U.S. patent application number 12/742551 was filed with the patent office on 2010-12-23 for bio-based binder system.
This patent application is currently assigned to UNIVERSITY OF NORTHERN IOWA RESEARCH FOUNDATION. Invention is credited to Shoshanna R. Coon, Ryan Jones, Mitchell Patterson, Andrew Simonson, Gerard R. Thiel, Ian Williams.
Application Number | 20100319874 12/742551 |
Document ID | / |
Family ID | 40639159 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100319874 |
Kind Code |
A1 |
Thiel; Gerard R. ; et
al. |
December 23, 2010 |
BIO-BASED BINDER SYSTEM
Abstract
A bio-based binder system for use in preparing foundry molds. In
a preferred embodiment, the system includes the use of a) a
polyermizable hydroxyl-containing component comprising a
saccharide, b) an isocyanate component, and c) a catalyst, and
preferably amine catalyst, component adapted to catalyze the
polymerization of a) and b), in the presence of a foundry aggregate
such as sand. The system can be used in any suitable manner,
including in either a cold box process or no bake process as
described herein.
Inventors: |
Thiel; Gerard R.; (Dysart,
IA) ; Coon; Shoshanna R.; (Shell Rock, IA) ;
Patterson; Mitchell; (Cedar Falls, IA) ; Simonson;
Andrew; (De Witt, IA) ; Williams; Ian; (Cedar
Rapids, IA) ; Jones; Ryan; (Grundy Center,
IA) |
Correspondence
Address: |
INTELLECTUAL PROPERTY GROUP;FREDRIKSON & BYRON, P.A.
200 SOUTH SIXTH STREET, SUITE 4000
MINNEAPOLIS
MN
55402
US
|
Assignee: |
UNIVERSITY OF NORTHERN IOWA
RESEARCH FOUNDATION
Cedar Falls
IA
|
Family ID: |
40639159 |
Appl. No.: |
12/742551 |
Filed: |
November 14, 2008 |
PCT Filed: |
November 14, 2008 |
PCT NO: |
PCT/US08/83597 |
371 Date: |
August 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60987947 |
Nov 14, 2007 |
|
|
|
Current U.S.
Class: |
164/526 ;
523/139; 527/301 |
Current CPC
Class: |
B22C 1/2273 20130101;
C08G 18/6484 20130101; B22C 1/26 20130101; C09J 175/04
20130101 |
Class at
Publication: |
164/526 ;
527/301; 523/139 |
International
Class: |
B22C 9/00 20060101
B22C009/00; C08G 18/00 20060101 C08G018/00; B22C 1/22 20060101
B22C001/22 |
Claims
1-11. (canceled)
12. A foundry mold for use in making a shaped metal article by
metal casting, the foundry mold comprising the combination of a
foundry aggregate and a binder comprising a polymer resin which is
substantially free of polymerized phenol aldehyde and which
comprises the reaction product, in the presence of the aggregate,
of: a saccharide component which is substantially underivatized, an
isocyanate component, and a catalyst component capable of
catalyzing the polymerization of the saccharide component and the
isocyanate component.
13. The foundry mold of claim 12, wherein the reaction product is
formed in the presence of water.
14. The foundry mold of claim 12, wherein the saccharide component
is selected from the group consisting of mono, di-, oligo-, and
polysaccharides, including mixtures thereof.
15. The foundry mold of claim 14, wherein the saccharide component
comprises a polysaccharide selected from the group consisting of
cellulose, levan, pullulan, corn syrup, and molasses.
16. The foundry mold of claim 12, wherein the reaction product
comprises about 10 to about 40 weight percent saccharide
component.
17. The foundry mold of claim 16, wherein the reaction product
comprises about 15 to about 20 weight percent saccharide
component.
18. The foundry mold of claim 12, wherein the saccharide component
includes a saccharide derivative.
19. The foundry mold of claim 12, wherein the reaction product
includes a co-polymerized non-saccharide polyol component.
20. The foundry mold of claim 19, wherein the non-saccharide polyol
component comprises a polyol selected from the group consisting of
ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, hexane
1,6-diol, 2methyl-1,3-propanediol, glycerol, mannitol, sorbitol,
diethylene glycol, triethylene glycol, polyethylene glycols,
polypropylene glycols, butylene, dibutylene, and polybutylene
glycols.
21. The foundry mold of claim 20, wherein the reaction product
comprises about 15 to about 25% non-saccharide polyol
component.
22. The foundry mold of claim 12, wherein the reaction product
comprises about 20 to about 70% by weight of an isocyanate
component comprising one or more isocyanates selected from the
group consisting of 2,4- and 2,6-diisocyanatotoluene (TDI) and
their derivatives, methylenediphenyl 4,4'-, 2,4- and
2,2'-diisocyanates (MDI) and their derivatives, polymeric MDI's
(PMDI), 1,5-naphthalene diisocyanate (NDI), 4,4',
4''-triisocyanatotriphenylmethane and bis(3,5-
diisocyanato-2-methylphenyl)methane, 1,6-hexamethylene diisocyanate
(HDI), and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl(isophorone)
isocyanate (IPDI).
23. The foundry mold of claim 12 wherein the catalyst component
comprises a tertiary amine catalyst.
24. The foundry mold of claim 12 wherein the catalyst component is
present in an amount sufficient to provide a foundry work time of
between about 1 and about 30 minutes.
25. The foundry mold of claim 24, wherein the catalyst component is
present in an amount sufficient to provide a foundry work time of
between about 4 and about 10 minutes.
26. The foundry mold of claim 12, wherein the saccharide component
is substantially free of volatile organic compounds and the
reaction product is formed in the presence of water.
27. The foundry mold of claim 26, wherein the saccharide component
is substantially free of aromatic solvents.
28. A process for making a foundry mold for use in making a metal
article by metal casting, the foundry mold having a predetermined
shape defining an open volume corresponding to the metal article to
be cast, the process comprising forming a mixture into the
predetermined shape, the mixture comprising: a foundry aggregate, a
saccharide component which is substantially underivatized, an
isocyanate component, and a catalyst component capable of
catalyzing polymerization of the saccharide component and the
isocyanate component to form a polyurethane binder, and allowing
the saccharide component, the isocyanate component and the catalyst
component to react to form the polyurethane binder, thereby forming
the foundry mold.
29. The process of claim 28, wherein the foundry aggregate, the
saccharide component, the isocyanate component and the catalyst
component are formed into the mixture and thereafter the mixture so
made is formed into said shape.
30. The process of claim 29, wherein the mixture contains
sufficient catalyst so that the foundry work time of the mixture is
between about 1 and about 30 minutes.
31. The process of claim 28, wherein the foundry aggregate, the
saccharide component and the isocyanate component are combined, the
composition so made is formed into said shape, and thereafter a
catalyst component comprising a tertiary amine gas is passed
through the shaped composition.
32. The process of claim 28, wherein the mixture contains
water.
33. The process of claim 28, wherein the saccharide component is
substantially free of volatile organic compounds.
34. The process of claim 33, wherein the saccharide component is
substantially free of aromatic solvents.
35. A process for making a foundry mold for use in making a metal
article by metal casting, the foundry mold having a predetermined
shape defining an open volume corresponding to the metal article to
be cast, the process comprising forming a mixture into the
predetermined shape, the mixture comprising: a foundry aggregate
selected from the group consisting of silica sand, lake sand,
zircon, olivine, chromite, and mullite, a saccharide component
which is substantially underivatized, the saccharide component
comprising a polysaccharide selected from the group consisting of
cellulose, levan, pullulan, corn syrup, and molasses, a
non-saccharide polyol component comprising a polyol selected from
the group consisting of ethylene glycol, 1,2-propylene glycol,
1,3-propylene glycol, hexane 1,6-diol, 2 methyl-1,3-propanediol,
glycerol, mannitol, sorbitol, diethylene glycol, triethylene
glycol, polyethylene glycols, polypropylene glycols, butylene,
dibutylene, and polybutylene glycols, an isocyanate component
comprising one or more isocyanates selected from the group
consisting of 2,4- and 2,6-diisocyanatotoluene (TDI) and their
derivatives, methylenediphenyl 4,4'-, 2,4- and 2,2'-diisocyanates
(MDI) and their derivatives, polymeric MDI's (PMDI),
1,5-naphthalene diisocyanate (NDI), 4,4',
4''-triisocyanatotriphenylmethane and
bis(3,5-diisocyanato-2-methylphenyl)methane, 1,6-hexamethylene
diisocyanate (HDI), and
3-isocyanatomethyl-3,5,5-trimethylcyclohexyl(isophorone) isocyanate
(IPDI), and a catalyst component capable of catalyzing
polymerization of the saccharide component and the isocyanate
component to form a polyurethane binder, and allowing the
saccharide component, the non-saccharide polyol, the isocyanate
component and the catalyst component to react to form the
polyurethane binder, thereby forming the foundry mold.
36. A process according to claim 35, wherein: the saccharide
component is present in an amount between about 5 to about 65
weight percent of the binder, the non-saccharide polyol component
is present in an amount between about 1 and about 60% by weight of
the binder, and the isocyanate component is present in an amount
between about 10 and about 80% by weight of the binder.
37. A process according to claim 35, wherein: the saccharide
component is present in an amount between about 10 to about 40
weight percent of the binder, the non-saccharide polyol component
is present in an amount between about 10 and about 50% by weight of
the binder, and the isocyanate component is present in an amount
between about 20 and about 70% by weight of the binder.
38. A process according to claim 35, wherein: the saccharide
component is present in an amount between about 15 to about 20
weight percent of the binder, the non-saccharide polyol component
is present in an amount between about 15 and about 25% by weight of
the binder, and the isocyanate component is present in an amount
between about 20 and about 70% by weight of the binder, and the
aggregate is present in an amount of at least about 70 weight
percent of the foundry mold.
39. A process for making a foundry mold for use in making a metal
article by metal casting, the foundry mold having a predetermined
shape defining an open volume corresponding to the metal article to
be cast, the process comprising forming a mixture into the
predetermined shape, the mixture comprising: a foundry aggregate
comprising silica sand, a saccharide component which is
substantially underivatized, the saccharide component comprising
corn syrup, a non-saccharide polyol component comprising
triethylene glycol, an isocyanate component comprising one or more
methylenediphenyl 4,4'-, 2,4- and 2,2'-diisocyanates (MDI) and
their derivatives, and a catalyst component capable of catalyzing
polymerization of the saccharide component and the isocyanate
component to form a polyurethane binder, and allowing the
saccharide component, the non-saccharide polyol, the isocyanate
component and the catalyst component to react to form the
polyurethane binder, thereby forming the foundry mold, wherein: the
saccharide component is present in an amount between about 15 to
about 20 weight percent of the binder, the non-saccharide polyol
component is present in an amount between about 15 and about 25% by
weight of the binder, and the isocyanate component is present in an
amount between about 20 and about 70% by weight of the binder, and
the mixture contains sufficient catalyst so that the foundry work
time of the mixture is between about 1 and about 30 minutes, and
the aggregate is present at least about 70 weight percent of the
foundry mold.
Description
TECHNICAL FIELD
[0001] This invention relates to urethane forming foundry binders,
and mixes prepared with these binders.
BACKGROUND OF THE INVENTION
[0002] Conventional foundry binders include both a phenol
formaldehyde component and an organic polyisocyanate component.
Foundry mixes are prepared by mixing the binder with a foundry
aggregate. Foundry shapes (molds and cores) are typically prepared
by shaping the mix and curing the foundry shape with a liquid or
gaseous tertiary amine curing catalyst.
[0003] One of the major processes used in the foundry industry for
making metal parts is sand casting. In sand casting, disposable
foundry shapes (usually characterized as molds and cores) are made
by shaping and curing a foundry mix which is a mixture of sand and
an organic or inorganic binder. The binder is used to strengthen
the molds and cores.
[0004] One of the processes used in sand casting for making molds
and cores is the "cold-box" process. In this process a gaseous
curing agent is passed through a compacted shaped mix to produce a
cured mold and/or core. An alternative process is the "no bake"
method, that involves the use of liquid catalysts such as tertiary
liquid amines.
[0005] A phenolic-urethane binder system commonly used in the
cold-box process is cured with a gaseous tertiary amine catalyst.
See for example, U.S. Pat. Nos. 3,409,579, 3,429,848, 3,432,457,
and 3,676,392. The phenolic-urethane binder system usually consists
of a phenolic resin component and poly-isocyanate component which
are mixed with sand prior to compacting and curing to form a
foundry mix. Such phenolic-urethane binders used in the cold-box
process, have proven satisfactory for casting such metals as iron
or steel which are normally cast at temperatures exceeding about
1400 C. They are also useful in the casting of light-weight metals,
such as aluminum, which have melting points of less than 800 C.
[0006] There are disadvantages to using phenolic-urethane binders
in the cold-box process. Both the phenolic resin component and
polyisocyanate component generally contain a substantial amount of
organic solvent which can be obnoxious to smell. Additionally,
these binders contain small amounts of free formaldehyde and free
phenol which may be undesirable. Because of this, there is an
interest in developing binders which do not use organic solvents
and do not contain free formaldehyde or free phenol. Additionally,
when the two components of the phenolic-urethane binder system are
mixed with the sand to form a foundry mix, they may prematurely
react prior to curing with the gaseous catalyst. If this reaction
occurs, it will reduce the flowability of the foundry mix when it
is used for making molds and cores, and the resulting molds and
cores will have reduced strengths.
SUMMARY OF THE INVENTION
[0007] The present invention provides a novel bio-based binder
system for use in preparing foundry molds. In a preferred
embodiment, the system includes the use of a) a polymerizable
hydroxyl-containing component ("PHCC") comprising a saccharide, b)
an isocyanate component, and c) a catalyst, and preferably tertiary
amine catalyst, component adapted to catalyze the polymerization of
a) and b), whereby a) and b), and c) as well, if included and used
as a liquid, can be provided in a solvent-diluted system that can
be mixed with and cured in the presence of a foundry aggregate such
as sand. The system of this invention can be used in any suitable
manner, including in either a cold box process or no bake process
as described herein.
[0008] The binder system of this invention can be used to replace,
in whole or in part, conventional phenolic based binder systems. In
turn, a preferred binder system of this invention is substantially
free of formaldehyde or phenols, and preferably contains little or
no aromatic solvents. When reactive solvents or no solvents are
used, there are no volatile organic compounds (VOC's) present in
the binder system. Thus, the compositions of this invention are
environmentally attractive.
[0009] In another aspect, the invention provides
saccharide-containing PHCC compositions that are adapted (e.g., in
either chemical and/or physical ways) for use in preparing a binder
system of this invention, as well as kits and combinations that
include two or more of components a), b) and/or c), and that are
selected and used for preparing a binder system of this invention.
In turn, such a kit or combination preferably provides the
components in actual and relative amounts and/or concentrations
adapted for their use.
DETAILED DESCRIPTION
[0010] In one embodiment, the binder system of this invention
comprises a polymerizable hydroxyl-containing component (PHCC)
comprising a saccharide. Suitable saccharides are selected from
mono, di-, oligo-, and polysaccharides, alone or in solution with
other compounds, including derivatives and combinations
thereof.
[0011] A PHCC, as used in this invention, can include
monofunctional alcohols and polyols. Monofunctional alcohols
include, but are not limited to, aliphatic alcohols such as
methanol and ethanol. Polyols can include, but are not limited to,
saccharides. The term "polyol" in the present invention is defined
as a compound having at least two hydroxyl groups capable of
reacting with an isocyanate. As exemplified below, one preferred
non-saccharide polyol is ethylene glycol, a relatively simple
molecule having two hydroxyl groups. Without limiting the scope of
the invention, representative examples of other non-saccharide
polyols include 1,2-propylene glycol; 1,3-propylene glycol; hexane
1,6-diol; 2methyl-1,3-propanediol; glycerol; mannitol; sorbitol;
diethylene glycol; triethylene glycol; polyethylene glycols;
polypropylene glycols; and butylene, dibutylene, and polybutylene
glycols.
[0012] The non-saccharide PHCC's, if present, are preferably
present in the binder system in an amount ranging from about 1 to
about 60 weight percent of the system (i.e., combination of
whatever PHCC, isocyanate, liquid catalyst and solvent(s) may be
present), more preferably from about 10 to about 50 weight percent
of the system, and most preferably from about 15 to about 25 weight
percent of the system. Amounts of non-saccharide PHCC higher than
about 60 percent tend to require too much isocyanate component to
be economically viable, while amounts lower than about 1 percent
tend to not dissolve the saccharide to react effectively with the
isocyanate.
[0013] Saccharides are members of the carbohydrates family, a class
of molecules comprising polyhydroxy-aldehydes and
polyhydroxyketones. Saccharides range from relatively small, simple
monosaccharides such as glucose or fructose, to somewhat larger
oligosaccharides, such as hetero- or homopolymers of saccharide
units, to considerably larger, more complex polysaccharides such as
cellulose, levan, and pullulan. A common aspect of all saccharides
is the presence of multiple hydroxyl groups and at least one
aldehyde or ketone functionality.
[0014] A preferred saccharide of this invention is corn syrup, a
mixture of various chain length saccharides produced by hydrolyzing
the polysaccharides in corn starch. Corn syrup contains
aldohexoses, ketohexoses, and a number of other saccharides that
contain varying numbers of hydroxyl, aldehyde and ketone groups.
Yet another preferred saccharide source is molasses, e.g., either
from the sugar beet or cane molasses. Molasses is generally
referred to as the syrup that comes from the final crystallization
stage, with intermediate syrups being referred to as high green or
low green. Beet molasses is about 50% sugar by dry weight,
predominantly sucrose, but containing significant amounts of
glucose and fructose. The non-sugar content can include many ions
such as calcium, potassium, oxalate, and chloride.
[0015] The saccharide (e.g, in the form of corn syrup) may be used
in substantially unmodified form, or it may be physically altered
by removal of a substantial amount of the water in the syrup, or it
may be chemically altered by derivitization or caramelization.
Caramelization is the process of applying heat to a solution
containing saccharide, in order to remove water and melt the
saccharide. The caramelization process itself involves a complex
series of chemical reactions that can include, for instance,
condensation, decomposition, isomerization, fragmentation, and
polymerization reactions.
[0016] Other suitable saccharides include individual mono, di-,
oligo-, and polysaccharides as well as mixtures produced either
synthetically or from natural products such as vegetable starches
or bacterial or yeast fermentation. Furthermore, although the
present experiments utilized saccharides and saccharide mixtures
obtained from retail grocery stores or from corporate suppliers,
(Archer Daniels Midland for high fructose corn syrup, Montana
Polysaccharides for levan, and Hyashibara International for
pullulan), there is no reason to believe that the source of the
saccharides or mixtures is critical to the results obtained below.
Consequently, one of ordinary skill in the art will understand that
the present invention encompasses the use of mono, di-, oligo-, and
polysaccharides and mixtures and derivatives of them, irrespective
of source.
[0017] The one or more saccharides are preferably present in the
binder system in a total amount ranging from about 5 to about 65
weight percent of the binder, more preferably from about 10 to
about 40 weight percent of the binder, and most preferably from
about 15 to about 20 weight percent of the binder. Amounts of
saccharide lower than about 5 percent tend not to demonstrate
appreciable improvement in mechanical performance as compared to a
comparable composition lacking the saccharide, while amounts of
saccharide higher than about 65 weight percent of the binder tend
to consume too much isocyanate to be economically viable.
[0018] The binder system of this invention further comprises an
isocyanate component. Isocyanates useful in the current invention
include those that perform as suitable building blocks in
polyurethane chemistry such as aromatic, aliphatic, or
cycloaliphatic polyisocyanates having at least two active
isocyanate groups per molecule. Preferred isocyanates include
"Mondur 541", a commercially available diphenylmethane
diisocyanate, a polyisocyanate, and Rubinate (1780), a
water-compatible polyisocyanate based on diphenylmethane
diisocyanate, commercially available from Huntsman-ICI.
[0019] Without limiting the scope of the invention, representative
examples include 2,4-and 2,6-diisocyanatotoluene (TDI) and their
derivatives; methylenediphenyl 4,4'-, 2,4- and 2,2'-diisocyanates
(MDI) and their derivatives; industrial products which may
additionally comprise products having more than one ring (polymeric
MDI's or PMDI); 1,5-naphthalene diisocyanate (NDI);
4,4',4''-triisocyanatotriphenylmethane and bis(3,5-
diisocyanato-2-methylphenyl)methane; 1,6-hexamethylene diisocyanate
(HDI); and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl(isophorone)
isocyanate (IPDI). Many such isocyanates are available
commercially. Furthermore, basic polyisocyanates may also be
modified by bi- or trimerization to produce carbodiimides,
uretdiones, biurets, and allophanates.
[0020] The one or more isocyanates are preferably present in the
binder composition in an amount ranging from about 10 to about 80
weight percent of the binder, more preferably from about 20 to
about 70 weight percent of the binder, and most preferably from
about 25, and more preferably from about 30 to about 60 weight
percent of the binder.
[0021] The PHCC portion of the binder system may include solvents
in addition to the saccharide. These solvents may be reacting with
the isocyanate component, such as alcohols and non-saccharide
polyols, or nonreactive with isocyanate, such as an alkylene
carbonate, e.g., propylene carbonate, butylene carbonate, and the
like. The solvent(s) can be used, at least in part, to adjust the
viscosity of the binder system for its intended purpose, e.g., when
used with an aggregate, to adjust the viscosity to between about 50
centipoise (cps) and about 400 cps, and more preferably between
about 100 cps and about 300 cps.
[0022] Various types of aggregate and amounts of binder are used to
prepare foundry mixes by methods well known in the art. Ordinary
shapes, shapes for precision casting, and refractory shapes can be
prepared by using the binder systems and proper aggregate. The
amount of binder and the type of aggregate used is known to those
skilled in the art.
[0023] The preferred aggregate employed for preparing foundry mixes
is sand wherein at least about 70 weight percent, and preferably at
least about 85 weight percent, of the sand is silica. Other
suitable aggregate materials for ordinary foundry shapes include
zircon, olivine, aluminosilicate, chromite sand, and the like.
[0024] In ordinary sand type foundry applications, the amount of
binder system (including any PHCC, isocyanate, and if present
catalyst and solvent) is generally no greater than about 10% by
weight and frequently within the range of about 0.2% to about 5% by
weight based upon the weight of the aggregate. Most often, the
binder content for ordinary sand foundry shapes ranges from about
0.5% to about 2% by weight based upon the weight of the aggregate
in ordinary sand-type foundry shapes. The binder system of this
invention is preferably made available as a three part system with
the saccharide component in one package, the organic polyisocyanate
component in the second package, and the catalyst in the third
package. When making foundry mixes, usually the binder components
are combined and then mixed with sand or a similar aggregate to
form the foundry mix or the mix can be formed by sequentially
mixing the components with the aggregate. Preferably the
saccharide-containing PHCC and isocyanate are first mixed with the
sand before adding the catalyst component. Methods of distributing
the binder on the aggregate particles are well-known to those
skilled in the art. The mix can, optionally, contain other
ingredients such as iron oxide, ground flax fibers, wood cereals,
pitch, refractory flours, and the like.
[0025] The catalyst component of this invention preferably
comprises a tertiary amine catalyst, which can be provided in
either liquid (e.g., as in a "no bake" process) or gaseous form (as
in a cold box process), or both.
[0026] In a preferred embodiment, the process for preparing a
foundry shape by the coldbox process comprises:
[0027] (1) providing the ingredients needed to form a binder system
as described herein,
[0028] (2) mixing the ingredients with a foundry aggregate under
conditions suitable to then shape the foundry mix into a desired
core and/or mold;
[0029] (3) contacting the shaped foundry mix with a catalyst (e.g.,
gaseous tertiary amine catalyst); and
[0030] (4) removing the foundry shape of step (3) from the
pattern.
[0031] In a preferred "cold box" embodiment of this invention the
foundry mix (binder system and aggregate) can be molded into the
desired shape, whereupon it can be cured. Curing can be effected by
passing a tertiary amine gas through the molded mix such as
described in U.S. Pat. No. 3,409,579, hereby incorporated into this
disclosure by reference. Gassing times are dependent on core weight
and geometry and typically range from 0.5 to 30 seconds. Purge
times are dependent or core weight and geometry and typically range
from 1 to 60 seconds.
[0032] Metal castings are made by pouring molten metal into and
around an assembly of molds and/or cores made with the subject
binders and sand. In turn, using the cold box process, a preferred
process of casting a metal comprises:
[0033] (1) preparing a foundry core and/or mold as described
herein;
[0034] (2) providing and pouring metal while in the liquid state
into and around said shape;
[0035] (3) allowing the metal to cool and solidify; and
[0036] (4) then separating the molded article from the core or
mold.
[0037] Given the present description, those skilled in the art will
also appreciate the manner in which a binder system of this
invention can also be used to form molds using a no bake process.
In one such preferred embodiment, a binder system as described
herein, including a liquid catalyst, is provided and used to
contact a corresponding aggregate component to form a shaped core
and/or mold. The catalyst can be included in any suitable manner
and any suitable time, e.g., together with the PHCC component, at
the time of mixing any of the components of the binder system
together, or even after the combination of binder system with the
aggregate.
[0038] In turn, a preferred no bake method using the system of the
present invention can include:
[0039] (1) providing the ingredients needed to form a binder system
as described herein, providing and mixing at least the PHCC,
isocyanate and any solvents that may be used together in a
composition;
[0040] (2) including liquid catalyst in any suitable manner and
time, e.g., within one or more of the individual ingredients, or
adding it to the combination of ingredients prior to, during,
and/or after contact with the foundry aggregate;
[0041] (3) mixing the ingredients with a foundry aggregate under
conditions suitable to then shape and cure the foundry mix into a
desired core and/or mold;
[0042] (4) removing the foundry shape of step (3) from the
pattern.
[0043] A suitable liquid amine catalyst for use in such a process
is a base having a pKb value generally in the range of about 7 to
about 11. The term "liquid amine" is meant to include amines which
are liquid at ambient temperature or those in solid or gaseous form
which are dissolved in appropriate solvents. The pKb value is the
negative logarithm of the dissociation constant of the base and is
a well-known measure of the basicity of a basic material. The
higher this number is, the weaker the base. The bases falling
within this range are generally organic compounds containing one or
more nitrogen atoms. Specific examples of bases which have pKb
values within the necessary range include 4-alkyl pyridines wherein
the alkyl group has from one to four carbon atoms, isoquinoline,
arylpyridines such as phenyl pyridine, pyridine, acridine,
2-methoxypyridine, pyridazine, 3-chloro pyridine, quinoline,
N-methyl imidazole, N-ethyl imidazole, 4,4'-dipyridine,
4-phenylpropylpyridine, 1-methylbenzimidazole, and 1,4-thiazine.
Preferably used as the liquid tertiary amine catalyst is an
aliphatic tertiary amine, particularly [tris (3-dimethylamino)
propylamine].
[0044] In view of the varying catalytic activity and varying
catalytic effect desired, catalyst concentrations will vary widely.
In general, the lower the pKb value is, the shorter will be the
work time of the composition and the faster, more complete will be
the cure. In general, catalyst concentrations will be a
catalytically effective amount which generally will range from
about 0.1% to about 90% by weight of the PHCC component, preferably
0.2% by weight to 80% by weight based upon the PHCC component.
[0045] In a one embodiment of the invention, the liquid catalyst
level is adjusted to provide a work time for the foundry mix of 1
minute to 30 minutes, preferably 4 minutes to about 10 minutes, and
a strip time of about 1 minute to 30 minutes, preferably 5 minutes
to about 12 minutes.
[0046] Work time is defined as the time interval after mixing the
polyisocyanate, disaccharide, and catalyst and the time when the
foundry shape reaches a level of 45 on the Green Hardness "B" Scale
Gauge sold by Harry W. Dietert Co., Detroit, Mich. Striptime is
time interval after mixing the polyisocyanate, polyol, and catalyst
and the time when the foundry shape reaches a level of 90 on the
Green Hardness "B" Scale Gauge. The aggregate employed with the
catalyzed binder in producing the foundry mix should be
sufficiently dry so that a handleable foundry shape results after a
work time of 3 to 10 minutes and a strip time of 4 to 12 minutes.
The bench life of the foundry mix is the time interval between
forming the foundry mix and the time when the foundry mix is no
longer useful for making acceptable molds and cores.
[0047] A measure of the usefulness of the foundry mix and the
acceptability of the molds and cores prepared with the foundry mix
is the tensile strength of the molds and cores. If a foundry mix is
used after the bench life has expired, the resulting molds and
cores will have unacceptable tensile strengths. Because it is not
always possible to use the foundry mix immediately after mixing, it
is desirable to prepare foundry mixes with an extended bench life.
Many patents have described compounds which improve the bench life
of a phenolic-urethane foundry mix. Among the compounds useful to
extend the bench life of the foundry mix are organic and/or
inorganic phosphorus containing compounds.
[0048] Foundry shapes, including both foundry cores and molds, are
made by mixing the binder compositions of the present invention
with aggregates using mixing methods well known in the art. One
common method is to meter the PHCC component, isocyanate component,
and any catalyst into a foundry aggregate such as silica sand as it
goes through a high speed continuous mixer to form a foundry mix.
The foundry mix, i.e., the intimately mixed sand binder
composition, is placed in a pattern and allowed to cure at ambient
temperature. After curing, the self-supporting foundry shape can be
removed from the pattern. The foundry shapes, typically including
mold halves and any needed cores, are assembled to give a complete
mold into which molten metal can be poured. On cooling, a metal
casting having the shape of the sand mold is produced. Suitable
aggregate materials for foundry shapes include silica sand, lake
sand, zircon, olivine, chromite, mullite and the like.
[0049] Additives commonly used in the foundry art to improve
casting quality such as black iron oxide, red iron oxide, clay,
wood flour and the like may be incorporated into the foundry mix
compositions. Other optional ingredients that may be added to the
polyol component are adhesion promoters and release agents. Silane
coupling agents such as gamma-ureidopropyltriethoxysilane, and
gamma-aminopropyltrimethoxysilane may be added to increase tensile
strengths and improve humidity resistance. Release agents such as
glycerol trioleate and oleic acid may be added in small amounts to
improve release from mold patterns. Although not preferred, core
and mold coatings may be applied to the bonded sand cores and molds
of this invention to reduce erosion and improve casting finish in
difficult casting applications.
EXAMPLES
[0050] The following examples will serve to illustrate the
preparation of several foundry binder compositions within the scope
of the present invention. It is understood that these examples are
set forth for illustrative purposes and that many other
compositions are within the scope of the present invention. Those
skilled in the art will recognize that similar foundry binder
compositions may be prepared containing different quantities of
materials and equivalent species of materials than those
illustrated below. All parts are by weight unless otherwise
specified.
[0051] In the following experiments, commercial, food grade corn
syrup was tested with different concentrations of isocyanate resins
and additives. Although the data are not exhaustive, they will
illustrate to one skilled in the art that the corn syrup based
formulations consistently provided highly practicable work/strip
times and tensile strengths. As is known to those experienced in
the art, such times and tensile strengths may be suitable for a
significant range of applications without substantial
modification.
[0052] Four embodiments of the present invention were tested as
replacements for phenol formaldehyde in a foundry binder system.
These embodiments comprised two mixtures termed PH3 and PH4. The
mixture referred to as PH3 was composed of 72.6% saccharide (corn
syrup), 17.7% ethylene glycol, and 9.7% propylene carbonate. The
mixture referred to as PH4 was composed of 65.3% saccharide (corn
syrup), 15.9% ethylene glycol, 8.7% propylene carbonate, and 10%
water.
[0053] Sand was evenly coated with the PH3 component and then
combined with a commercially available isocyanates and solvent
mixture with an amine catalyst to form a phenolic urethane polymer
adhesive that acted as a foundry sand binder. Coating of the sand
consisted of mixing 3 kilograms of IC55 silica sand with 0.3% of
the PH3 component, 1.2% of commercially available isocyanate and
solvent mixture and 0.225% of a commercially available tertiary
amine catalyst in paddle type mixer. After the sand was coated
sufficiently the mixture was packed into the test coupon mold.
Tensile strength of the bonded sand test coupons was measured at 10
minutes, 1 hour, 3 hours, and 24 hours after the sand had cured.
Standard permeability, and scratch hardness tests were also
conducted. The testing procedure was repeated with the PH4 mixture.
Two isocyanates were evaluated and the results compared to a
commercially available phenolic urethane foundry binder.
[0054] Test Series A was comprised of 20% PH3 and 80% isocyanate A
(MDI based--diluted in solvent). The work time was 8 minutes and
the strip time was 12 minutes. Test series B was comprised of 20%
PH4, 80% Isocyanate A. The work time was 5.5 minutes and the strip
time was 7.5 minutes. Test Series C was comprised of 20% PH3 and
80% Isocyanate B (MDI based diluted in low VOC solvent). The work
time was 5.5 minutes and the strip time was 15 minutes. Test series
D was comprised of 20% PH3 and 80% Isocyanate C (MDI based--water
compatible). The work time was 3.5 minutes and the strip time was
4.5 minutes. Commercial baseline refers to a standard phenolic
urethane no bake system using 55% Pep Set 1000, 45% Pep Set 2000,
and 8% (binder weight) Pep Set 3500. The work time was 3.5 minutes
and the strip time was 4.25 minutes.
[0055] Through this testing we learned that small water additions
did not affect the tensile strength development of the binder
system and may actually aid in the ability to evenly coat the
aggregate, silica sand in this case. When combined with
commercially available MDI mixtures the saccharides yielded tensile
strength equal to or higher than a commercially available phenol
formaldehyde foundry binder. The tensile properties developed with
water compatible isocyanates were slightly lower than the
commercially available phenol formaldehyde foundry binder.
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