U.S. patent application number 12/028616 was filed with the patent office on 2009-08-13 for sulfur dioxide-cured epoxy acrylate foundry binder system.
This patent application is currently assigned to HA-INTERNATIONAL, LLC. Invention is credited to David Horstman, Sudhir Trikha, Doug Trinowski.
Application Number | 20090199992 12/028616 |
Document ID | / |
Family ID | 40937888 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090199992 |
Kind Code |
A1 |
Trinowski; Doug ; et
al. |
August 13, 2009 |
SULFUR DIOXIDE-CURED EPOXY ACRYLATE FOUNDRY BINDER SYSTEM
Abstract
The present invention provides an epoxy acrylate foundry binder
composition having an epoxy resin component (Part 1) and an
acrylate component (Part 2) containing about 1% to less than about
6% by weight of a borate ester. The epoxy acrylate binders of the
present invention are useful in making foundry cores and molds in
that the addition of the borate ester increases hot strength of the
binder system. Also provided is a cold-box process for making sand
cores and molds using the epoxy acrylate binders cured by sulfur
dioxide vapor.
Inventors: |
Trinowski; Doug; (Rochester
Hills, MI) ; Trikha; Sudhir; (Naperville, IL)
; Horstman; David; (Naperville, IL) |
Correspondence
Address: |
DRINKER BIDDLE & REATH LLP;ATTN: PATENT DOCKET DEPT.
191 N. WACKER DRIVE, SUITE 3700
CHICAGO
IL
60606
US
|
Assignee: |
HA-INTERNATIONAL, LLC
Westmont
IL
|
Family ID: |
40937888 |
Appl. No.: |
12/028616 |
Filed: |
February 8, 2008 |
Current U.S.
Class: |
164/16 ; 523/139;
525/451 |
Current CPC
Class: |
B22C 1/162 20130101;
B22C 1/2266 20130101; B22C 1/222 20130101 |
Class at
Publication: |
164/16 ; 523/139;
525/451 |
International
Class: |
B22C 1/00 20060101
B22C001/00; B22C 9/00 20060101 B22C009/00 |
Claims
1. A sulfur dioxide-curable binder composition comprising: an epoxy
resin component including at least one epoxy resin and a free
radical initiator; and an acrylate component including at least one
acrylate and a boric acid ester, wherein the boric acid ester is
present in an amount of about 1% to less than about 6% by weight
based on the weight of the acrylate component.
2. The binder of claim 1 wherein the boric acid ester is a trialkyl
borate.
3. The binder of claim 2 wherein the trialkyl borate is a
tri(C.sub.2-C.sub.8)alkyl borate.
4. The binder of claim 3 wherein the tri(C.sub.2-C.sub.8)alkyl
borate is selected from the group consisting of triethyl borate,
tri-n-propyl borate, tri-isopropyl borate, tri-n-butyl borate,
tri-isobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate,
and tri-n-octyl borate.
5. The binder of claim 1 wherein the boric acid ester is present in
an amount of about 2% to about 4% by weight based on the weight of
the acrylate component.
6. The binder of claim 2 wherein the trialkyl borate is present in
an amount of about 2% to about 4% by weight based on the weight of
the acrylate component.
7. The binder of claim 6 wherein the weight/weight ratio of the
epoxy resin component to the acrylate component is from about 2:1
to about 1:1.
8. The binder of claim 1 wherein the acrylate component further
includes a phenolic resin.
9. A sulfur dioxide-curable binder composition comprising: an epoxy
resin component including at least one epoxy resin and a free
radical initiator; and an acrylate component including at least one
acrylate and tri-n-butyl borate, wherein tri-n-butyl borate is
present in an amount of about 1% to less than about 6% by weight
based on the weight of the acrylate component.
10. The binder of claim 9 wherein tri-n-butyl borate is present in
an amount of about 2% to about 4% by weight based on the weight of
the acrylate component.
11. The binder of claim 10 wherein the weight/weight ratio of the
epoxy resin component to the acrylate component is about 2:1.
12. The binder of claim 11 wherein the epoxy resin component
comprises an epoxy resin selected from the group consisting of
bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof.
13. The binder of claim 12 wherein the acrylate component comprises
an acrylate monomer.
14. The binder of claim 13 wherein the acrylate monomer is selected
from the group consisting of trimethylolpropane triacrylate,
hexanediol diacrylate, and mixtures thereof.
15. The binder of claim 14 wherein the acrylate component further
includes a phenolic urethane resin.
16. A sulfur dioxide-curable foundry mix comprising: aggregate; and
a binder including an epoxy resin component and an acrylate
component, the epoxy resin component including at least one epoxy
resin and a free radical initiator, and the acrylate component
including at least one acrylate and a boric acid ester, wherein the
boric acid ester is present in an amount of about 1% to less than
about 6% by weight based on the weight of the acrylate component;
and the binder being present in an amount from about 0.5% to about
2% based on the total weight of the foundry mix.
17. The foundry mix of claim 16 wherein the boric acid ester is a
trialkyl borate.
18. The foundry mix of claim 17 wherein the trialkyl borate is a
tri(C.sub.2-C.sub.8)alkyl borate.
19. The foundry mix of claim 18 wherein the
tri(C.sub.2-C.sub.8)alkyl borate is selected from the group
consisting of triethyl borate, tri-n-propyl borate, tri-isopropyl
borate, tri-n-butyl borate, tri-isobutyl borate, tri-sec-butyl
borate, tri-tert-butyl borate, and tri-n-octyl borate.
20. The foundry mix of claim 18 wherein the
tri(C.sub.2-C.sub.8)alkyl borate is tri-n-butyl borate.
21. The foundry mix of claim 16 wherein the boric acid ester is
present in an amount of about 2% to about 4% by weight based on the
weight of the acrylate component.
22. The foundry mix of claim 20 wherein tri-n-butyl borate is
present in an amount of about 2% to about 4% by weight based on the
weight of the acrylate component.
23. The foundry mix of claim 22 wherein the weight/weight ratio of
the epoxy resin component to the acrylate component is about
2:1.
24. The foundry mix of claim 23 wherein the epoxy resin component
comprises an epoxy resin selected from the group consisting of
bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof.
25. The foundry mix of claim 24 wherein the acrylate component
comprises an acrylate monomer.
26. The foundry mix of claim 25 wherein the acrylate monomer is
selected from the group consisting of trimethylolpropane
triacrylate, hexanediol diacrylate, and mixtures thereof.
27. The foundry mix of claim 16 wherein the acrylate component
further includes a phenolic resin.
28. A method of making a foundry shape, comprising the steps of:
(a) preparing a foundry mix by admixing aggregate and a binder
comprising an epoxy resin component including at least one epoxy
resin and an effective amount of a peroxide; and an acrylate
component including at least one acrylate and a boric acid ester,
wherein the boric acid ester is present in an amount of about 1% to
less than about 6% by weight based on the weight of the acrylate
component; and wherein the binder is present in an amount from
about 0.5% to about 2% based on the total weight of the foundry
mix; (b) shaping the foundry mix to a desired configuration to
provide a shaped foundry mix; and (c) curing the shaped foundry mix
with gaseous sulfur dioxide to provide a foundry shape.
29. The method of claim 28 wherein the boric acid ester is a
trialkyl borate.
30. The method of claim 29 wherein the trialkyl borate is a
tri(C.sub.2-C.sub.8)alkyl borate.
31. The method of claim 30 wherein the tri(C.sub.2-C.sub.8)alkyl
borate is selected from the group consisting of triethyl borate,
tri-n-propyl borate, tri-isopropyl borate, tri-n-butyl borate,
tri-isobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate,
and tri-n-octyl borate.
32. The method of claim 30 wherein the tri(C.sub.2-C.sub.8)alkyl
borate is tri-n-butyl borate.
33. The method of claim 32 wherein tri-n-butyl borate is present in
an amount of about 2% to about 4% by weight based on the weight of
the acrylate component.
34. The method of claim 33 wherein the weight/weight ratio of the
epoxy resin component to the acrylate component is about 2:1.
35. The method of claim 34 wherein the epoxy resin component
comprises an epoxy resin selected from the group consisting of
bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof.
36. The method of claim 35 wherein the acrylate component comprises
an acrylate monomer.
37. The method of claim 36 wherein the acrylate monomer is selected
from the group consisting of trimethylolpropane triacrylate,
hexanediol diacrylate, and mixtures thereof.
38. The method of claim 28 wherein the acrylate component further
includes a phenolic resin.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to improved epoxy acrylate
foundry binder compositions having an epoxy resin component and an
acrylate component useful in making sulfur dioxide (SO.sub.2)-cured
foundry cores and molds. More particularly, this invention relates
to the use of borate esters such as trialkyl borates in the
acrylate component of such foundry binder compositions to improve
hot strength and thus prevent erosion-related defects.
BACKGROUND OF THE INVENTION
[0002] An important process used in the foundry industry for making
metal parts is sand casting. In sand casting, disposable foundry
shapes, including molds and cores, are made by shaping and curing a
foundry mix. The foundry mix is a mixture of an appropriate
aggregate (typically sand) and an organic or inorganic binder. The
function of a binder is to bond the aggregate together to make
molds and cores.
[0003] One foundry process that is commonly used for making cores
and molds entails the use of sulfur dioxide (SO.sub.2) to cure the
epoxy acrylate binder system. This is a variant of the "cold-box"
process in which a mixture of a peroxide, an epoxy resin, a
multifunctional acrylate, and optional diluents and/or additives
are mixed with an aggregate and compacted into a pattern to give
the mixture a specific shape. The shaped mixture is contacted with
SO.sub.2 vapor (optionally diluted with nitrogen), by blowing the
SO.sub.2 into the pattern in which the shape is contained so that
the SO.sub.2 reacts with the peroxide to form an acid and free
radicals. The acid cures the epoxy resin and the free radicals cure
the multifunctional acrylate rapidly hardening the mixture to
produce the core or mold which can be used immediately in a foundry
core and/or mold assembly.
[0004] Although the binder composition can be added to the foundry
aggregate separately, it is preferable to package the epoxy resin
and free radical initiator (peroxide) as a "Part 1" and add this
package to the foundry aggregate first. The ethylenically
unsaturated material (acrylate) is then preferably added to the
foundry aggregate as the "Part 2," either alone or along with some
of the epoxy resin before curing with SO.sub.2 vapor.
[0005] Although SO.sub.2-curing has been used successfully in many
foundries, one of the weaknesses of SO.sub.2-cured epoxy acrylate
binder systems has been the lack of adequate erosion resistance.
Erosion occurs when molten high temperature metals (such as iron or
steel) contact the mold or core surfaces during the pouring process
and sand is dislodged at the point of contact. Such erosion occurs
because the binder does not have sufficient heat resistance, or
"hot strength," to maintain surface integrity until the pouring
process is complete. The resulting loose sand may be carried into
the mold cavity by the liquid metal, creating sand inclusions and
weak areas in the casting. Dimensional defects may also be created
on the surface of the casting caused by metal penetration into the
surface of the mold or core.
[0006] To correct this problem, foundries have historically
resorted to the use of refractory coatings to increase hot strength
thereby improving resistance to defects caused by impingement of
the high temperature metal on mold or core surfaces. For example,
core and mold assemblies or parts thereof are coated with a slurry
consisting of a high melting refractory oxide, a carrier, and
thixotropic additives. Once dried on the mold or core surface, the
coating helps prevent erosion in most cases. However, this approach
is messy, adds complexity to the sand casting process, and requires
expensive gas-fired, microwave, or radiant energy ovens to cure or
set the coating making it cost prohibitive and inefficient. In
addition, when the cores and/or molds are heated during the drying
process, the strength of the organic binder-to-aggregate bond may
be significantly weakened sometimes making handling of the hot
cores problematic and reducing productivity due to distortion or
cracking of the core or mold.
[0007] Thus, there is a need for an SO.sub.2-cured epoxy acrylate
binder system that can provide foundry shapes with adequate hot
strength during the casting process. If a way could be found to
make such a binder with increased thermal stability, it would show
increased hot strength properties such as increased collapsibility
time in a foundry core and would represent a useful contribution to
the art. Additionally, because the improved foundry shapes would be
more resistant to erosion, they could be used to cast metal
articles without coating the foundry shapes with refractory
materials.
SUMMARY OF THE INVENTION
[0008] In one embodiment of the present invention, there is
provided a sulfur dioxide-curable binder composition comprising an
epoxy resin component including at least one epoxy resin and a free
radical initiator and an acrylate component including at least one
acrylate and a boric acid ester. The boric acid ester is present in
the binder composition in an amount of about 1% to less than about
6% by weight based on the weight of the acrylate component. In a
preferred embodiment, the boric acid ester is a trialkyl borate. In
a more preferred embodiment, the trialkyl borate is
tri(C.sub.2-C.sub.8)alkyl borate.
[0009] In another embodiment, there is provided a sulfur
dioxide-curable foundry mix comprising aggregate and a binder
including an epoxy resin component (Part 1) and an acrylate
component (Part 2). The epoxy resin component includes at least one
epoxy resin and a free radical initiator, and the acrylate
component includes at least one acrylate and about 1% to less than
about 6% by weight of a boric acid ester, based on the weight of
the acrylate component. The binder will be used at a level of from
about 0.5% to about 2% based on the total weight of the foundry
mix. In a preferred embodiment, the boric acid ester is a trialkyl
borate. Preferred trialkyl borates include
tri(C.sub.2-C.sub.8)alkyl borates. A particularly preferred
trialkyl borate is tri-n-butyl borate.
[0010] In another embodiment, there is provided a cold-box method
of making a foundry shape by preparing a foundry mix by admixing
aggregate and a binder comprising an epoxy resin component
including at least one epoxy resin and an effective amount of a
peroxide and an acrylate component including at least one acrylate
and a boric acid ester. The boric acid ester will be present in an
amount of about 1% to less than about 6% by weight based on the
weight of the acrylate component and the binder will be present in
an amount from about 0.5% to about 2% based on the total weight of
the foundry mix. The resulting foundry mix is shaped to a desired
configuration to provide a shaped foundry mix. The resulting shaped
foundry mix is cured with gaseous sulfur dioxide to provide a
foundry shape for casting metal parts. In a preferred embodiment,
the boric acid ester is a trialkyl borate. In a more preferred
embodiment, the trialkyl borate is tri(C.sub.2-C.sub.8)alkyl
borate.
DETAILED DESCRIPTION OF THE INVENTION
[0011] In accordance with the present invention, it has now been
found that addition of esters of boric acid ("borate esters") such
as trialkyl borates to an epoxy acrylate binder composition
provides unexpected improvements in hot strength properties in
foundry cores and molds. The foundry binder system includes an
epoxy resin component (Part 1) and an acrylate component (Part 2).
The trialkyl borate is preferably added to the acrylate component
(Part 2) of the binder.
[0012] The term "alkyl," as used herein, refers to a monovalent
saturated straight or branched chain hydrocarbon, or a monovalent
saturated cyclic hydrocarbon, having the number of carbons
designated (i.e. C.sub.1-C.sub.8 means one to eight carbons).
Examples include: methyl, ethyl, n-propyl, isopropyl, n-butyl,
isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, n-hexyl,
n-octyl, n-decyl, n-dodecyl and cyclohexyl.
[0013] The term "aryl," as used herein, refers to a carbocyclic
aromatic system containing one or more rings (typically one, two or
three rings) wherein such rings may be fused. The aromatic rings
may be substituted with one or more substituents, for example,
alkyl. Examples include: phenyl, naphthyl, anthracyl, o-cresyl,
m-cresyl and p-cresyl.
[0014] Trialkyl and triaryl borates are organic boron compounds
that are derived from boric acid, specifically esters of boric acid
("borate esters"). Preferred trialkyl borates include
tri(C.sub.2-C.sub.8)alkyl borates. Representative useful
tri(C.sub.2-C.sub.8)alkyl borates are triethyl borate, tri-n-propyl
borate, tri-isopropyl borate, tri-n-butyl borate, tri-isobutyl
borate, tri-sec-butyl borate, tri-tert-butyl borate, and
tri-n-octyl borate. A particularly preferred trialkyl borate is
tri-n-butyl borate (TBB). Useful triaryl borates include triphenyl
borate, tri-o-cresyl borate, tri-m-cresyl borate and tri-p-cresyl
borate. These and other suitable boric acid esters may be used in
accordance with the present invention.
[0015] The borate esters used in the present invention must be
soluble in the acrylate component (Part 2).
[0016] Furthermore, the borate ester may be present in an amount
from about 1% to less than about 6% by weight, based on the weight
of the acrylate component (Part 2). In a preferred embodiment, the
borate ester is present in an amount from about 1% to about 5% by
weight, based on the weight of the acrylate component. In a more
preferred embodiment, the borate ester is present in an amount from
about 2% to about 4% by weight, based on the weight of the acrylate
component. In a particularly preferred embodiment, the borate ester
is a tri(C.sub.2-C.sub.8)alkyl borate. Higher use levels of certain
higher carbon borate ester compounds (e.g. tri-n-octyl borate) may
be required in certain applications, due to the corresponding
increase in molecular weight of these compounds.
[0017] The epoxy resin component (Part 1) contains at least one
epoxy resin. An epoxy resin is a resin having an epoxide group.
Examples of epoxy resins include (1) diglycidyl ethers of bisphenol
A, B, F, G and H, (2) epoxy novolacs, which are glycidyl ethers of
phenolic-aldehyde novolacs, and (3) mixtures thereof.
[0018] Epoxy resins (1) are made by reacting epichlorohydrin with
the bisphenol compound in the presence of an alkaline catalyst. By
controlling the operating conditions and varying the ratio of
epichlorohydrin to bisphenol compound, products of different
molecular weights can be made. Epoxy resins of the type described
above based on various bisphenols are available from a wide variety
of commercial sources.
[0019] Examples of epoxy novolac resins (2) include epoxy cresol
and epoxy phenol novolacs produced by reacting a novolac resin
(usually formed by the reaction of ortho-cresol or phenol and
formaldehyde) with epichlorohydrin, 4-chloro-1,2-epoxybutane,
5-bromo-1,2-epoxypentane, 6-chloro-1,3-epoxyhexane, and the like.
In addition, other epoxy resins made from phenolic resins such as
phenolic resoles or resitols, may be used. One useful epoxy novolac
is EPON.TM.154 (Hexion Specialty Chemicals, Inc., Houston,
Tex.).
[0020] Preferred levels of epoxy resins in the epoxy resin
component (Part 1) of the present invention are: Bisphenol A epoxy:
0-50% by weight, based on the weight of the epoxy resin component;
Bisphenol F epoxy: 0-70% by weight, based on the weight of the
epoxy resin component; and epoxy novolac: 0-25% by weight, based on
the weight of the epoxy resin component.
[0021] Drying oils may be used in the epoxy resin component (Part
1). Useful drying oils are glycerides of fatty acids which contain
two or more double bonds and can polymerize. Examples of some
natural drying oils include soybean oil, sunflower oil, hemp oil,
linseed oil, tung oil, oiticica oil and fish oils, and dehydrated
castor oil, as well as the various known modifications thereof
(e.g., the heat bodied, air-blown, or oxygen-blown oils such as
blown linseed oil and blown soybean oil). Also, esters of
ethylenically unsaturated fatty acids such as tall oil esters of
polyhydric alcohols such as glycerine or pentaerythritol or
monohydric alcohols such as methyl and ethyl alcohols can be
employed as the drying oil. One preferred ester is butyl ester of
tall oil fatty acid. If desired, mixtures of drying oils can be
employed.
[0022] The epoxy resin component (Part 1) must include a free
radical initiator. Preferably, the free radical initiator is a
peroxide and/or hydroperoxide. Further examples include ketone
peroxides, peroxy ester free radical initiators, alkyl oxides,
chlorates, perchlorates, and perbenzoates. Hydroperoxides
particularly preferred in the invention include t-butyl
hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide,
and the like. The organic peroxides may be aromatic or alkyl
peroxides. Examples of useful diacyl peroxides include benzoyl
peroxide, lauroyl peroxide and decanoyl peroxide. Examples of alkyl
peroxides include dicumyl peroxide and di-t-butyl peroxide.
[0023] The acrylate component (Part 2) contains at least one
acrylic resin ("acrylate"). Acrylic resins include acrylate
monomer, oligomer, polymer, or mixtures thereof, which contain
ethylenically unsaturated bonds. Examples of such materials include
a variety of mono functional, difunctional, trifunctional,
tetrafunctional and pentafunctional monomeric acrylates and
methacrylates. A representative listing of these monomers includes
alkyl acrylates, acrylated epoxy resins, cyanoalkyl acrylates,
alkyl methacrylates, cyanoalkyl methacrylates, and difunctional
monomeric acrylates. Other acrylates which can be used include
trimethylolpropane triacrylate, hexanediol diacrylate,
pentaerythritol tetraacrylate, methacrylic acid and 2-ethylhexyl
methacrylate, the first two compounds being particularly preferred.
Typical reactive unsaturated acrylic polymers, which may also be
used include epoxy acrylate reaction products,
polyester/urethane/acrylate reaction products, acrylated urethane
oligomers, polyether acrylates, polyester acrylates, and acrylated
epoxy resins. In addition, phenolic urethane resins or other
phenolic resins can be combined with the acrylates in the Part 2
component. A useful phenolic urethane resin is Sigma Cure 705 (HA
International LLC, Westmont, Ill.). Also, optionally an effective
amount of an epoxy resin may be used in the Part 2 component.
[0024] It will be apparent to those skilled in the art that other
additives such as antioxidants, silanes, silicones, benchlife
extenders, release agents, defoamers, wetting agents, etc. can be
added to the aggregate or to the foundry mix. Useful antioxidants
include butylated phenols and butylated cresols. Useful silanes
include, but are not limited to,
gamma-glycidoxypropyltrimethoxysilane,
gamma-ureidopropyltrialkoxysilane,
gamma-aminopropyltriethoxysilane, and the like. Generally the
additives are added directly to either one of Part 1 or Part 2, or
both, as appropriate, before admixture with aggregate. In this
manner either Part 1 or Part 2, or both, can be supplied ready for
use in making foundry cores and molds.
[0025] The epoxy acrylate binder system of this invention contains
an epoxy resin component (Part 1) and an acrylate component (Part
2). The weight/weight ratio of the epoxy resin component (Part 1)
to the acrylate component (Part 2) can range from about 3:1 to
about 1:2. In a preferred embodiment, the weight/weight ratio of
the epoxy resin component (Part 1) to the acrylate component (Part
2) ranges from about 2:1 to about 1:1.
[0026] Various types of aggregate and amounts of binder can be used
to prepare foundry mixes by methods well known in the art. The
aggregate materials commonly used in the foundry industry include
silica sand, lake sand, bank sand, construction aggregate, quartz,
chromite sand, zircon sand, or the like. Reclaimed sand may also be
used.
[0027] Sand sold under the product designation F-5574, available
from Badger Mining Corporation, Berlin, Wis., is useful in making
cores and molds of the embodiments of the present invention.
Likewise, sand sold under the product designation Wedron 530,
available from Wedron Silica, a division of Fairmount Minerals,
Wedron, Ill., is also useful. Incast 55 silica sand, available from
Unimin Corp., Oregon, Ill., may also be used. Sand sold under the
product designation Nugent 480, available from Nugent Sand Company,
Muskegon, Mich., may also be used. As known in the art, the sand
type, grain size and distribution will affect the strength
development of the bound aggregate.
[0028] In ordinary sand type foundry applications, the amount of
binder is generally no greater than about 5% by weight and
frequently within the range of about 0.5% to about 4% by weight
based upon the weight of the aggregate. It has been found that the
epoxy acrylate binder made in accordance with the present invention
is effective when present in an amount from about 0.5% to about 2%
by weight based on the total weight of the foundry mix. It should
be noted that, generally, high binder levels cause gas related
defects in castings as well as result in high emission of volatile
organic compounds.
[0029] The foundry mix is molded into the desired shape by ramming,
blowing, or other known foundry core and mold making methods into a
suitable core box or pattern. The shape is then cured by the
cold-box process, using vaporous sulfur dioxide as the curing
agent. The shaped article is preferably exposed to effective
catalytic amounts of 100 percent vaporous sulfur dioxide, although
minor amounts of a carrier gas such as nitrogen may also be used.
The exposure time of the sand mix to the gas is typically from 0.5
to 3 seconds. The flow rate of the sulfur dioxide gas is dependent,
of course, on the size of the shaped foundry mix as well as the
amount of binder contained therein. Sufficient sulfur dioxide is
passed through the shaped foundry mix to provide substantially
complete reaction between the epoxy resin components and the
acrylate components and to produce a cured foundry shape. The
sulfur dioxide gas is injected at ambient temperature and at a
pressure which can vary depending on the dimensions of the shape to
be manufactured. The pressure must be sufficient for the gas to be
dispersed uniformly throughout the entire bulk of the foundry shape
and to escape to the outside of the mold. The cured shaped article
can be purged of sulfur dioxide with an inert gas, such as
nitrogen.
[0030] The following examples further illustrate the invention.
They should not be construed as in any way limiting the scope of
the invention.
Test Procedure
[0031] Resins were tested for hot strength as described in the
examples below using the following procedure. 16.08 grams of Part 1
resin and 7.92 grams of Part 2 resin were coated on to 2000 grams
of Wedron 530 sand using a Hobart mixer at speed 2 for 90 seconds.
The resulting resin coated sand was used to make 11/8''
d..times.2'' ht. cylinder test specimens in a die, equipped to make
three test specimens at a time. The resin-coated sand was blown
into the die and cured by gassing with SO.sub.2 for three seconds,
followed by 15 seconds purge with nitrogen. The test specimens were
stored in a desiccator for 2 hours prior to testing in a Dietert
No. 785 Thermolab Dilatometer with the furnace equilibrated at
1800.degree. F. A test specimen was placed in the dilatometer and
subjected to a 50 psi compressive load. These conditions simulate
the core behavior under the ferrostatic pressure of molten metal.
The time it took for a test specimen to collapse was then measured.
The time taken for the test specimen to collapse is indicative of
its thermostability. Resins giving higher collapse times are
thermally stable and will improve hot strength and vice versa. Six
test specimens were tested in each instance and an average collapse
time of those six results is reported.
[0032] In the examples below, higher collapse times indicate higher
hot strength under core-making conditions. The collapse times are
directly proportional to hot strength, so a shorter collapse time
is indicative of poor hot strength.
EXAMPLE 1
[0033] Part 1 was prepared by mixing Bisphenol F type epoxy resin
(45.6 grams), 3.6 epoxy novolac resin (25 grams), butyl ester of
tall oil fatty acid (0.9 grams) and cumene hydroperoxide (28.5
grams). Part 2 was prepared by mixing Bisphenol A type epoxy resin
(19.85 grams), trimethylolpropane triacrylate (45.16 grams),
hexanediol diacrylate (34 grams), butylated cresol (0.09 grams) and
gamma-glycidoxypropyltrimethoxysilane (0.9 grams). Parts 1 and 2
were used in the test procedure above.
EXAMPLE 2
[0034] Part 1 was prepared as in Example 1. Part 2 was prepared as
in Example 1, except 2 grams of tri-n-butyl borate was substituted
for 2 grams of Bisphenol A type epoxy resin. The amount of
tri-n-butyl borate was 2% by weight based on the total weight of
Part 2.
EXAMPLE 3
[0035] Part 1 was prepared as in Example 1. Part 2 was prepared as
in Example 1, except 6 grams of tri-n-butyl borate was substituted
for 6 grams of Bisphenol A type epoxy resin. The amount of
tri-n-butyl borate was 6% by weight based on the total weight of
Part 2.
TABLE-US-00001 TABLE 1 Example No. Collapse Time, sec. 1 165 2 175
3 155
[0036] Table 1 demonstrates the improvements in hot strength
properties as shown by a 6% increase in collapse time using the
Example 2 binder in comparison to the cylinder test specimens of
Example 1, in which no borate is used. Higher collapse times
indicate higher hot strength under core-making conditions. In
contrast, the collapse time using the Example 3 binder decreased in
comparison to the cylinder test specimens of Example 1, which
indicates that the beneficial effect in this particular system
resulted when tri-n-butyl borate was used in an amount less than
about 6% by weight based on the total weight of Part 2.
EXAMPLE 4
[0037] Part 1 was prepared by mixing a Bisphenol A type epoxy resin
(12.5 grams), Bisphenol F type epoxy resin (45.6 grams), 3.6 epoxy
novolac resin (12.5 grams), butyl ester of tall oil fatty acid (0.9
grams) and cumene hydroperoxide (28.5 grams). Part 2 was prepared
by mixing a phenolic urethane cold-box resin "Sigma Cure 705"--a
product of HA International, Westmont, Ill. (19.85 grams),
trimethylolpropane triacrylate (45.16 grams), hexanediol diacrylate
(34 grams), butylated cresol (0.09 grams) and
gamma-glycidoxypropyltrimethoxysilane (0.9 grams). Parts 1 and 2
were used in the test procedure above.
EXAMPLE 5
[0038] Part 1 was prepared as in Example 4. Part 2 was prepared as
in Example 4, except 2 grams of tri-n-butyl borate was substituted
for 2 grams of Sigma Cure 705 resin. The amount of tri-n-butyl
borate was 2% by weight based on the total weight of Part 2.
EXAMPLE 6
[0039] Part 1 was prepared as in Example 4. Part 2 was prepared as
in Example 4, except 4 grams of tri-n-butyl borate was substituted
for 4 grams of Sigma Cure 705 resin. The amount of tri-n-butyl
borate was 4% by weight based on the total weight of Part 2.
TABLE-US-00002 TABLE 2 Example No. Collapse Time, sec. 4 154 5 186
6 181
[0040] Table 2 demonstrates the improvements in hot strength
properties as shown by increased collapse times using the Example 5
and 6 binders, of 21% and 18%, respectively, in comparison to the
cylinder test specimens of Example 4, in which no borate is used.
Higher collapse times indicate higher hot strength under
core-making conditions.
EXAMPLE 7
[0041] The resin from Example 1 and the resin from Example 5 were
compared using a standard casting erosion test: "Test Casting
Evaluation of Chemical Binder Systems," Tordoff et al., AFS
Transactions, 1980, Vol. 74, p. 152-153, developed by British Steel
Casting Research Association, which is hereby incorporated by
reference. In this test, molten iron at approximately 2580.degree.
F. was poured into a 1 inch diameter, 16 inch high sprue. The
molten metal then impinges on a molded sand surface inclined at 60
degrees. The metal was poured until the bottom cavity, which holds
about 60 pounds of metal, the wedge shaped section, and the sprue
were filled with molten metal. The assembly was allowed to cool and
the wedge shaped section was removed and the amount of erosion was
measured. A casting defect due to erosion appears as a protuberance
on the wedge shaped section. The area of the protuberance was
measured to determine the extent of the erosion. This test was run
on, in duplicate, using molds made with the resin of Example 1 and
the resin from Example 5 with the following results. The sand mix
used was Incast 55 silica sand, 1.2% total resin and a Part 1/Part
2 ratio of 2/1.
TABLE-US-00003 TABLE 3 Metal Temp. Erosion Area Average Erosion
Resin System (.degree. F.) (sq. in.) (sq. in.) Example 1-A 2584
3.52 Example 1-B 2593 3.67 3.60 Example 5-A 2593 1.28 Example 5-B
2565 0.4 0.84
[0042] This test showed that the resin system in Example 5,
containing the borate compound, had 77% less erosion than the resin
system in Example 1.
EXAMPLE 8
[0043] The resin system in Examples 1 and 5 were also tested in a
foundry situation on a casting where erosion always occurred.
Twenty four cores were made with each system, placed in molds, and
then poured with molten iron at 2700.degree. F. After cooling, the
castings were removed from the molds and examined for erosion. They
were rated either acceptable or scrap. Results are shown in Table
4.
TABLE-US-00004 TABLE 4 Resin System % Acceptable % Scrap Example 1
8.3 91.7 Example 5 57 43
[0044] The improved system of Example 5 reduced erosion in the
castings substantially. Furthermore, it was found that erosion on
the Example 5 system could be eliminated by brushing a small area
with a refractory coating, while in contrast the entire core had to
be coated with the Example 1 system.
EXAMPLE 9
[0045] If a resin system were prepared by substituting triethyl
borate for tri-n-butyl borate in either Example 5 or 6, it is
expected that a longer collapse time would result in comparison to
the cylinder test specimens of Example 4, in which no borate is
used. The amount of triethyl borate would be 2-4% by weight based
on the total weight of Part 2.
EXAMPLE 10
[0046] If a resin system were prepared by substituting tri-n-propyl
borate for tri-n-butyl borate in either Example 5 or 6, it is
expected that a longer collapse time would result in comparison to
the cylinder test specimens of Example 4, in which no borate is
used. The amount of tri-n-propyl borate would be 2-4% by weight
based on the total weight of Part 2.
EXAMPLE 11
[0047] If a resin system were prepared by substituting triisopropyl
borate for tri-n-butyl borate in either Example 5 or 6, it is
expected that a longer collapse time would result in comparison to
the cylinder test specimens of Example 4, in which no borate is
used. The amount of triisopropyl borate would be 2-4% by weight
based on the total weight of Part 2.
EXAMPLE 12
[0048] If a resin system were prepared by substituting triisobutyl
borate for tri-n-butyl borate in either Example 5 or 6, it is
expected that a longer collapse time would result in comparison to
the cylinder test specimens of Example 4, in which no borate is
used. The amount of triisobutyl borate would be 2-4% by weight
based on the total weight of Part 2.
EXAMPLE 13
[0049] If a resin system were prepared by substituting
tri-sec-butyl borate for tri-n-butyl borate in either Example 5 or
6, it is expected that a longer collapse time would result in
comparison to the cylinder test specimens of Example 4, in which no
borate is used. The amount of tri-sec-butyl borate would be 2-4% by
weight based on the total weight of Part 2.
EXAMPLE 14
[0050] If a resin system were prepared by substituting
tri-tert-butyl borate for tri-n-butyl borate in either Example 5 or
6, it is expected that a longer collapse time would result in
comparison to the cylinder test specimens of Example 4, in which no
borate is used. The amount of tri-tert-butyl borate would be 2-4%
by weight based on the total weight of Part 2.
EXAMPLE 15
[0051] If a resin system were prepared by substituting tri-n-octyl
borate for tri-n-butyl borate in either Example 5 or 6, it is
expected that a longer collapse time would result in comparison to
the cylinder test specimens of Example 4, in which no borate is
used. The amount of tri-n-octyl borate would be 2-4% by weight
based on the total weight of Part 2.
EXAMPLE 16
[0052] If a resin system were prepared by using any of 1% by
weight, 1.5% by weight, 5% by weight, or 5.8% by weight of
tri-n-butyl borate in Example 5 (all substituting for a
corresponding amount of Sigma Cure 705 resin), it is expected that
a longer collapse time would result in comparison to the cylinder
test specimens of Example 4, in which no borate is used. The amount
of tri-n-butyl borate would be 1% by weight, 1.5% by weight, 5% by
weight, and 5.8% by weight, respectively, based on the total weight
of Part 2.
[0053] Although the above examples are intended to be
representative of the invention, they are not intended to limit the
scope of the appended claims. It will be apparent to those skilled
in the art that modifications may be made therein without departing
from the spirit of the invention and the scope of the appended
claims.
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