catalyzes
urethane formation. When processing, e.g. in the cold-
box process it hardens in the necessary very short time
and gives the same strength values as can be obtained
with the known phenol resin types on immediate
processing. It cannot be cured by acids or in heat.
Its very good reactivity with polyisocyanates is
scarcely temperature-dependent and is fully retained
even at low temperatures of the moulding composition
(down to below 0C.). This is an important advantage
of the invention.
Regarding the way of use, the invention is
characterised in that the condensation product is
used as a binder for a moulding composition for casting
purposes containing as further components foundry
sand, polyisocyanates and non-polar solvents and which
is cold-cured with a hardening catalyst.
The use-relative difference to the known
phenol resin types, thus, lies there in that it is
possible with the binder according to the invention
to produce moulding compositions using only non-polar
solvents, i.e. polar solvents can and must in fact
be avoided because they impair the result obtained with
the invention. Preference is given to those non-
polar aromatic solvents which are also preferred
.
- 6 -
solvents for polyisocyanates, i.e. high-boiling
aromatic hydrocarbons with a boiling range of 150
to 250C. However, it is also possible to use or add
non-aromatic, non-polar solvents such as terpene and
similar cycloaliphatic substances and optionally
also aliphatic hydrocarbons. In all cases the binder
solutions have an excellent stability at all tempera-
tures.
As a result of the use of only non-polar
solvents, which is not possible with any of the
hitherto known phenol resin types developed for poly-
urethane systems and which is a decisive advantage of
the invention, a high stability, combatible system of
all the components is obtained in the moulding com-
position mixture. Furthermore the processing time of
the finished moulding composition is increased to
values which could not hitherto be obtained. This
is a direct consequence of the fact that no polar
solvent is present which can initiate or aid cross-
linking reactions in the moulding composition.
In addition, non-polar aromatic solvents are
so hydrophobic that the finished moulding composition
only has a very low moisture sensitivity which also
contributes to the stability.
In addition, the absence of polar solvents
also reduces the tendancy of the moulding composition
to become tacky, because the interaction with the
core and moulding box surface made e.g. from wood,
plastic or metal is reduced.
me greatly increased stability of the
system containing the binder according to the invention
is also clear from its behaviour during silanisation.
It is conventional practice to add a small quantity
of silane (about 1% by weight, which increases with
the polarity of the solvent used) to cold box binders
in order-to increase the system stability and con-
sequently obtain higher strength values. In the known
phenol resin types silanisation leads to a marked
increase in strength, whilst with the binder according
to the invention it only has an insignificant action.
Therefore a system containing the binder according
to the invention is already so stable that it scarcely
requires silanisation.
Due to the low resin viscosity in con-
junction with the use of non-polar solvents moulding
compositions produced with the binder according to
the invention have an excellent flow and discharge
behaviour which has a particularly advantageous
effect with complicated moulds and cores. Here again
the binder according to the invention is superior to
known binders.
Regarding the method of production, the
invention is characterised in that the molar ratio of
phenol to aldehyde tbased on the total phenol compo-
nent~ is adjusted to the range 1:1 to 1:1.5, that the
condensation reaction starts in a water-containing
medium at temperatures up to 100C., and is sub-
sequently terminated at temperatures up to about 125C.,
accompanied by a slow separation of the water and that
the condensation catalyst is used in quantities of
0,01 to 0,1% by weight, based on the total phenol
component.
The productional difference to the known
phenol resin types, thus, lies therein, that the con-
densation reaction substantially is performed in a
water-containing medium with a less amount of aldehyde,
and that also the amount of condensation catalyst is
considerably less. For the production of the known
phenol resin types for the coldbox process, namely,
phenol and formaldehyde are reacted in a molar ratio
of more than 1:1.5 in the presence of about 1 to 2%
by weight of a metal salt of a higher carboxylic
acid (e.g. zinc naphthenate or lead neododecanoate)
as the condensation catalyst at temperatures of up
'~,,~
to about 130C., and indeed under practically water-
free conditions, in that the formed reaction water
is continuously separated. Although this may be
advantageous or necessary for the special linkage of
the phenol rings sought in the case of known coldbox
binders, it leads to a relatively high residual con-
tent of free phenol and free formaldehyde in the
binder.
As opposed to thus, the method of the
invention leads to the advantage that the phenol
component of the present binder (comprising the
unsubstututed phenol and the p-substituted phenol)
leads to a better reaction with the aldehyde (normally
formaldehyde~ during the condensation reaction, so
that both the free phenol content and the free
formaldehyde content are lower than usual in the
resin.
As a result when preparing and processing
moulding compositions the smell caused by the phenol
and the formaldehyde, together with the disadvantageous
action on the environment are reduced to a minimum
which is particularly advantageous because at the same
time there is no unpleasant smell due to the use of
polar solvents. Moreover, the method of the invention
also leads to the further advantage that for the pro-
~;~
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perties of the inventive binder, and especially
for the strength, optimally fabourable values are
obtained.
The condensation catalysts in the method
of the invention can be the known catalysts, namely
metal salts of higher carboxylic acids, particularly
fatty acids which are soluble in organic solvents
and specifically with Mn, Co, Zn, Pb, Sn and the
like as metals. However, these catalysts are used
in a much smaller quantity of only 0.01 to 0.1% by
weight and preferably 0.02 to 0.06% by weight. It
has surprisingly been found that a higher catalyst
quantity no longer leads to usable results.
~ . ~
'3~;~
Hereina~ter the invention is explained by means of
examples. Firstly the preparation of the binder and its
processing in application to the coldbox process are des-
cribed, followed by the results obtained with testpieces
according to the invention and according to the prior art.
A Preparin~ the binder
8.8 mol OI~ a phenol component (in the form of a
mizture of 91 ,0 liquified phenol and a p-substituted phenol),
13.0 mol o~ formaldehyde (as paraformaldehyde) and 0.01 to
0.1 % by ~eight, based on the phenol component of zinc octo-
ate as the condensation catalyst are placed in a glass appara-
tus with a volume of 2 litres and provided with an internal
thermometer, stirrer and condenser. The mixture was kept
at 95 C for 60 to 1&0 minutes, a clear solution being
obtained. By starting in a water-containing medium the
formaldehyde is bonded as hydrate and kept in the reaction
s~stem.
The uater was then distilled from the reaction sys-
tem and the temper~ture raised to 115 C. After standing
fo~ 60 minutes at 115 C the temperature was increased to
i25 G, accompanied by simultaneous distillation. This
was ~ollovled by a boiling period of approx. 60 to 180 minutes
at 11~ C until a viscosity of 100 poise (20 C) was obtained.
This was ~olloYIed by vacuum distillation to a product temp-
erature OL 120 C. The mixture was cooled and mixed with
the solvent as soon as no further distil]ate waS obtained.
rlhen using only aromatic hydrocarbons (boilin~
11~ ~3~33
"
range 160 to 180 C; 50 to 55 ~ resin and 50 to 45 % solvent)
stable, clear resin soluti~ns were obtained with a viscosity
of 0.2 to o.6 poise (20 C), whilst the viscosities were
higher on adding polar solvents. The yields were approx.
70 to 80 %, based on the raw material used.
The free phenol content of the resin was max.4.5 ~0,
which is much lower than that of the hitherto conventional
free phenol content of 6 to 9 %. The resin no longer had
to be designated as a "toxic product". The free formal-
dehyde content of the resin i~ also much lower than hitherto.When processing the resin measurements performed on the edge
o~ the mixer-gave a value of 1 to 2 ppm, compared witht~e
hitherto conventional values o~ 5 to 25 ppm. There~ore the
resin is not prejudicial to the environment.
B. Processin~ the binder in the coldboæ Process
100 parts by weight of foundry sand H32, 1 part by
weight of the resin solution obtairled according to A and 1
part by weight of a polyisocyanate solution (comprising 85 %
industrial polyisocyanate based on diphenyl-methane-diisocyan-
ate and 15 % aromatic hydrocarbons with a boilin range o~ ~60to 180 C), optionally accompanied by the addition of a silane
were mixed together to give a moulding composition, whereby
firstly the resin solution and then the polyisocyanate sol-
ution was added to the sand.
Thi~ mol~ding composition Yas moulde~ to moulding
articles either immediately or a~ter a predetermined proces-
sing time (i.e. after storing in the mixed, but still not
1.~ 35~;~
-13-
cured state), followed by curing by "gasing" with a tertiary
amine. The strength characteristics of the cured moulded
articles were then determined.
C. Characteristics of the moulded articles obtained
The characteristics of the cured moulded articles,
together with the necessary individual data are given in the
attached tables.
Table 1 illustrates by means of a binder covered
by the range of the invention, the good strength values which
can be obtained and in particular that the good strength values
are maintained even with long processing periods. After a
180 minute processing time e.g. the ~inal strengths (7 day
values) have only dropped by 23 %. However, in the case
of the known phenol resin types after this or even shorter
processing times the strength values have generally reached
the low values ~hich only occur after about 300 minutes with
the binder used as a basis in Table 1.
Table 2 uses the same binder as Table 1 and illu-
strates the influence of the processing temperatures. The
table shovJs that the characteristics of the moulded article
formed are substantially independent of the processin~ temp-
eratures not only in the case of immediate processing, but
also after a processing time of 60 minutes.
Using the same binder Table 3 shows the influence
of different solvents (including polar solvents not in accord-
ance with the invention), ~r~hilst Table 4 shows the influence
of adding silane. These Tables show that the strengths
1 ~ 3
(particularly the 7 day values) are lower both in the case of
immediate processing and with a processing time of 60 minutes
if the solvent contains a proportion of a polar component and
that a silane addition has a much smaller action in the case
of the non-polar solvents according to the invention than
with solvents containing a polar component.
Finally Table 5 shows the limit values for the p-
substituted phenol content of the binder and ror the con-
densation catalyst quantity used. In the case of 10 %
p-substituted phenol contents (not according to the invention)
although good strengths and still usable processing times are
obtained the resin solutions are no longer stable at temper-
atures below 20 C. Conversely with contents of 49 % of
p-substituted phenol (also not according to the invention)
the strength values and procesaing times drop. Catalyst
quantities in excess of 0.10 ~0 (no longer according to the
invention) lea to undesirably high viscosity values and
unsatisfactory strength characteristics.
TABLE 1
Binder prepared as under A with as the phenol com-
ponent 23 ~ by weight of p-tert-butylphenol and the residue
unsubstituted phenol, with 0.02 ~0 by weight zinc octoate as
the condensation catalyst and 55 % resin and 45 % aromatic
hydrocarbons of boiling range 160 to 180 C as the resin
solution.
Processing ie as defined under B with a temperature
of 25 C and no silane addition, The bending strengths
are gi~en in ~/cm'.
Testin,~ the cured moulded articles
Processing of Imr,~ed-
mouldin~ com~osition iately 4~ min 24 h 48 h 7 d
Immediately 235 490 519 530 510
A~ter 60 min 226 471 550 519 510
Af'ter 120 min 206 422 481 451 451
Af'ter 180 min 167 343 402 392 392
A~ter 240 min 127 245 304 304 304
After 300 min 88 206 235 216 235
Table 2
3inder as in Table 1 but the resin solution com-
prises 50 % resin ~nd 50 ~0 aromatic hydrocarbons o~ boiling
range 160 to 180 CO
The processing is as in Table 1, but with the
~ollowing temperatuIIes :
Range I : Sand 20 to 22 C
Mixture 23 to 25 C
Chamber 19 to 22 C
Range II : Sand 2 to 3 C
Mixture 8 to 10 C
Ghamber 1 to 5 C
3ending stren~ths in ~/cm2.
Testin~ the cured moulded articles
Processing of Immed-
mouldin~ com~osition iately 45 min 24 h 7 d
Immediately rOr
range I 205 54 648 677
After 60 min for
range I 206 49 598 628
Immediately for
range II 196 451 549 549
After 60 min for
range II 196 343 441 441
Table ~
3inder as given in Table 1 but the resin solution
consists of 50 % resin and 50 % s~lvent..
The solvent comprises aromatic hydrocarbons with
boiling range 160 to 180 C, either pure or with the rurther
solvent contents given in the Table,
Processing is as in Table 1. The bending strengths
are given in ~/cm2.
~ ~.`,0~!33
--17--
Solvent lli~ture immediately ~rixture stored for
processed 60 min
Testin~ the cured mouided articles
Aromatics 45 244S 45 24 48
with imm. min minmin 7d imm.. min min min 7d
No addition 215 490 549 - 538 216 412 540 - 598
20 ~ acetal-
dehyde-
diethyl-
acetate 226 441 490 - 549 226 412 490 - 500
20 0:70 dibutyl
sebacate 235 480 490480 441 235 480 510 480 412
20 ~0 n-
hexyl-
acetate 216 462 412382 363 216 432 373 382 333
20 ~ iso-
phorone 166 392 333323 323 177 382 402 382 304
10 % ethyl
acetate 196 462 471 - 559 206 402 470 - 530
20 % DL-
limonene
(terpene) 206 471 677 - 755 235 500 687 - 775
40 ~0 D~-
limonene
(terpene) 1 96 51 0 627 - 755 245 530 647 - 755
50 'Jt DL-
limonene
(terpene) 21 6 500 678 - 755 265 530 657 - 765
Table 4
Binder as given in Table 3, but the resin solution
comprises 55 % resin and 45 ~0 solvent.
Processin~ is as in Table 1, but either with 0.3 ~O
by ;~eight silane addition (S) or without silane addition (0).
The bending strengths are given in N/cm2.
1~ 3-~3
l ~
Solvent Mixture immediately Mixture stored for
processed 60 min
Testin~ the cured moulded articles
Aromatics 45 24 48 45 24 48
with imm. min min min 7d imm. min min min 7d
No addition S 285 539 638 647 667 275 480 569588 657
11 ~ n-
hexylacetate S 245 500 451441 441 225 441 422422 402
22 % n-
hexylacetate S 216 461 412382 363 216 432 373382 353
33 % iso-
phorone S 206 480 343343 333 186 441 363333 304
33 % DL-
limonen
(terpene) S 285 520 647696 735 343 549 628677 735
66 % DL-
limonen
(terpene) S 294 579 638667 708 265 500 637657 706
lO No addition 0 285 490 53 ~ 569 255 461 53 ~ 529
33 % dibutyl
sebacate 0 275 432 382 - 275 255 422 422 - 304
; 33 % iso-
phorone 0 196 432 225186 147 176 363 245176 137
Table 5
Binder as in Table 1, but the phenol component has a
different p-substituted phenol content as given belo~ and the
condensation catalyst has a di~ferent zinc octoate quantity
given belo1.q.
Processing is as in Table 1 and the bending strengths
are giv~n in N/cm2.
`` 11703~33
--1 9--
~estpiece Catalys~ p-sub- Viscosity Testing of cured
_no. % stituted (~oise) moulded articles
phenol jO Immed-
iately 24~ 48h
0.01 1 0 0.2798 491 520
2 0.02 10 0051 186 579 589
3 o.o6 10 0.80 226 628 608
4 0.12 1 0 2.2Q255 530 540
0.01 23 0.20t68 598 598
0002 23 0.31206 579 589
7 0.06 23 0.62255 559 569
8 0.12 23 1.52 235 51 0 471
9 0.01 36 00 23 177 540 559
0.02 36 0.30206 530 549
11 oOo6 36 0.3921 6 51 0 51 0
1 2 001 2 36 o.69216 491 471
13 0001 49 0.20167 451 432
14 0.02 49 0024167 451 422
oOo6 49 0.291 86 41 2 392
16 0.12 49 Oo56167 392 373
