U.S. patent application number 10/661731 was filed with the patent office on 2004-07-08 for polyurethane based binder system for the manufacture of foundry cores and molds.
This patent application is currently assigned to Ashland Inc.. Invention is credited to Koch, Diether, Roze, Jean-Claude, Weicker, Gunther, Werner, Andreas.
Application Number | 20040132861 10/661731 |
Document ID | / |
Family ID | 30001649 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040132861 |
Kind Code |
A1 |
Roze, Jean-Claude ; et
al. |
July 8, 2004 |
Polyurethane based binder system for the manufacture of foundry
cores and molds
Abstract
A cold-box process for preparing a foundry shape, e.g. mold or
core, that uses a binder comprising a phenolic resin component and
an isocyanate component, wherein the phenolic resin component
comprises (a) an alkoxy-modified phenolic resole resin and (b) an
oxygen-rich polar, organic solvent component, which contains a
fatty acid ester.
Inventors: |
Roze, Jean-Claude; (Gaillon,
FR) ; Weicker, Gunther; (Solingen, DE) ; Koch,
Diether; (Mettmann, DE) ; Werner, Andreas;
(Erding, DE) |
Correspondence
Address: |
David L. Hedden
ASHLAND INC.
P.O. Box 2219
Columbus
OH
43216
US
|
Assignee: |
Ashland Inc.
|
Family ID: |
30001649 |
Appl. No.: |
10/661731 |
Filed: |
September 12, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10661731 |
Sep 12, 2003 |
|
|
|
09806864 |
Jul 9, 2001 |
|
|
|
09806864 |
Jul 9, 2001 |
|
|
|
PCT/EP99/08419 |
Nov 4, 1999 |
|
|
|
Current U.S.
Class: |
523/139 ;
164/526 |
Current CPC
Class: |
B22C 1/2273
20130101 |
Class at
Publication: |
523/139 ;
164/526 |
International
Class: |
B22C 001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 1998 |
DE |
198 50 833 A 1 |
Claims
We claim:
1. A process for preparing a foundry shape by the cold-box process
which comprises: (a) forming a foundry mix comprising a major
amount of aggregate and an effectively binding amount of a binder
system comprising: (1) a phenolic resole resin component, and (2)
an isocyanate component, wherein the phenolic resin component
comprises (a) an alkoxy-modified phenolic resole resin component
such that the mole ratio of alcohol to phenol used to prepare said
alkoxy-modified phenolic resole resin is less than 0.25:1.0, and
(b) at least one oxygen-rich, polar organic solvent component,
wherein the solvent portion of the phenolic resin component of the
binder system amounts to no more than 40% by weight, based upon the
weight of the phenolic resin component, and the amount of
oxygen-rich polar organic solvent is at least 50 weight percent
based on the total weight of the solvent in the phenolic resin
component; and wherein either the phenolic resin component,
isocyanate component, or both of said components contain a fatty
acid ester having from 1 to 12 carbon atoms in the alcohol chain of
the fatty acid ester; (b) forming a foundry shape by introducing
the foundry mix obtained from step (a) into a pattern; (c)
contacting foundry shape mix with a volatile tertiary amine
catalyst; and (d) removing the foundry shape of step (c) from the
pattern.
2. The process of claim 1 wherein the oxygen-rich polar, organic
solvent is selected from the group consisting of glycol ether
esters, glycol diesters, glycol diethers, cyclic ketones, cyclic
esters, cyclic carbonate, and mixtures thereof.
3. The process of claim 2 wherein the fatty acid ester is part of
the phenolic resin component and is derived from an alcohol having
from 4 to 10 carbon atoms.
4. The process of claim 3 wherein the fatty acid ester is the butyl
ester of tall oil fatty acids.
5. The process of claim 4 wherein the amount of said binder in said
foundry mix is about 0.6 percent to about 5.0 percent based upon
the weight of the aggregate.
6. A process of casting a metal which comprises: (a) preparing a
foundry shape in accordance with claims 1, 2, 3, 4, or 5; (b)
pouring said metal while in the liquid state into and a round said
shape; (c) allowing said metal to cool and solidify; and (d) then
separating the molded article.
7. A binder system comprising: (a) a phenolic resole resin
component, and (b) an isocyanate component, wherein the phenolic
resin component comprises (a) an alkoxy-modified phenolic resole
resin component such that the mole ratio of alcohol to phenol used
to prepare said alkoxy-modified phenolic resole resin is less than
0.25:1.0, and (b) at least one oxygen-rich, polar organic solvent
component, wherein the solvent portion of the phenolic resin
component of the binder system amounts to no more than 40% by
weight, based upon the weight of the phenolic resin component, and
the amount of oxygen-rich polar organic solvent is at least 50
weight percent based on the total weight of the solvent in the
phenolic resin component; and wherein either the phenolic resin
component, isocyanate component, or both of said components contain
a fatty acid ester having from 1 to 12 carbon atoms in the alcohol
chain of the fatty acid ester.
8. The binder system of claim 7 wherein the oxygen-rich polar,
organic solvent is selected from the group consisting of glycol
ether esters, glycol diesters, glycol diethers, cyclic ketones,
cyclic esters, cyclic carbonate, and mixtures thereof.
9. The binder system of claim 8 wherein the fatty acid ester is
part of the phenolic resin component and is derived from an alcohol
having from 4 to 10 carbon atoms.
10. The binder system of claim 9 wherein the fatty acid ester is
the butyl ester of tall oil fatty acids.
Description
CLAIM TO PRIORITY
[0001] This application is a continuation application of U.S.
application Ser. No. 9/806,864 filed on Jul. 9, 2001. Applicants
claim priority to PCT/EP99/08419 filed on Nov. 4, 1999, DE 198 50
833 filed on Nov. 4, 1998, and U.S. application Ser. No. 9/806,864
filed on Jul. 9, 2001.
FIELD OF THE INVENTION
[0002] This invention relates to a binder system comprising a
phenolic resin component and an isocyanate component, wherein the
phenolic resin component comprises (a) an alkoxy-modified phenolic
resole resin and (b) an oxygen-rich polar, organic solvent, and a
process for preparing molds and cores with the binder system.
BACKGROUND OF THE INVENTION
[0003] A well-known and commercially successful method for
preparing foundry cores and molds is the "Cold-Box-Process" or the
"Ashland-Process". According to this method, a two-component
polyurethane binder system is used for the bonding of sand. The
first component consists of a solution of a polyol, which contains
at least two OH groups per molecule. The second component is a
solution of an isocyanate having at least two NCO groups per
molecule. The curing of the binder system takes place in the
presence of a basic catalyst. Liquid bases can be added to the
binder system before the molding stage, in order to bring the two
components to reaction (U.S. Pat. No. 3,676,392). Another
possibility, according to U.S. Pat. No. 3,409,579, is to pass
gaseous tertiary amines through a shaped mixture of an aggregate
and the binder.
[0004] In both these patents, phenolic resins are used as polyols,
which are prepared through condensation of phenol with aldehydes,
preferably formaldehyde, in the liquid phase, at temperatures of up
to around 130.degree. C., in the presence of divalent metal
catalysts. The manufacture of such phenolic resins is described in
detail in U.S. Pat. No. 3,485,797. In addition to unsubstituted
phenol, substituted phenols, especially o-cresol and p-nonyl
phenol, can be used (for example, EP-A-1 83 782).
[0005] As additional reaction components, according to EP-B-0 177
871, aliphatic monoalcohols with one to eight carbon atoms can be
used to prepare alkoxylated phenolic resins. According to this
patent, the use of alkoxylated phenolic resins in the binder
results in binders that have a higher thermal stability.
[0006] As solvents for the phenolic components, mixtures of
high-boiling point polar solvents (for example, esters and ketones)
and high boiling point aromatic hydrocarbons are typically 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
eliminate or reduce the amount of aromatic solvents, as a result of
the use of fatty acid methyl esters. The fatty acid methyl esters
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.
[0007] In practice, however, binder systems formulated according to
EP-A-0 771 599, display a serious disadvantage. They produce smoke
during the casting process, so much that in many foundries, they
are not practical to use.
[0008] 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 little aromatic hydrocarbon solvent, but
produce cores with adequate tensile properties.
SUMMARY OF THE INVENTION
[0009] This invention relates to a binder system comprising a
phenolic resin component and an isocyanate component, wherein the
phenolic resin component comprises (a) an alkoxy-modified phenolic
resole resin and (b) an oxygen-rich polar, organic solvent. The
invention also relates to foundry mixes prepared with an aggregate
and the binder, a process for making cores and molds, and a process
for casting metals.
[0010] The binder system has a little or no odor and the exhibits a
low incidence of smoke during casting. The cores produced with the
binder exhibit good flexural strength, particularly good immediate
strength, and are easily released from the molding equipment.
DETAILED DESCRIPTION OF THE INVENTION
[0011] Selecting an alkoxy-modified phenolic resole 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 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. The addition of fatty acid ester
has a positive effect on the separation effect and on moisture
resistance.
[0012] 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 phenols are alkyl-substituted
phenols, aryl-substituted phenols, cycloalkyl-substituted phenols,
alkenyl-substituted phenols, alkoxy-substituted phenols,
aryloxy-substituted phenols and halogen-substituted phenols.
[0013] The above named substituents have 1 to 26, and preferably 1
to 12, carbon atoms. Examples of suitable phenols, in addition to
the especially preferred unsubstituted 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-dicyclohexylphenol, 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: 1
[0014] where A, B and C can be hydrogen, alkyl radicals, alkoxy
radicals or halogens.
[0015] 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 benzaldehyde. 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 aqueous form or as paraformaldehyde.
[0016] In order to prepare the phenolic resole resins, a molar
ratio aldehyde to phenol of at least 1.0 should be used. 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.
[0017] In order to obtain alkoxy-modified phenolic resins, primary
and secondary aliphatic alcohols are used having 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.
[0018] 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 aldehyde 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.
[0019] The ratio of alcohol to phenol influences the properties of
the resin as well as the speed of the reaction. Preferably, the
molar ratio of alcohol to phenol amounts to less than 0.25. A molar
ratio of from 0.18-0.25 is most preferred. If the molar ratio of
alcohol to phenol amounts to more than 0.25, the moisture
resistance decreases.
[0020] Suitable catalysts are divalent salts of Mn, Zn, Cd, Mg, Co,
Ni, Fe, Pb, Ca and Ba. Zinc acetate is preferred.
[0021] 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
--(CH.sub.2O).sub.nR. In this case R is the alkyl group of the
alcohol, and .sub.n is a small whole number in the range of 1 to
5.
[0022] All solvents, which are conventionally used in binder
systems in the field of foundry technology, can be used. It is even
possible to use aromatic hydrocarbons in large quantities as
essential elements in the solution, except that those solvents are
not preferred because of environmental considerations. 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 ether ester, glycol
diester, glycol diether, cyclic ketone, cyclic ester (lactone) or
cyclic carbonate.
[0023] Cyclic ketone and cyclic carbonate are preferred.
Dicarboxylic acid ester exhibits the formula
R.sub.1OOC--R.sub.2--COOR.sub.1, where R.sub.1, represents an
independent alkyl group with 1-12, and preferably 1-6 carbon atoms,
and R.sub.2 is an alkylene group with 1-4 carbon atoms. Examples
are dimethyl ester from carboxylic acids with 4 to 6 carbon atoms,
which can, for example, be obtained under the name dibasic ester
from DuPont. Glycol ether esters are binders with the formula
R.sub.3--O--R.sub.4--OOCR.sub.5, where R.sub.3 represents an alkyl
group with 1-4 carbon atoms, R.sub.4 is an alkylene group with 2-4
carbon atoms, and R.sub.5 is an alkyl group with 1-3 carbon atoms
(for example butyl glycolacetate), with glycol etheracetate being
preferred. Glycol diesters exhibit the general formula
R.sub.5COO--R.sub.4--OOCR.sub.5 where R.sub.4 and R.sub.5 are as
defined above and the remaining R.sub.5, are selected, independent
of each other (for example, propyleneglycol diacetate), with glycol
diacetate being preferred. Glycol diether is characterized by the
formula R.sub.3--O--R.sub.4--O--R.sub.3, where R.sub.3 and R.sub.4
are as defined above and the remaining R.sub.3 are selected
independent of each other (for example, dipropyleneglycol dimethyl
ether). 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.
[0024] 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 is preferably at least 50% by weight, more preferably at
least 55% by weight of the total solvents.
[0025] 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 mPas), 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
the low viscosity phenolic resins described herein, where the
dynamic viscosity is determined by 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 mPas. In 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 least 150 N/cm.sub.2 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).
[0026] The addition of fatty acid ester to the solvent of the
phenolic component leads 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.
[0027] Aliphatic mono alcohols with 1 to 12 carbons are
particularly suitable for the esterification of fatty acids.
Alcohols 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.
[0028] 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
component of the phenolic component amounts to less than 50% by
weight based upon the total amount of solvents in the phenolic
resin component. 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-decylesters of tall oil
fatty acids.
[0029] By using the alkoxy-modified phenolic resins described
herein, 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 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.
[0030] 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'-dicyclohexylmethanediis- ocyanate, 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.
[0031] 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, 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 140.degree. C. and
230.degree. 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.
[0032] In addition to the already mentioned components, the binder
systems can include conventional additives, like, for example,
silane (U.S. Pat. No. 4,540,724), drying oils (U.S. Pat. No.
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).
[0033] 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 .mu.m.
The average particle size of the aggregate should have between 100
and 300 .mu.m.
[0034] 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.
[0035] 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 15% 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.
[0036] 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 U.S. Pat. No. 3,409,579, can also be passed through
the founded piece.
[0037] The invention also relates to a process for preparing a
foundry shape by the no-bake process, which comprises (a) forming a
foundry mix with the binder and an aggregate, (b) forming a foundry
shape by introducing the foundry mix obtained from step (a) into a
pattern; (c) contacting the shaped foundry mix with a liquid
tertiary amine catalyst; and (d) removing the foundry shape of step
(c) from the pattern.
[0038] 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.
[0039] In a preferred implementation, silane with the general
formula therefor--(R'--O).sub.3--Si--R-- 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
(.gamma.-glycidoxypropyltrimethoxysilane), Union Carbide A-1100
(.gamma.-aminopropyl triethoxysilane), Union Carbide A-1120
(N-.beta.-(aminoethyl)-.gamma.-amino-propyltrimethoxysilane) and
Union Carbide A1160 (ureidosilane).
[0040] If applicable, other additives can be used, including
wetting agents and sand mixture extending additives (English
Benchlife-additives), such as those in U.S. Pat. No. 4,683,252 or
U.S. Pat. No. 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.
[0041] The invention is further clarified by the following
examples.
EXAMPLES
[0042] If not otherwise specified, all percentages are by
weight.
[0043] 1. Manufacture of Phenolic Resins
[0044] The raw materials in Table I are placed in a reaction vessel
fitted with reflux condenser, thermometer and agitator. The
temperature is raised uniformly, under agitation, to
105-115.degree. 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.degree.
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.
1TABLE I (Amounts of components used to prepare comparison resin
and resin within the scope of the invention) Resin 1 2 not within
the scope of within the scope of the the invention invention Phenol
2130.7 g 1770.6 g Paraformaldehyde 91% 865.3 g 984.3 g n-butanol --
279.6 g Zinc acetate-dihydrate 1.0 g 1.5 g
[0045] 2. Manufacture of Phenolic Resin Solutions
[0046] With the phenolic resin manufactured according to the above
instructions, the solutions shown in Table II are manufactured.
Trade names are shown with an "H".
2TABLE II (Resin components prepared with comparison resin 1 that
is not within the scope of the invention) Resin Component 1A 1B 1C
1D Phenolic resin 1 67.5% 67.5% 67.5% 67.5% DBE (H).sup.1 19.0%
24.5% 27.0% 32% Forbiol 102 (H).sup.2 13.0% 7.5% 5.0% Silane 0.5%
0.5% 0.5% 0.5% Viscosity 2 phases 659 617 561 (mPas)
[0047] It is noteworthy that all of these formulations for the
phenolic resin component contain less than 40% by weight solvent
based upon the weight of the phenolic resin component.
3TABLE II (Continued) (Resin components prepared with resin that is
within the scope of the invention) Resin Component 2A 2B 2C 2D 2E
2F 2G 2H Phenolic resin 2 67.5% 67.5% 67.5% 67.5% 67.5% 67.5% 67.5%
67.5% DBE (H).sup.3 19.0% 24.5% 27.0% 32.0% BGA.sup.4 32.0%
EGD.sup.5 32.0% DPGME.sup.6 32.0% PPC.sup.7 32.0% Forbiol 102
(H).sup.8 13.0% 7.5% 5.0% Silane 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5%
0.5% Viscosity (mPas) 289 280 264 241 217 297 271 338 Phenolic
resin component 1A, separated into two phases after cooling down to
room temperature, and, for that reason, will not be examined
further. The viscosities of .sup.1DBE, dibasic ester, dimethyl
ester mixture of dicarbonic acids with 4 to 6 carbon atoms
(Dupont). .sup.2Forbiol 102, butyl ester of tall oil fatty acids
(Arizona Chemical). .sup.3DBE, dibasic ester, dimethyl ester
mixture of dicarbonic acids with 4 to 6 carbon atoms (Dupont).
.sup.4Butyl glycol acetate. .sup.5Ethylene glycol diacetate.
.sup.6Dipropylene glycol dimethyl ether. .sup.7Propylenecarbonate.
.sup.8Forbiol 102, butyl ester of tall oil fatty acids (Arizona
Chemical).
[0048] phenolic resin components 1B-1D are outside the favorable
range for technical applications, which is up to around 400 mPas.
On the other hand, there was no phase separation of the phenolic
resin components 2A-2H prepared with the phenolic resin 2 (within
the scope of the invention) and the viscosities of these phenolic
resin components were acceptable.
[0049] 3. Manufacture of polyisocyanate solutions Table III shows
the polyisocyanate components used in the binder systems.
4TABLE III (Composition of polyisocyanate components) Example 3A 3B
3C MDI.sup.9 80% 80% 80% Forbiol 102 (H) 19.8% 10% Forbiol 152
(H).sup.10 19.8% Solvesso 100 (H).sup.11 9.8% Acid chloride 0.2%
0.2% 0.2%
[0050] .sup.9 Technical diphenyl methane diisocyanate. .sup.10
Forbiol 152, mixture of octyl decylester of tall oil fatty acids
(Arizona Chemical). .sup.11 Solvesso 100, mixture of aromatic
hydrocarbons (Exxon).
[0051] 4.) Manufacture and testing of the aggregate/binder mixture:
Test cores were prepared as follows:
[0052] Into a laboratory mixer, 0.8 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. With this mixture, test cores 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).
[0053] The flexural strength of the test bodies is 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 after manufacturing them. The
results are shown in Table IV. Tests 1-3 were conducted with
binders using resin components containing comparative phenolic
resole resin 1 and are outside the scope of the invention. Tests
4-13 were conducted with binders using resin components containing
phenolic resole resin 2 and are within the scope of this
invention.
5 TABLE IV Test 1 2 3 4 5 6 7 8 9 10 11 12 13 RC.sup.12 1B 1C 1D 2A
2B 2C 2D 2E 2F 2G 2H 2D 2D PIC.sup.13 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A
3A 3B 3C Strength (N/cm.sup.2) Immediate 105 120 140 205 235 225
205 225 200 230 180 190 210 1 hr 380 355 390 555 575 565 580 560
555 530 430 580 500 2 hr 400 405 400 555 575 565 580 560 570 590
440 585 530 24 hr 555 540 530 590 630 610 590 570 570 600 550 590
570
[0054] .sup.12 Resin component used from Table II. .sup.13
Polyisocyanate component used from Table III.
[0055] The data in Table IV indicate the following:
[0056] Cores made with binders using conventional phenolic resins
(Comparative Tests 1-3) have lower initial strengths than those
binder systems that use phenolic resin components within the scope
of the invention (Tests 4-13). Also, the increase in strength over
time is slower.
[0057] The strengths of cores, particularly, the immediate
strengths, of all the cores made with binders within the scope of
the invention (Tests 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.
[0058] Both the fatty acid butyl ester and the fatty acid
octyl/decyl ester are equally suitable as solvents for the binders
within the scope of this invention (Tests 7 and 12). The use of
aromatic solvents is just as feasible (Tests 7 and 13).
[0059] 5. Observation of smoke development GF-test bars are kept in
the oven 1 minute at 650.degree. 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).
[0060] The results are shown in Table V.
6TABLE V (Smoke generation tests using cores made from binders
within the scope of the invention) Cores from Tests Described in
Table IV 4 5 6 7 8 9 10 11 12 RC 2A 2B 2C 2D 2E 2F 2G 2H 2D PIC 3A
3A 3A 3A 3A 3A 3A 3A 3B Value 10 8 8 5 5 5 5 5 5
[0061] The data in Table V indicate that the development of smoke
is less if the fatty acid (Forbiol 102) is reduced in favor of
oxygen-rich solvents. Casting tests with cores, which correspond to
those prepared for Test 4 (containing the fatty acid ester), and
those prepared with Test core 7 (no fatty acid) confirm this.
* * * * *