Note: Descriptions are shown in the official language in which they were submitted.
CA 02349878 2006-08-17
Binder System for Producing Polyurethane-Based Cores and Melting
Moulds
This invention deals with a polyurethane based binder system for the
manufacture of foundry cores and molds.
The method which has come into existence for the manufacture of cores, known
as the "Cold-Box-Process" or the "Ashland-Process", has achieved a top
position
in the foundry industry. With this method, two-component polyurethane systems
are used for the bonding of sand. The first component consists of a solution
of
some polyois which contain at least two OH groups per molecule. The second
component is a solution of some isocyanates with at least two NCO groups per
molecule. The curing of the binder system follows with the help of basic
catalysts. Liquid bases can be added to the binder system before the molding
stage, in order to bring the two components to reaction (US-A-3,676,392).
Another possibility, according to US-A-3,409,579, is to pass gaseous tertiary
amines through the molding material-/binder system-mixture after the shaping.
In both the above-named patents, phenolic resins are used as polyols, which
are
prepared through condensation of phenol with aidehydes, preferably
formaldehyde, in the liquid phase, at temperatures of up to around 130 C in
the
presence of divalent metal catalysts. The manufacture of such phenolic resins
is
described in detail in US-A-3,485,797. In addition to unsubstituted phenol,
substituted phenols, especially o-cresol and p-nonyl phenol, can be used (for
example, EP-A-183 782). As additional reaction components, according to EP-
B-0 177 871, aliphatic monoalcohols with one to eight carbon atoms can be used
in the manufacture of phenolic resins. Through alkoxylation, the binder
systems
should have a higher thermal stability. As solvents for the phenolic
components,
mixtures of high-boiling point polar solvents (for example, esters and
ketones)
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and high boiling point aromatic hydrocarbons should mainly be used. The
polyisocyanates, on the other hand, are preferably dissolved in high boiling
point
aromatic hydrocarbons. In European Patent application EP-A-0 177 599,
formulations are described, which can do w+thout aromatic solvents entirely,
or,
to a great extent, as a result of the use of fatty acid methyiesters. The
fatty acid
methylesters are used either as stand-alone solvents or with the addition of
polarity-raising solvents (phenolic-components), or, as the case may be,
aromatic
solvents (isocyanate components). Cores manufactured with this binder system
are particularly easy to remove from the mold tooling.
In practice, however, binder systems formulated according to EP-A-O 771 599,
display a serious disadvantage: So much smoke develops during the casting
process, that in many foundries, they would not make it past the experimental
stage.
In order to comply with the increasingly higher environmental standards and
health and safety requirements, there has for many years been a growing
interest in binder systems which contain no, or very few, aromatic hydrocarbon
solvents.
For these reasons, the task of the present invention was to develop a low odor
or
odor-free binder system. In addition, the invention has the task of making
available a binder system which exhibits a low incidence of smoke buildup. To
these ends, the cores/molds manufactured with this binder system should
exhibit
a good flexural strength, and above all, a good immediate strength.
This task was solved through a binder system encompassing a phenolic resin
component and a polyisocyanate component characterized by the phenolic resin
component having an alkoxy-modified phenolic resin, whereby less than 25
mole-% of the phenolic hydroxy groups are etherified by a primary or secondary
aliphatic alcohol with I to 10 hydrocarbons.
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Furthermore the invention involves molding compounds which include
aggregates and a binder system based on the invention, of up to 15% by weight
compared to the weight of the aggregates.
Likewise, the invention involves processes for the manufacture of cores/molds
which include
a. Mixing of aggregates with the invention based binder system in a definite
quantity of up to 15 % by weight, compared to the quantity of aggregate;
b. Introduce the compound in Step (a) into a mold;
c. Cure the casting compound in the mold, in order to obtain a self-supporting
form; and
d. Afterwards remove the molded casting compound in Step ( c) from the form
and, after further curing, one obtains a hard, solid, cured molded foundry
piece.
The molded pieces thus obtained can, according to the invention, be used in
metal foundries.
Selecting an alkoxy-modified phenolic resin that exhibits low viscosity and
favorable polarity is fundamental to the invention. According to the
invention, the
alkoxy-modified phenolic resin makes it possible to reduce the quantities of
solvents needed, both in the phenolic resin component and also in the
isocyanate component. Furthermore, the use of aromatic hydrocarbons in one or
both of the binder components can be dispensed with. Through the combination
of the alkoxy-modified phenolic resin with oxygen-rich, polar, organic
solvents,
improved immediate strengths are achieved with reduced build up of smoke.
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The addition of fatty acid ester has a positive effect on the separation
effect and
on moisture resistance.
Phenolic resins are manufactured by condensation of phenols and aldehydes
(Ullmann's Encyclopedia of Industrial Chemistry, Bd. A19, page 371 ff, 5th,
edition, VCH Publishing House, Weinheim). In the framework of this invention,
substituted phenols and mixtures thereof can also be used. All conventionally
used substituted phenols are suitable. The phenolic binders are not
substituted,
either in both ortho-positions or in one ortho- and in the para-position, in
order to
enable the polymerization. The remaining ring sites can be substituted. There
is
no particular limitation on the choice of substituent, as long as the
substituent
does not negatively influence the polymerization of the phenol and the
aldehyde.
Examples of substituted phenois are alkyl-substituted phenols, aryl-
substituted
phenols, cycloalkyl-substituted phenols, alkenyl-substituted phenols, alkoxy-
substituted phenols, aryloxy-substituted phenols and halogen-substituted
phenols.
The above named substituents have 1 to 26, and preferably I to 12, carbon
atoms. Examples of suitable phenols, in addition to the especially preferred
un-
substituted phenols, are o-cresol, m-cresol, p-cresol, 3,5-xylol, 3,4-xylol,
3,4,5-
trimethyl phenol, 3-ethylphenol, 3,5-diethylphenol, p-butylphenol,
3,5-dibutylphenol, p-amylphenol, cyclohexylphenol, p-octylphenol, 3,5-
d icyclohexyl phenol, p-crotylphenol, p-phenylphenol, 3,5-dimethoxyphenol,
3,4,5-
trimethoxyphenol, p-ethoxyphenol, p-butoxyphenol, 3-methyl-4-methoxyphenol,
and p-phenoxyphenol. Especially preferred is phenol itself. The phenols can
likewise be described with the general formula:
OH
B B B 4 -
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where A, B and C can be hydrogen, alkyl radicals, alkoxy radicals or halogens.
All aldehydes which are traditionally used for the manufacture of phenolic
resins,
can be used within the scope of the invention. Examples of this are
formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, and
benza{dehyde. Preferably, the aldehydes commonly used should have the
general formula R'CHO, where R' is hydrogen or a hydrocarbon radical with 1-8
carbon atoms. Particularly preferred is formaldehyde, either in its diluted
acqueous form or as paraformaidehyde.
In order to obtain the phenolic resins on which this invention is based, a
molar
number of the aldehyde should be used which is at least equivalent to the
molar
number of the phenolic component. A molar ratio of aldehyde to phenol is
preferred of at least 1:1.0, with at least 1:0.58 being the most preferable.
In order to obtain alkoxy-modified phenolic resins, primary and secondary
aliphatic alcohols should be used with an OH-group containing from 1 to 10
carbon atoms. Suitable primary or secondary alcohols include, for example,
methanol, ethanol, n-propanol, isopropanol, n-butanol, and hexanol. Alcohols
with 1 to 8 carbon atoms are preferred, in particular, methanol and butanol.
The manufacture of alkoxy-modified phenolic resins is described in EP-B-0 177
871. They can be manufactured using either a one-step or a two-step process.
With the one-step-process, the phenolic components, the aidehyde and the
alcohol are brought to a reaction in the presence of suitable catalysts . With
the
two-step-process an unmodified resin is first manufactured, which is
subsequently treated with alcohol.
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The ratio of alcohol to phenol influences the properties of the resin as well
as the
speed of the reaction. The molar ratio of alcohol to phenol amounts to less
than
0.25, so that less than 25 mole-% of the phenolic hydroxy groups are ethered,
A
molar ratio of from 0.18 - 0.25 is preferred. If the molar ratio of alcohol to
phenol
amounts to more than 0.25, the moisture resistance decreases.
Suitable catalysts are divalent salts of Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca
and
Ba. Zinc acetate is preferred.
Alkoxylation leads to resins with a low viscosity. The resins predominantly
exhibit ortho-ortho benzyl ether bridges and furthermore, in ortho- and para-
position to the phenolic OH-groups, they exhibit alkoxymethylene groups with
the
general formula -(CHZO)õR. In this case R is the alkyl group of the alcohol,
and n
is a small whole number in the range of 1 to 5.
All solvents, which are conventionally used in binder systems in the field of
foundry technology, can be used in the systems which are the subject of the
invention. It is even possible to use aromatic hydrocarbons in large
quantities as
essential elements in the solution, except that those solvents mentioned at
the
beginning, which might endanger health, safety, and the environment, should be
avoided. For that reason, the use of oxygen-rich, polar, organic solvents are
preferred as solvents for the phenolic resin components. The most suitable are
dicarboxylic acid ester, glycol etherester, glycol diester, glycol diether,
cyclic
ketone, cyclic ester (lactone) or cyclic carbonate. Cyclic ketone and cyclic
carbonate are preferrred. Dicarboxylic acid ester exhibits the formula RIOOC-
R2-COOR1, where Ri, represents an independent alkyl group with 1-12, and
preferably 1-6 carbon atoms, and R2 is an alkylene group with 14 carbon atoms_
Exampies are dimethylester from carboxylic acids with 4 to 6 carbon atoms,
which can, for example, be obtained under the name dibasic ester from DuPont.
Glycol etheresters are binders with the formula R3-O-R4-OOCR5, where R3
represents an alkyl group with 1-4 carbon atoms, R4 is an alkylene group with
2-4
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carbon atoms, and R5 is an alkyl group with 1-3 carbon atoms (for exampie
butyl
glycolacetate), with glycol etheracetate being preferred. Glycol diesters
exhibit
the general formula R5COO-R4-OOCR5 where R4 and R5 are as defined above
and the remaining R5, are selected, independent of each other (for example,
propyleneglycol diacetate), with glycol diacetate being preferred. Glycoi
diether
is characterized by the formula %-O-R4-O-R3, where R3 and R4 are as defined
above and the remaining Pq are selected independent of each other (for
example,
dipropyleneglycol dimethylether). Cyclic ketone, cyclic ester and cyclic
carbonate with 4-5 carbon atoms are likewise suitable (for example, propylene
carbonate). The alkyl- and alkylene groups can be branched or unbranched.
These organic polar solvents can preferably be used either as stand-alone
solvents for the phenolic resin or in combination with fatty acid esters,
where the
content of oxygen-rich solvents in a solvent mixture should predominate. The
content of oxygen-rich solvents should come to more than 50% by weight,
preferably more than 55% by weight.
Reducing the content of solvents in binder systems can have a positive effect
on
the development of smoke. Whereas conventional phenolic resins generally
contain around 45% by weight and, sometimes, up to 55% by weight of solvents,
in order to achieve an acceptable process viscosity (of up to 400 mPa-s), the
amount of solvent in the phenolic-component can be restricted to at most 40%
by
weight, and preferably even 35% by weight, through the use of a low viscosity
phenolic resin called for in this invention. The dynamic viscosity is
determined
according to the Brookfield Head Spindle Process.
If conventional non alkoxy-modified phenolic resins are used, the viscosity
with
reduced quantities of solvent lies well outside the range which is favorable
for
technical applications of up to around 400 mPa-s. ln some parts, the
solubility is
also so bad that at room temperature phase separation can be observed. At the
same time the immediate strength of the cores manufactured with this binder
system is very low_ Suitable binder systems exhibit an immediate strength of
at
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(O009
least 150 N/cmz when 0.8 parts by weight each of the phenolic resin and
isocyanate component are used for 100 parts by weight of an aggregate, like,
for
example, Quarzsand H32 (s. EP-A-0 771 599 or DE-A-4 327 292).
The addition of fatty acid ester to the solvent of the phenolic component
ieads to
especially good release properties. Fatty acids are suitable, such as, for
example, those with 8 to 22 carbons, which are esterified with an aliphatic
alcohol. Usually fatty acids with a natural origin are used, like, for
example,
those from tall oil, rapeseed oil, sunflower oil, germ oil, and coconut oil.
Instead
of the natural oils, which are found in most mixtures of various fatty acids,
single
fatty acids, like palmitic fatty acid or myristic fatty acid can, of course,
be used.
Aliphatic mono alcohols with 1 to 12 carbons are suitable for the
esterification of
fatty acids. Alcohois with 1 to 10 carbon atoms are preferred, with alcohols
with
4 to 10 carton atoms being especially preferred. Based on the low polarity of
fatty acid esters, whose alcohol components exhibit 4 to 10 carbon atoms, it
is
possible to reduce the quantity of fatty acid esters, and to reduce the
buildup of
smoke. A line of fatty acid esters is commercially obtainable.
Surprisingly, it has been shown that fatty acid esters, whose alcohol
components
contain from 4 to 10 carbon atoms, are especially advantageous., since they
also
give binder systems excellent release properties, when their content in the
solvent of the phenolic component amounts to less than 50% by weight. As
examples of fatty acid esters with longer alcohol components, are the butyl
esters of oleic acids and tall oil fatty acid, as well as the mixed octyl-
decylester of
tall oil fatty acids.
Through the use of the invention-based alkoxy-modified phenolic resins,
aromatic
hydrocarbons can be avoided as solvents for the phenolic component. This is
because of the excellent polarity of the binders. Oxygen-rich organic, polar
solvents, can now be used as stand-alone solvents. Through the use of the
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invention-based alkoxy-modified phenolic resins, the quantity of solvents
required
can be restricted to less than 35% by weight of the phenolic component. This
is
made possible by the low viscosity of the resins. The use of aromatic
hydrocarbons can, moreover, be avoided. The use of invention based binder
systems with at least 50% by weight of the above named oxygen-rich, polar,
organic solvents as components in the solvents of the phenolic components
leads, moreover, to a doubtlessly lower development of smoke, in comparison
with conventional systems with a high proportion of fatty acid esters in the
solvent.
The two components of the binder system include an aliphatic, cycloaliphatic
or
aromatic polyisocyanate, preferably with 2 to 5 isocyanate groups. Based on
the
desired properties, each can also include mixtures of organic isocyanates.
Suitable polyisocyanates include aliphatic polyisocyanates, like, for example,
hexamethylenediisocyanate, alicyclic polyisocyanates like, for example, 4,4'-
dicyclohexylmethanediisocyanate, and dimethyl derivates thereof. Examples of
suitable aromatic polyisocyanates are toluol-2,4-diisocyanate, toluol-2,6-
diisocyanate, 1,5-napththalenediisocyanate, triphenylmethanetriisocyanate,
xylylenediisocyanate and its methyl derivatives, polymethylenepolyphenyl
isocyanate and chlorophenylene-2,4-diisocyanate. Preferred polyisocyanates
are aromatic polyisocyanates, in particular, polymethylenepolyphenyl
polyisocyanates such as diphenylmethane diisocyanate.
In general 10 -- 500 % by weight of the polyisocyanates compared to the weight
of the phenolic resins are used. 20 - 300 % by weight of the polyisocyanates
is
preferred. Liquid polyisocyanates can be used in undiluted form, whereas solid
or viscous polyisocyanates can be dissolved in organic solvents. The solvent
can consist of up to 80% by weight of the isocyanate components. As solvents
for the polyisocyanate, either the above-named fatty acid esters or a mixture
of
fatty acid esters and up to 50% by weight of aromatic solvents can be used.
Suitable aromatic solvents are naphthalene, alkyl-substituted naphthalenes,
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alkyl-substituted benzenes, and mixtures thereof. Especially preferred are
aromatic solvents, which consist of mixtures of the above named aromatic
solvents and which have a boiling point range of between 1400 C and 230 C.
However, preferably no aromatic solvents are used. Preferably, the amount of
polyisocyanate used results in the number of the isocyanate group being from
80
to 120% with respect to the number of the free hydroxyl group of the resin.
In addition to the already mentioned components, the binder systems can
include
conventional additives, like, for example, silane (US 4,540,724), drying oils
(US
4,268,425) or "Komplexbildner" (WO 95/03903). The binder systems are offered,
preferably, as two-component-systems, whereby the solution of the phenolic
resin represents one component and the polyisocyanate, also in solution, if
appropriate, is the other component. Both components are combined and
subsequently mixed with sand or a similar aggregate, in order to produce the
molding compound. The molding compound contains an effective binding
quantity of up to 15% by weight of the invention-based binder system with
respect to the weight of the aggregate. It is also possible to subsequently
mix
the components with quantities of sand or aggregates and then to join these
two
mixtures. Processes for obtaining a uniform mixture of components and
aggregates are known to the expert. In addition, if appropriate, the mixture
can
contain other conventional ingredients, like iron oxide, ground flax fiber,
xylem,
pitch and refractory meal (powder).
In order to manufacture foundry molded pieces from sand, the aggregate should
exhibit a sufficiently large particle size. In this way the founded piece has
sufficient porosity, and fugitive gasses can escape during the casting
process. In
general at least 80% by weight and preferably 90% by weight of the aggregate
should have an average particle size of less than or equal to 290 pm. The
average particle size of the aggregate should have between 100 and 300 pm.
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For standard founded pieces, sand is preferred as the aggregate material to be
used, where at least 70% by weight, and preferably more than 80% by weight of
the sand is silicon dioxide. Zircon, olivine, aluminosilicate sands and
chromite
sands are likewise suitable as aggregate materials.
The aggregate material is the main component in founded pieces. In founded
pieces from sand for standard applications, the proportion of binder in
general
amounts to up to 10% by weight, and often between 0.5 and 7% by weight, with
respect to the weight of the aggregate. Especially preferred is 0.6 to 5% by
weight of binder compared to the weight of the aggregate.
Although the aggregate is primarily added dry, up to 0.1 % by weight of
moisture
can be tolerated, with respect to the weight of the aggregate. The founded
piece
is cured so that it retains its exterior shape after being removed from the
mold.
Conventional liquid or gaseous curing systems can be used for hardening in the
invention-based binder system. A slightly volatile tertiary amine, like, for
example, triethylamine or dimethylethylamine, as described in US-A-3,409,579,
can also be passed through the founded piece,
It is further possible, to add a liquid amine to the molding compound in order
to
cure it. After removing the piece from the mold, further hardening takes place
in
the well-known way, finally resulting in the finished piece.
In a preferred implementation, silane with the general formula (R'O~Si is
added
to the molding compound before the curing begins. Here, R' is a hydrocarbon
radical, preferably an alkyl radical with 1- 6 carbon atoms, and R is an alkyl
radical, an alkoxy-substituted alkyl radical or an alkyl amine-substituted
amine
radical with alkyl groups, which have 1-6 carbon atoms. The addition of from
0.1
to 2% by weight with respect to the weight of the binder system and catalysts,
reduces the moisture sensitivity of the system. Examples of commercially
obtainable silanes are Dow Corning Z6040 and Union Carbide A-187 (y-
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glycidoxypropyltrimethoxysilane), Union Carbide A 1100 (r aminopropyl
triethoxysilane), Union Carbide A-1120 (N-(3-(aminoethyl)-y-amino-
propyltrimethoxysilane) and Union Carbide A1160 (ureidosilane).
If applicable, other additives can be used, including wetting agents and sand
mixture extending additives (English Benchlife-additives), such as those in US
4,683,252 or US 4,540,724. In addition, mold release agents like fatty acids,
fatty alcohols and their derivatives can be used, but as a rule, they are not
necessary.
The invention is further clarified by the following examples.
Examples
If not otherwise specified, all percentages are by weight.
1. Manufacture of phenolic resins
The raw materials in Table I are placed in a reaction vessel fltted with
reflux
condenser, thermometer and agitator. The temperature is raised uniformly,
under agitation, to 105 -115 C, and held there until a refractive index of
1.5590 is reached. Next the condenser is switched over to distillation and the
temperature is brought up to 124 -126 C over the course of an hour. At this
temperature, further distillation should occur until obtaining a refractive
index
of 1.5940. Next a vacuum is applied, and distillation is continued under
reduced pressure, until reaching a refractive index of 1.600. The yields
amount to around 83% in Example 1 and around 78% in Example 2.
Table I
Exam le 1 2
not according to the according to the invention
invention
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henol 2130.7 1770.6
paraformaidehyde 91 % 865.3 g 984.3 g
n-butanol - 279.6
zinc acetate-dih drate 1.0 g 1.5
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2. Manufacture of phenolic resin solutions
With the phenolic resin manufactured according to the above instructions, the
solutions shown in Table 11 are manufactured. Trade names are shown with an
(H).
Table It
Example 1A 1B 1C 1D
Not accordin to the invention
Phenolic resin 1 67.5% 67.5% 67.5% 67.5%
DBE (H) 19.0% 24.5% 27.0% 32%
Forbiol 102 (H) 13.0% 7.5% 5.0%
Silane 0.5% 0.5% 0.5% 0.5%
viscosity 2 phases 659 617 561
mpa-s
Table IlI (Continuation)
Example 220. 26 2C 2D 2E 2F 120 2H
acoDrdin to the lnvention
henolit resin 67.5% 67.5% 67.5% 67.5% 6.5% 67_5% 67.5% 67.5%
DBE ' 19.0% 24.5 /v 27.0% 3.0%
9u 1 col acetate 32.0%
ethylene Blyaol- 32.0%
diacetate
diprcpyiene glycoi- 32.0%
dimeth ether
ro lenecarbonats 32.0%
Forbiol 102 13.0 4 7.5% 5.0%
silane 0.5% 0.5% O. 0.5% 0.5% 0.5% 0.5% 0.5%
viscosl mPa-s 289 280 6d 241 217 297 211 338
a) DBE, dibasic ester, dimethyiester mixture of dicarbonic acids with 4 to 6
carbon atoms (Dupont)
b) Forbiol 102, butyl ester of tall oil fatty acids (Arizona Chemical)
The phenolic resin solution, 1A, separates into two phases after cooling down
to
room temperature, and, for that reason, will not be examined further. The
viscosity of the phenolic resin solutions 1 B-1 D lies way outside the
favorable
range for technical applications (i.e., up to around 400 mPa.s)
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3. Manufacture of polyisocyanate solutions
As component II of the polyurethane-binder system, the solutions shown in
Table III are manufactured.
Table lll
Exam te 3A 3B 3c
According to the invention
diphenyl methane di- 80% 60 /v 80%
iso Aate techn. MDI)
Forbio1102 (H) 19.8% 10%
Forbiol 152 H ` 19.8%
Solvesso 100 (H)" 9.8%
Acid chloride 0.2% 0.2% 0.2%
Forbiol 152, mixture of octyl-decylester of tall oil fatty acids (Arizona
Chemical)
d) Solvesso 100, mixture of aromatic hydrocarbons (Exxon)
4.) Manufacture and testing of the molding material-/binder system-mixture
The following information applies to the manufacture of the molding material-
/binder system-mixture:
0.5 parts by weight of the phenolic resin solution from Table II, and 0.8
parts
by weight of the polyisocyanate solution from Table III are added to 100 parts
by weight of Quarzsand H 32 (Quarzwerke GmbH, Frechen), in the order
given, and mixed intensively in a laboratory mixer. With this mixture, test
bodies are manufactured according to DIN 52401, which are cured by
gassing with triethylamine (10 seconds at 4 bar pressure, followed by 10
seconds purging with air).
The flexural strength of the test bodies can be determined by GF-methods. In
this way the flexural strength of the test bodies is tested immediately after
they are manufactured (immediate strength) as well as after 1, 2, and 24
hours.
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The results are shown in Table IV
Table IV
Attempt 1 2 3 4 5 6 7 8 9 10 11 12 13
component 1 1 B 1 C 1 D 2A 2B 2C 2D 2E 2F 2G 2H 2D 2D
Component2 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3B 3C
not acco ing to the according to the inventlon
inventfon
Strength (IWcm2)
Immediate 105 120 140 205 235 225 205 225 200 230 180 1190 210
1h 380 355 390 555 575 565 580 560 555 530 430 580 500
2h 400 405 400 555 575 565 580 560 570 590 440 585 530
24h 555 540 530 590 630 610 590 570 570 600 550 590 570
From Table 110 one can recognize
- Binder systems which are formulated with conventional phenolic resins
(Attempt 1-3) have fundamentally lower initial strengths than those binder
systems which are based on the invention (Attempts 4-13). Also the increase
in strength over time is undoubtedly slower.
- The strengths, above all, the immediate strength, of all invention-based
binder
systems (Attempt 4-13), are the same within the precision of the test method.
There is no identifiable dependency on the content of fatty acid ester/polar
solvents.
- Both the fatty acid butyl ester and the fatty acid octyl-/decyl ester are
equally
suitable for the invention-based binder systems (Attempts 7 and 12).
- Combination with aromatic solvents is just as possible (Attempts 7 and 13)
' Translator's Note - Should be Table IV
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5. Observation of smoke development
GF-test bars are kept in the oven 1 minute at 650 C. After removing them,
the development of smoke is observed against a dark background and
assessed with a rating of 10 (very strong) -1 (scarcely perceptible).
The results are shown in Table V.
Table V
Cores from Attempt In 4 5 6 7 8 9 10 11 12
Table IV
Component I 2A 2B 2C 2D 2E 2F 2G 2H 2D
component 2 3A 3A 3A 3A 3A 3A 3A 3A 3B
vaiue 10 $ 8 5 5 5 5 5 5
From Table V it follows that the development of smoke eases up when one
reduces the fatty acids in favor of oxygen-rich solvents.
Casting research with cores which correspond to the composition of Attempts 4
and 7, confirmed the above results.
17
