U.S. patent application number 17/077435 was filed with the patent office on 2021-02-11 for use of amine blends for foundry shaped cores and casting metals.
This patent application is currently assigned to ARKEMA FRANCE. The applicant listed for this patent is ARKEMA FRANCE. Invention is credited to Diether KOCH, Jens MULLER, Jean-Claude ROZE, Pierre-Henri VACELET, Bruno VAN HEMELRYCK.
Application Number | 20210039158 17/077435 |
Document ID | / |
Family ID | 1000005164514 |
Filed Date | 2021-02-11 |
United States Patent
Application |
20210039158 |
Kind Code |
A1 |
VAN HEMELRYCK; Bruno ; et
al. |
February 11, 2021 |
USE OF AMINE BLENDS FOR FOUNDRY SHAPED CORES AND CASTING METALS
Abstract
An improved process is described for preparing foundry shapes by
a cold box process, for making cores and moulds and for casting
metals, carrying out as a curing catalyst system a blend comprising
at least two tertiary amines.
Inventors: |
VAN HEMELRYCK; Bruno;
(Chaponost, FR) ; VACELET; Pierre-Henri; (Saint
Marcel, FR) ; ROZE; Jean-Claude; (Gaillon, FR)
; MULLER; Jens; (Haan, DE) ; KOCH; Diether;
(Mettman, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARKEMA FRANCE |
COLOMBES |
|
FR |
|
|
Assignee: |
ARKEMA FRANCE
COLOMBES
FR
|
Family ID: |
1000005164514 |
Appl. No.: |
17/077435 |
Filed: |
October 22, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15991707 |
May 29, 2018 |
10828696 |
|
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17077435 |
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14853156 |
Sep 14, 2015 |
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15991707 |
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12523089 |
Feb 9, 2010 |
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PCT/EP08/50722 |
Jan 22, 2008 |
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14853156 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 15/00 20130101;
B22C 1/20 20130101; B22D 29/00 20130101; B22C 1/10 20130101; B22C
9/123 20130101; B22C 1/162 20130101; B01J 31/0237 20130101 |
International
Class: |
B22C 9/12 20060101
B22C009/12; B22C 1/16 20060101 B22C001/16; B01J 31/02 20060101
B01J031/02; B22C 1/10 20060101 B22C001/10; B22C 1/20 20060101
B22C001/20; B22D 15/00 20060101 B22D015/00; B22D 29/00 20060101
B22D029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2007 |
EP |
07100920.3 |
Claims
1. A catalyst for curing a composite resin composition comprising a
blend of at least two tertiary amines.
2. The catalyst of claim 1, wherein each amine is present in the
blend in an amount of not less than 10% by weight, and not more
than 90% by weight.
3. The catalyst of claim 1 wherein the blend comprises at least one
tertiary amine having 3 to 5 carbon atoms with at least one
tertiary amine having 6 to 10 carbons.
4. The catalyst of claim 1, wherein the amines are chosen from
trimethylamine, N-methylaziridine, dimethylethylamine (DMEA),
N-methylazetidine, N-ethylaziridine, diethylmethylamine (DEMA),
dimethylisopropylamine (DMIPA), dimethyl-n-propylamine (DMPA),
N-n-propylaziridine, N-iso-propylaziridine, N-ethylazetidine,
N-methylpyrrolidine, N,N,N',N'-tetramethyl diamino methane,
triethylamine (TEA), methylethyl-n-propylamine,
methylethyl-iso-propylamine, dimethyl-n-butylamine,
dimethyl-sec-butylamine, dimethyl-iso-butylamine,
dimethyl-tert-butylamine, N-ethylpyrrolidine, N-methylpiperidine,
hexamethylene tetramine, dimethyl piperazine, N,N,N',N'-tetramethyl
diamino ethane, dimethylpentylamines, methylethylbutylamines,
diethylpropylamines, dipropylmethylamines, N-propylpyrrolidines,
N-ethylpiperidine, dimethyl hexylamines, methylethylpentylamines,
diethylbutylamines, dipropylethylamines, N-butylpyrrolidines,
N-propylpiperidines, diethyl piperazine, dimethylheptylamines,
methylethylhexylamines, diethylpentylamines, tripropylamines,
N-pentylpyrrolidines, N-butylpiperidines, dimethyloctylamines,
methylethyl heptylamines, diethylhexylamines,
ethylpropylpentylamines, dipropylbutylamines or
N-pentylpiperidines.
5. The catalyst of claim 1, wherein the amines are chosen from
DMEA, DMIPA, DEMA, DMPA or TEA.
6. The catalyst of claim 1, wherein the blend of amines are chosen
from DMEA-DMIPA, DMEA-DEMA, DMEA/DMPA or DMEA-TEA.
7. The catalyst of claim 1, wherein the blend of amines are chosen
from 50/50 DMEA/DMIPA, 20/80 DMEA/DMIPA, 10/90 DMEA/DMIPA, 50/50
DMEA/DMPA, 20/80 DMEA/DMPA, 10/90 DMEA/DMPA, 50/50 DMEA/DEMA, 20/80
DMEA/DEMA, 10/90 DMEA/DEMA, 50/50 DMEA/TEA, 20/80 DMEA/TEA, 10/90
DMEA/TEA, 80/20 DMEA/TEA and 90/10 DMEA/TEA, preferably 20/80
DMEA/DMIPA, 20/80 DMEA/TEA or 80/20 DMEA/TEA.
8. A process for preparing a foundry shape by the cold box process,
which process comprises the following steps; (a) forming a foundry
mix with a binder and an aggregate, (b) forming a foundry shape by
introducing the foundry mix obtained from step (a) into a pattern,
(c) contacting the foundry shape with a curing catalyst comprising
a blend of at least two tertiary amines, in a liquid or a gaseous
form, optionally with an inert carrier, (d) hardening the foundry
shape into a hard, solid, cured shape, and (e) removing the
hardened foundry shape of step (d) from the pattern.
9. The process according to claim 8, wherein the inert carrier is
gaseous and chosen from nitrogen, air, carbon dioxide or mixtures
thereof.
10. The process according to claim 8, wherein the curing catalyst
further comprises up to 25% by weight of at least one additional
primary and/or secondary amine.
11. The process according to claim 8, wherein the curing catalyst
further comprises 0.2% by weight of water.
12. The process according to claim 8, wherein the blend is a
mixture of at least one tertiary amine having 3 to 5 carbon atoms
with at least one tertiary amine having 6 to 10 carbons.
13. The process according to claim 8, wherein the blend is chosen
from DMEA-DMIPA, DMEA-DEMA, DMEA/DMPA or DMEA-TEA.
14. The process according to claim 8, wherein the blend is chosen
from 50/50 DMEA/DMIPA, 20/80 DMEA/DMIPA, 10/90 DMEA/DM1PA, 50/50
DMEA/DMPA, 20/80 DMEA/DMPA, 10/90 DMEA/DMPA, 50/50 DMEA/DEMA, 20/80
DMEA/DEMA, 10/90 DMEA/DEMA, 50/50 DMEA/TEA, 20/80 DMEA/TEA, 10/90
DMEA/TEA, 80/20 DMEA/TEA and 90/10 DMEA/TEA, preferably 20/80
DMEA/DMIPA, 20/80 DMEA/TEA or 80/20 DMEA/TEA.
15. The process of claim 8 further comprising the step of hardening
the hardened foundry shape obtained from step (e).
16. The process of claim 8 further comprising the steps: (f)
pouring metal in the liquid state around said hardened foundry
shape; (g) allowing said metal to cool and solidify forming a
mounded article; and (h) separating the molded article and said
hardened foundry shape.
17. The process according to claim 8, wherein the curing catalyst
further comprises up to 10% by weight of at least one additional
primary and/or secondary amine.
18. The process according to claim 8, wherein the curing catalyst
further comprises up to 0.5% by weight of at least one additional
primary and/or secondary amine.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 15/991,707, filed May 29, 2018, allowed, which
is a continuation application of U.S. application Ser. No.
14/853,156, filed Sep. 14, 2015, abandoned, which is a continuation
of U.S. application Ser. No. 12/523,089, filed Feb. 9, 2010,
abandoned, which claims priority to International Application No.
PCT/EP2008/050722, filed Jan. 22, 2008, which claims priority to EP
Application No. 07100920.3, filed Jan. 22, 2007, the contents of
which applications are incorporated by reference herein, in their
entireties and for all purposes.
FIELD OF THE INVENTION
[0002] This invention relates to the use of amine blends as curing
agents for binder compositions useful in the foundry art for making
cores that harden at room temperature. It also relates to
combinations of foundry aggregates, such as sand and binder,
generally based on phenolic (phenol aldehyde) resins and
poly-isocyanates, which, on being formed into a coherent mass with
the aggregate in a mould, generally a steel mould, is capable of
being cured at room temperature by an amine blend used as curing
agent. The self-supported cores as obtained can be used in making
metal castings.
[0003] When the cured resins are based on both phenolic resins and
polyisocyanates, the above process utilized in foundries is named
Polyurethane Cold Box Process (PUCB).
[0004] According to this method, a two-component polyurethane
binder system is used for the bonding of sand. The first component
consists in a solution of at least one polyol, generally comprising
at least two OH groups per molecule. The second component is a
solution of at least one isocyanate having at least two NCO groups
per molecule.
BACKGROUND OF THE INVENTION
[0005] The use of tertiary amines as curing agents has long been
known in PUCB: see for example U.S. Pat. Nos. 3,429,848; 3,485,797;
3,676,392; and U.S. Pat. No. 3,432,457. Such tertiary amines are
sometimes utilized with metal salts and provide a fast curing of
phenol formaldehyde and poly-isocyanate resins at room temperature.
They can be added to the binder system before the moulding stage,
in order to bring the two components to reaction (U.S. Pat. No.
3,676,392) or they can pass in a gaseous form through a shaped
mixture of an aggregate and the binder (U.S. Pat. No.
3,409,579).
[0006] Generally 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-nonylphenol, can be
used (see for example EP-A-0 183 782).
[0007] 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.
[0008] 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.
[0009] Preferred tertiary amines (catalyst) used in curing
polyurethane cold box (PUCB) processes are trimethyl amine (TMA),
dimethyl ethyl amine (DMEA), dimethyl iso-propylamine (DMIPA),
dimethyl-n-propylamine (DMPA) and triethyl amine (TEA). All these
tertiary amines are taught in the art to be used individually.
[0010] The catalyst is usually introduced as a combination of one
inert gas and one amine, in the liquid or gaseous state. The
boiling point of the amine is preferably below 100.degree. C. to
permit evaporation and to achieve satisfactory concentration of
amine in the amine-inert gas mixture injected into the steel mould.
A boiling point below 100.degree. C. also helps to avoid
condensation of the amine when it contacts the steel moulds.
[0011] However, the boiling point of the amine must be preferably
high enough to facilitate handling of the amine. Trimethylamine
(TMA) is a gas at normal ambient temperature (boiling point (Bp)
2.87.degree. C.), which makes it difficult to handle. Other
drawbacks can be found with low boiling tertiary amines: the
well-known low boiling tertiary amine DMEA (Bp 37.degree. C.) has
undesirable organoleptic characteristics. In particular, it has a
strong ammonia odor. Furthermore, this amine is very easily
impregnated into skin and clothing, making a very unpleasant
working environment when it is used.
[0012] On the other hand, the 89.degree. C. boiling point of
triethylamine (TEA) is probably the highest practical boiling point
because TEA tends to condensate out of the gas mixture in the
piping which carries the amine-inert gas mixture to the steel mould
in winter, and in addition badly cured spots are found in sand
cores produced in the steel mould.
[0013] The molecular weight of the amine must be low enough to
permit ready diffusion of the amine through sand in the steel
mould, especially in the corners and edges of the mold. TEA, with
molecular weight of 101, is probably the highest molecular weight
amine permissible for the so-called Cold Process; it has a very low
odor intensity and very low amine smell but displays lower curing
ability than the tertiary amines with lower molecular weights (Mw)
and boiling points.
[0014] On an industrial point of view, tertiary amines containing 5
carbon atoms such as DMIPA (Mw 87, Bp 67.degree. C.) or DMPA (Mw
87, Bp 65-68.degree. C. or DEMA (Mw 87, Bp 65.degree. C.)
constitute good compromise tertiary amines in the field of
catalytic gassing agents for curing resins in cold box processes.
Tertiary amines containing 5 carbon atoms require less energy input
and lower gassing temperatures in PUCB equipment than TEA.
[0015] DMIPA has a better reactivity than TEA: 1 kg of DMIPA is
capable of curing approximately 1200 kg of sand/resin mixture,
whereas 1 kg of TEA is capable of curing only 900 kg of the same
sand/resin mixture. DMIPA is less odorant than the lighter tertiary
amine DMEA.
[0016] Despite all these known curing amine catalysts, there is
still a need to provide an improved catalysis to the cold box
process, i.e., a catalyst which hardens binding resins more quickly
than tertiary amines containing 5 or more carbons, and which does
not possess the strong, irritating, and itching ammonia odor
associated with tertiary amines containing 4 or 3 carbons such as
dimethylethylamine (DMEA) or trimethylamine (TMA).
SUMMARY OF THE INVENTION
[0017] The present invention therefore relates to a new type of
amine catalyst for cold box processes, said catalyst allowing a
modulation of reactivity and safer and easier handling during
use.
[0018] More precisely, the present invention first relates to the
use of a blend of at least two tertiary amines as catalyst for
curing a composite resin composition, especially for preparing a
foundry shape by the said cold box process.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The use of the present invention has many advantages, among
other a lower amount of the used curing blend of amines as compared
to the amount theoretically expected, and allows a modulation of
both properties of curing kinetics and safer handling and storage
(less odorant and less flammable catalyst), as compared to the
known catalysts used in the art, which only consist in one single
amine.
[0020] More particularly, the curing catalyst system used in the
present invention is a blend of at least two tertiary amines, each
displaying curing reactivity and/or odor difference from one
another. The blends of amines used in the invention allow a
modulation in reactivity.
[0021] Preferably the blend does not contain two C.sub.5 tertiary
amines. However, two C.sub.5 tertiary amines mixed with one or more
C.sub.3, C.sub.4 and/or C.sub.6-C.sub.10 amines are encompassed in
the present invention.
[0022] Generally, the blend comprises from 10 to 90 parts by weight
of any of the amines present in the catalytic mixture.
Advantageously, each amine is present in the blend in an amount of
not less than 10% by weight, and not more than 90% by weight.
[0023] Unless otherwise specified all percentages values in the
present description and claims are understood to be % by
weight.
[0024] The blend according to the use of the present invention is
preferably a mixture of at least one tertiary amine having 3 to 5
carbon atoms with at least one tertiary amine having 6 to 10
carbons. Each tertiary amine generally is a trialkylamine, each
alkyl group being linear, branched or cyclic, and two alkyl groups
possibly forming, together with the nitrogen atom to which they are
bonded, a cyclic group containing 2 to 9 carbon atoms, preferably 2
to 6 carbon atoms. The invention does not exclude tertiary amines
that contain a second, third or even fourth tertiary nitrogen
atom.
[0025] The tertiary amines used in the invention may be substituted
with functional groups, which do not interfere in the catalytic
action of the tertiary amines. As substitution functional groups of
the tertiary amines, mention may be made for example of hydroxyl
groups, alkoxy groups, amino and alkyl amino groups, ketoxy groups,
thio groups, silyl groups and the like.
[0026] All tertiary amines used in the present invention are known,
commercially available compounds, or may be easily prepared
according to known processes, or directly or indirectly from
processes disclosed in the scientific literature, patents, in the
Chemical Abstracts or on the Internet.
[0027] According to a preferred embodiment, the blends comprise at
least one amine having a low molecular weight with at least one
amine of higher molecular weight.
[0028] According to another embodiment, preferred blends comprise
at least one amine having a low boiling point with at least one
amine of higher boiling point.
[0029] According to still another embodiment, preferred blends
comprise at least one fast curing tertiary amine with at least one
less reactive tertiary amine.
[0030] In another embodiment, preferred blends comprise at least a
fast curing tertiary amine having a low molecular weight and a low
boiling point with at least a less reactive tertiary amine of
higher molecular weight and higher boiling point.
[0031] Through the use of such blends, curing of polyurethane
binder is less odorant and safer to handle and store, than when a
fast curing amine is applied alone, and faster and more complete
than with the use of a high boiling tertiary amine alone.
[0032] Examples of C.sub.3-C.sub.6 amines that can be used in the
present invention comprise:
[0033] C.sub.3 amines: trimethylamine, N-methylaziridine; [0034]
C.sub.4 amines: dimethylethylamine (DMEA), N-methylazetidine,
N-ethylaziridine, [0035] C.sub.5 amines: diethylmethylamine (DEMA),
dimethylisopropylamine (DMIPA), dimethyl-n-propylamine (DMPA),
N-n-propylaziridine, N-iso-propylaziridine, N-ethylazetidine,
N-methylpyrrolidine, N,N,N',N'-tetramethyl diamino methane, [0036]
C.sub.6 amines: triethylamine (TEA), methylethyl-n-propylamine,
methylethyl-iso-propylamine, dimethyl-n-butylamine,
dimethyl-sec-butylamine, dimethyl-iso-butylamine,
dimethyl-tert-butylamine, N-ethylpyrrolidine, N-methylpiperidine,
hexamethylene tetramine, dimethyl piperazine, N,N,N',N'-tetramethyl
diamino ethane, [0037] C.sub.7 amines: dimethylpentylamines,
methylethylbutylamines, diethylpropylamines, dipropylmethylamines,
N-propylpyrrolidines, N-ethylpiperidine, [0038] C.sub.5 amines:
dimethylhexylamines, methylethylpentylamines, diethylbutylamines,
dipropylethylamines, N-butylpyrrolidines, N-propylpiperidines,
diethyl piperazine, [0039] C.sub.9 amines: dimethylheptylamines,
methylethylhexylamines, diethylpentylamines, tripropylamines,
N-pentylpyrrolidines, N-butylpiperidines, [0040] C.sub.10 amines:
dimethyloctylamines, methylethylheptylamines, diethylhexylamines,
ethylpropylpentylamines, dipropylbutylamines,
N-pentylpiperidines.
[0041] Preferred amines for use in the blends according to the
present invention are DMEA, DMIPA, DEMA, DMPA and TEA.
[0042] Examples of preferred blends of tertiary amines for use in
the present invention are: DMEA-DMIPA, DMEA-DEMA, DMEA/DMPA and
DMEA-TEA. Preferred blends are (weight ratios): 50/50 DMEA/DMIPA,
20/80 DMEA/DMIPA, 10/90 DMEA/DMIPA, 50/50 DMEA/DMPA, 20/80
DMEA/DMPA, 10/90 DMEA/DMPA, 50/50 DMEA/DEMA, 20/80 DMEA/DEMA, 10/90
DMEA/DEMA, 50/50 DMEA/TEA, 20/80 DMEA/TEA, 10/90 DMEA/TEA, 80/20
DMEA/TEA and 90/10 DMEA/TEA, preferably 20/80 DMEA/DMIPA, 20/80
DMEA/TEA and 80/20 DMEA/TEA. Preferably, the blend contains from 10
to 30 parts by weight of DMEA.
[0043] Such blends lead to improved curing efficiency as compared
to the performance of the highest boiling amine in the catalytic
mixture for polyurethane cold box curing and for odor improvement
as compared to the odor carried by the lowest boiling component, if
used alone.
[0044] Unexpectedly, blends of DMEA-DEMA and blends of DMEA-TEA,
the composition of which preferably ranges from 10% to 50% by
weight of DMEA to the total of the amine blend, display a synergy
at curing; this curing synergy can be appreciated by measuring the
global amount of amines blend needed for a 100% curing of a
sand+binder mixture versus the theoretical amount of blend that is
expected by adding the optimized volumes for each amine modulated
by their abundance ratio in the blend.
[0045] Such a behavior is particularly advantageous because it
allows not only a better and immediate volatile organic compounds
(VOC) reduction as compared to other curing systems which do not
display such a synergy, but also presents other advantages such as
a faster curing than the one obtained with a high boiling and high
molecular weight tertiary amine when used as single curing
catalyst, and less pungent and clothe impregnating than the one
obtained with a low boiling and low molecular weight tertiary amine
when used as single curing catalyst.
[0046] Tertiary amine blends may be used in a liquid state or
preferably in a gaseous state and in any desired predetermined
concentration, alone or preferably in combination with an inert
carrier.
[0047] The inert gaseous carrier can be nitrogen or air, but carbon
dioxide, less expensive than nitrogen, is sometimes utilized.
[0048] It would not be outside the scope of the invention to use a
mixture comprising, in addition to the tertiary amines blend, up to
25%, and preferably up to 10% by weight (to the total weight of all
amines present in the blend) of at least one other, primary and/or
secondary amine. However, the amount of primary and/or secondary
amine in the amine blend is more preferably maintained at 0.5% by
weight or less.
[0049] The tertiary amine blend can also comprise small amounts of
water: the concentration of water in the blend is preferably kept
below 0.2% by weight.
[0050] The present invention also relates to a process for
preparing a foundry shape by the cold box process.
[0051] This process invention has many advantages, among other a
lower amount of the used curing blend of amines as compared to the
amount theoretically expected, and allows a modulation of both
properties of curing kinetics and safer handling and storage (less
odorant and less flammable catalyst), as compared to the known
catalysts used in the art, which only consist in one single
amine.
[0052] The invention thus relates to a process for preparing a
foundry shape by the cold box process, which process comprises the
following steps: [0053] (a) forming a foundry mix with the binder
and an aggregate, [0054] (b) forming a foundry shape by introducing
the foundry mix obtained from step (a) into a pattern, [0055] (c)
contacting the shaped foundry mix with a curing catalyst comprising
a blend of at least two tertiary amines, in a liquid or preferably
in a gaseous form, optionally with an inert carrier, [0056] (d)
hardening the aggregate-resins mix into a hard, solid, cured shape,
and [0057] (e) removing the hardened foundry shape of step (d) from
the pattern.
[0058] The binder system comprises at least one phenolic resin
component and at least one isocyanate component.
[0059] Phenolic resins are most generally manufactured by
condensation of phenols and aldehydes (Ullmann's Encyclopedia of
Industrial Chemistry, Bd. A19, pages 371 ff, 5th, edition, VCH
Publishing House, Weinheim). Substituted phenols and mixtures
thereof can also be used. All conventionally used substituted
phenols are suitable.
[0060] The phenolic binders are preferably 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 may
be substituted. There is no particular limitation on the choice of
the substituent, as long as the substituent does not negatively
influence the polymerization of the phenol and the aldehyde.
[0061] 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.
[0062] 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.
[0063] All aldehydes, which are traditionally used for the
manufacture of phenolic resins, can be used within the scope of the
invention. Examples of these are formaldehyde, acetaldehyde,
propionaldehyde, furfuraldehyde, and benzaldehyde.
[0064] 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.
[0065] In order to prepare the phenolic 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.
[0066] 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.
[0067] The manufacture of alkoxy-modified phenolic resins is
described for example 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.
[0068] 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.
[0069] Suitable catalysts are divalent salts of Mn, Zn, Cd, Mg, Co,
Ni, Fe, Pb, Ca and Ba. Zinc acetate is preferred.
[0070] 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 n is a small whole number in the range of 1 to 5.
[0071] 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.
[0072] Cyclic ketone and cyclic carbonate are preferred.
Dicarboxylic acid ester exhibits the formula
R.sub.1OOC--R.sub.2--COOR.sub.1, where the R.sub.1, independently
from one another, represent an 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.
[0073] 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, independently
of each other (for example, propyleneglycol diacetate), with glycol
diacetate being preferred.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] Suitable binder systems exhibit an immediate strength of at
least 150 N/cm.sup.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 (see for instance EP
771 599 or DE 43 27 292).
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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 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.
[0083] The use of the 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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 and 230.degree. C. However,
preferably no aromatic solvents are used.
[0089] 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.
[0090] In addition to the already mentioned components, the binder
systems can include one or more conventional additives, like, for
example, those chosen from among silanes (see for instance U.S.
Pat. No. 4,540,724), drying oils (U.S. Pat. No. 4,268,425) or
"Komplexbildner" (WO 95/03903).
[0091] 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 moulding compound. The moulding compound
contains an effective binding quantity of up to 15% by weight of
the binder system with respect to the weight of the aggregate.
[0092] 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).
[0093] In order to manufacture foundry-moulded 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 be between 100
.mu.m and 300 .mu.m.
[0094] 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.
[0095] 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.
[0096] 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.
[0097] In a preferred implementation, silane with the general
formula therefore --(R'--O).sub.3--Si--R-- is added to the moulding
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 having 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.
[0098] 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).
[0099] If applicable, other additives can be used, including
wetting agents and sand mixture extending additives (English
Benchlife-additives), such as those disclosed in U.S. Pat. No.
4,683,252 or 4,540,724. In addition, mould release agents like
fatty acids, fatty alcohols and their derivatives can be used, but
as a rule, they are not necessary.
[0100] The curing of the founded piece (i.e., binder+aggregate) is
carried out under conditions well known in the art, using, as
catalytic system, a blend of at least two tertiary amines as
hereinbefore described.
[0101] The present invention also relates to a process of casting a
metal, said process comprises: [0102] a) preparing a foundry shape
as described above in steps (a) to (e), [0103] b) pouring said
metal while in the liquid state into a round said shape; [0104] c)
allowing said metal to cool and solidify; and [0105] d) then
separating the molded article from the foundry shape.
[0106] The invention is now further illustrated by the following
examples, which are not intended to bring any limitation to the
present invention.
EXAMPLES
[0107] A test was firstly carried out for the measurement of the
optimized, i.e. minimum amount of, amine quantity of a single
tertiary amine (DMEA, DEMA or DMIPA) or a blend of tertiary amines
(DMEA-DEMA, DMEA-TEA) for full curing in order to show the
difference of reactivity.
[0108] The various resins used for this test are commercial resins
from Ashland-Avebene (Usine du Goulet-20, rue Croix du Vallot,
27600 St Pierre-la-Garenne, France) sold under the trade name
Avecure.RTM.; these resins are composed of a formo-phenolic resin
and of an isocyanate resin, in accordance with the present
description.
[0109] The catalytic behaviour of the tertiary amines in
polyurethane curing is assessed for each any resin: full curing of
a 1.870-1.880 kg cylinder (length 300 mm.times.diameter 70 mm) of
sand LA32+binder requires about 0.2-0.4 mL of DMEA, while it
requires up to almost 1 mL of DEMA and can require up to about 1.5
mL of TEA. While using blends of DMEA-DEMA or DMEA-TEA, the
following results are obtained:
Example 1
Blends of DMEA/DEMA
[0110] A fixed amount of sand+resins mixture with a predetermined
amount of resins per mass unit of sand (normally between 0.5 and 2%
by weight of each resin based on the amount of sand mixed) is
placed in a long cylindrical shaped mould, the amine is poured as
liquid ahead of the sand-resins cylinder in a U tube and a heated
stream of carrier gas (normally nitrogen) at a fixed and
predetermined rate is passed through the amine loaded U tubing.
[0111] The carrier gas stream brings the volatilized amine to the
cylinder filled with sand+binder during a fixed time. Test cores
were prepared as follows:
[0112] Into a laboratory mixer, 0.8 part by weight of the phenolic
resin solution and 0.8 part by weight of the polyisocyanate
solution are added to 100 parts by weight of sand LA32 (Silfraco),
in the order given, and mixed intensively for 3 minutes. 6 kg of
fresh sand are used for each resin to be cured. This quantity
allows 3 gassings of 1.870-1.880 kg of sand+binder for
repeatability sake.
[0113] The 3 gassings are made at 5.5 bars (static) equivalent to
4.8 bars (dynamic). 2 purgings of 10 seconds each are applied
between each gassing operation. Gassing itself lasts 10 seconds at
1.5 bars (dynamic). Carrier gas heater is adjusted to 75.degree.
C..+-.3.degree. C. except for TEA for which it was modified to
95.degree. C.
[0114] The optimum (lowest) volume for 100% curing for each amine
or blend of amine is obtained by increasing the volume of injected
amine(s) by steps of 0.05 mL from 0, until reaching the catalytic
volume for which no more sand is left free (100% curing, the
sand+binder test core is totally solidified).
[0115] Amine(s) optimized volumes have been converted to weights
required for full curing through usage of their corresponding
densities. The amines density was measured or checked from
literature on a densimeter Metier Toledo DA-100M. The density of
DMEA is 0.678, the one of DEMA is 0.706, density of TEA is
0.728.
[0116] The checking of density value of blends versus the predicted
one based on linear combination of individual density of each amine
of the composition have shown that no volume contraction intervenes
that could have accounted for lower volumes than expected at
application.
[0117] Table 1 indicates the amounts (in grams) of single tertiary
amine (DMEA or DEMA) and the amount of different DMEA/DEMA blends
required for a full curing core test as described above.
Theoretical masses (Theo. Mass) of blends needed for 100% test core
curing in Table 1 are calculated according to the following
equation:
Theo Mass=(ratio of DMEA.times.mass of DMEA alone needed for full
curing+ratio of DEMA.times.mass of DEMA alone needed for full
curing).
TABLE-US-00001 TABLE 1 Type of Resin Avecure .RTM. Avecure .RTM.
Avecure .RTM. Amine 333/633 331/631 363/663 Mass of DMEA required
for 100% curing 0.3051 0.339 0.2034 Mass of DEMA required for 100%
curing 0.5656 0.777 0.31815 Experimental Mass of 50/50 DMEA/DEMA
blend 0.38115 0.4158 0.2079 Theoretical Mass of 50/50 DMEA/DEMA
blend 0.43535 0.55835 2.260775 Experimental Mass of 20/80 DMEA/DEMA
blend 0.3861 0.5967 0.2808 Theoretical Mass of 20/80 DMEA/DEMA
blend 0.5135 0.68996 0.2952 Experiment Mass of 10/90 DMEA/DEMA
blend 0.45825 0.6345 0.282 Theoretical Mass of 10/90 DMEA/DEMA
blend 0.53955 0.73383 0.306675
[0118] From the results of Table 1, it can be easily seen that a
blend of DMEA-DEMA containing 10, 20 or 50% of DMEA is more
reactive than DEMA alone, as seen by lower quantities requested for
full curing in the case of blends.
[0119] The results given in Table 1 also indicate that for 10/90,
20/80 and 50/50 blends of DMEA/DEMA, the required global amount of
amines for full curing the test core is lower that the scheduled
one based on single amines, i.e. (ratio of DMEA.times.mass (g) of
DMEA alone needed for full curing+ratio of DEMA.times.mass (g) of
DEMA alone needed for full curing).
Example 2
Blends of DMEA/TEA
[0120] Theoretical masses (Theo. Mass) of blends needed for 100%
test core curing are calculated according to the following
equation:
Theo Mass=(ratio of DMEA.times.mass of DMEA alone needed for full
curing+ratio of TEA.times.mass of TEA alone needed for full
curing).
[0121] Table 2 indicates the amount of single tertiary amine (DMEA
or TEA) and the amount of different DMEA/TEA blends required for a
full test core curing as described above.
TABLE-US-00002 TABLE 2 Amine Mass (g) of Mass (g) of Experimental
Theoretical DMEA required for TEA required for mass (g) of 20/80
mass (g) of 20/80 Resin 100% curing 100% curing DMEA/TEA blend
DMEA/TEA blend Avecure .RTM. 0.3729 0.9464 0.612 0.8317 373/673
Avecure .RTM. 0.3051 1.456 0.936 1.22582 353/653 Avecure .RTM.
0.3051 1.456 0.792 1.22582 333/633 Avecure .RTM. 0.339 1.456 0.936
1.2326 331/631 Avecure .RTM. 0.2034 0.9464 0.36 0.7978 363/663
[0122] The results of Table 2 show that quantities of the 20/80
DMEA/TEA blend needed for a full curing of the test core are lower
than the quantity of TEA alone needed for a 100% curing.
[0123] The results of Table 2 also show that quantities of the
20/80 DMEA/TEA blend needed for a full curing of the test core are
lower than theoretical amounts of the 20/80 DMEA/TEA blend as
calculated by adding proportionally the optimized quantities of
individual amines when used alone.
* * * * *