WO2001014083A1

WO2001014083A1 - Amine curable foundry binder containing an ester of certain organic acids

Info

Publication number: WO2001014083A1
Application number: PCT/US2000/020995
Authority: WO
Inventors: Robert B. Fechter; Laurence G. Dammann
Original assignee: Ashland Inc.
Priority date: 1999-08-19
Filing date: 2000-08-02
Publication date: 2001-03-01
Also published as: AU6617600A

Abstract

This invention relates to amine curable organic foundry binder compositions that contain an ester of certain organic acids, preferably organic acids having one or more monobasic acid groups, more preferably sulfonate esters and α-substituted carboxylate esters. Foundry mixes are prepared from the binder by mixing the binder with a foundry aggregate. The foundry binders and foundry mixes are used to make foundry shapes, e.g. molds and cores. The invention also relates to a method of preparing foundry shapes by the cold-box process, the shapes prepared, a method of making a metal casting, and metal castings by this process.

Description

AMINE CURABLE FOUNDRY BINDER CONTAINING AN ESTER OF CERTAIN ORGANIC ACIDS

FIELD OF THE INVENTION This invention relates to amine curable organic foundry binder compositions that contain an ester of certain organic acids, preferably organic acids having one or more monobasic acid groups, more preferably sulfonate esters and substituted carboxylate esters. Foundry mixes are prepared from the binder by mixing the binder with a foundry aggregate. The foundry binders and foundry mixes are used to make foundry shapes, e.g. molds and cores. The invention also relates to a method of preparing foundry shapes by the cold-box process, the shapes prepared, a method of making a metal casting, and metal castings by this process.

BACKGROUND OF THE INVENTION In the foundry industry, one of the procedures used for making metal parts is

"sand casting". In sand casting, disposable molds and cores are fabricated with a mixture of sand and an organic or inorganic binder. The foundry shapes are arranged in casting assembly, which results in a cavity through which molten metal will be poured. After the molten metal is poured into the assembly of molds and cores and cools, the metal part formed by the process is removed from the assembly. The binder is needed so the molds and cores will not disintegrate when they come into contact with the molten metal.

Two of the prominent fabrication processes used in sand casting are the no-bake and the cold-box processes. In the no-bake process, a liquid curing catalyst is mixed with an aggregate and binder to form a foundry mix before shaping the mixture in a pattern. The foundry mix is shaped by putting it into a pattern and allowing it to cure until it is self-supporting and can be handled. In the cold-box process, a gaseous curing catalyst is passed through a shaped mixture (usually in a corebox) of the aggregate and binder to cure the mixture. A binder commonly used in the cold-box fabrication process is a phenolic- urethane binder. The phenolic-urethane binder is mixed with an aggregate to form a foundry mix. The foundry mix is blown into pattern, typically a corebox, where it is cured by passing a gaseous tertiary amine catalyst through it. The phenolic-urethane binder consists of a phenolic resin component and polyisocyanate component. Phenolic-urethane binders are widely used in the foundry industry to bond the sand cores used in casting iron and aluminum. An example of a commonly used phenolic- urethane binder used in the cold-box process is disclosed in U.S. Patent 3,409,575. More recently amine curable cold-box binders based on acrylic-epoxy-isocyanate were developed, such as those shown in U.S. Patent 5,880,175, which is hereby incorporated by reference.

One of the problems with using organic binders to form foundry shapes is that they can be too effective in binding the aggregate together. The result is that the foundry shapes are not readily separated from the metal part formed during the casting process. Consequently, time consuming and labor intensive means must be utilized to break down the binder so the metal part can be removed from the casting assembly. This is particularly a problem with internal cores, which are imbedded in the casting assembly and not easily removed. The phenolic-urethane cold-box process can be used to make cores and molds for the casting of ferrous and non-ferrous metal parts. Since iron castings are manufactured at about 1500° C, any phenolic-urethane binder used in making foundry shapes, i.e. internal cores, will undergo rapid thermal decomposition at this temperature. Because of this, the internal core can be easily separated from the iron casting. This does not occur when aluminum parts are cast because aluminum castings are manufactured at about 700° C. At this lower temperature, the phenolic-urethane binder does not readily decompose when the aluminum is cast, thus making complete removal of an internal core difficult. Since light alloy casting, such as aluminum casting, is becoming increasingly used in place of iron as a means of reducing the weight of vehicle components such as engine blocks and manifolds, there is a need for developing new methods which facilitate the removal of internal cores.

One method of facilitating removal of an internal core from a large aluminum casting (e.g. an engine block) or a complex aluminum casting (e.g. a water pump housing), is by baking the casting in a forced air oven at a high temperature typically for four to ten hours until the binder slowly decomposes (thermal core removal). This procedure reduces productivity and requires forced air ovens and large amounts of energy. Alternatively, some aluminum castings can be violently shaken until the internal core is released (mechanical core removal or "shakeout"). This procedure is inefficient and also reduces productivity.

An approach taken to improve the shakeout of phenolic-urethane binders is shown in U.S. Patent 4,293,480. This patent discloses a binder containing a modified isocyanate component that promotes better shakeout. On the other hand, U.S. Patent 4,352,914 discloses a polyurethane binder with improved shakeout where the resin component is specified as a compound selected from the group consisting of (a) a polyol compound obtained by the reaction of formaldehyde with a compound selected from bisphenols, cyclic ketones in each of which both of the carbon atoms adjacent to the carbonyl group have a total of at least two hydrogen atoms, and mixtures thereof, and (b) a derivative of the polyol compound (a) which is a reaction product of a polyol compound (a) and a monohydric alcohol.

It is also known to add simple compounds to phenolic-urethane binders that will improve shakeout without affecting the stability of the binder. For instance, it is known to add polyester polyols ((U.S. Patent 4,982,781) and polyether polyols (U.S. Patent 5,132,339) to improve shakeout. The English translation of the abstract of Japanese Patent 57050585 discloses the use of organosulfonic acids (as well as carboxylic acids) in amine-cured phenolic-urethane binders for improved shakeout, while the English translated abstract of Russian application SU 79-2844061 indicates that sodium salts of certain organosulfonic acids can improve "knock-out" of foundry shapes made from certain inorganic binders.

Because of problems associated with the shakeout of foundry shapes made with phenolic-urethane, other cold-box binder systems are often used for casting aluminum that provide good core removal. For example, furan cold-box resins display excellent core removal characteristics in aluminum casting. However, furan resin binders build a tar like residue on tooling. This requires frequent cleaning, higher tooling costs, and lowers foundry productivity. See for instance U.S. Patent 3,879,339.

SUMMARY OF THE INVENTION

The invention relates to foundry binder composition comprising as a mixture: (a) an amine curable organic foundry binder selected from the group consisting of phenolic-urethane and epoxy-acrylic-isocyanate binders; and

(b) an effective amount of an ester of an acid wherein said acid used to form said ester

(i) has a pK_a of less than 3.0, preferably less than 1.0, and more preferably less than 0.8; and

(ii) is thermally stable at a temperature of at least 200°C.

Preferably the ester is an organic acid ester having one or more monobasic acid groups wherein said organic acid is most preferably a sulfonic acid or an α-substituted carboxylic acid, particularly a haloacetic acid.

The invention also relates to foundry binder systems where (a) and (b) are separate components. Foundry mixes are prepared by mixing the binder components with a foundry aggregate. The invention also relates to a method of preparing a foundry shape, the shapes prepared, a method of making a metal casting, and metal castings prepared by this process.

The ester used in the binder compositions is such that the binder has all of the following advantages:

1. The binder composition is a stable and homogeneous solution at use conditions, even at temperatures as low as -20°C

The binder composition produces foundry shapes that readily shakeout from castings made with the foundry shapes, particularly when the castings are made with aluminum.

The binders produce foundry shapes with adequate tensile strengths needed for use in casting metal parts. 4. The binder curing efficiency of the binder composition is better than that provided by similar compounds, which results in the use of lower amine catalyst.

5. The binder is non corrosive.

In view of these preferred attributes, sulfonates and haloacetates are particularly preferred as the ester additive. Particularly useful as the binder for the amine curable binder composition are phenolic-urethane binders and epoxy-acrylic-isocyanate binders.

BEST MODE AND OTHER EMBODIMENTS OF THE INVENTION

Examples of amine curable foundry binders that are used in this invention include phenolic-urethane binders and epoxy-acrylic-isocyanate binders. For purposes of describing this invention, a foundry shape is any shape made from a foundry aggregate and organic binder that is used in a molding assembly for casting metal parts. A casting assembly is an arrangement of foundry shapes in a pattern such that a metal casting will be produced when molten metal is poured into the casting assembly and allowed to cool. An internal core is a core that is imbedded in the casting assembly. A foundry mix is a mixture of a foundry binder, and aggregate, and possibly a curing catalyst. Phenolic-urethane binders are well known. Preferably, the phenolic-urethane binder is an ISOCURE® cold-box phenolic-urethane binder cured by passing a tertiary amine gas, such a triethylamine, through the molded sleeve mix in the manner as described in U.S. Patent 3,409,579 and 3,676,392, which are incorporated by reference. Typical gassing times are from 0.5 to 3.0 seconds, preferably from 0.5 to 2.0 seconds. Purge times are from 1.0 to 60 seconds, preferably from 1.0 to 10 seconds.

Another preferred amine curable cold-box binder is an epoxy-acrylic- polyisocyanate binder, such as compositions shown in U.S. Patent 5,880,175, which is hereby incorporated by reference. This patent discloses a binder that incorporates aspects of U.S. Patent 3,409,579 and U.S. Patent 4,526,219. Although the binder is amine curable, it also undergoes a free radical cure, but for purposes of this invention is considered amine curable.

Any ester may be used that is derived from an organic acid having a pK_a< 3.0, preferably <1.0., and most preferably <0.8 that is thermally stable at >200°C, preferably at >300°C. Preferably, the ester is an ester of a monobasic organic acid where the ester has one or more monobasic acid groups. The most preferably used esters are sulfonate esters and haloacetate esters.

The pK_a of the acid used to form the ester is defined as -log(K_a), where K_a is the ionization constant of an acid in aqueous solution and is determined by a variety of methods, including conductance, electrometric, catalytic, and spectroscopic (for summary and references, see Dissociation of Acids in Aqueous Solution by G. Kortum, W. Vogel, and K. Andrussow, Butterworths, London, 1961, pp. 194-229). Thermal stability is determined by observing a change in some property of the acid, e.g. weight loss, infrared spectrum etc. while holding it at some desired temperature for a given length of time, e.g. 200°C for 15 minutes.

Examples of sulfonate esters include monofunctional esters, multifunctional esters (busulfan), and cyclic esters (sultones) , and mixtures thereof. Examples of sultones include 1,3-propanesultone, and 1,4-butanesultone . Preferably used as the sulfonate esters are compounds represented by the following structure:

O II R1— S-O

where Ri and R₂ are individually aliphatic groups containing 1-20 carbons. Other substituents may be attached to Rl and R2, such as other aliphatic and aromatic residues, halogens, NO₂, carboxy esters, sulfonate esters, ethers, ketones, aldehydes, and the like. The Rl and R2 groups may be linked together to form rings of cyclic sulfonate esters known as sultones. Examples of preferably used sulfonates are methyl .-toluenesulfonate, ethyl -toluenesulfonate, butyl p-toluenesulfonate, and 1,4- butanesultone. α-Substituted carboxylate esters used in the binder are represented by the following structure:

where X is an electron withdrawing group such as a halogen atom, e.g. fluorine, chlorine, bromine or iodine, nitro, sulfonyl, etc., n is an integer of value 1-3, Rl is a hydrogen or an aryl or an aliphatic or a mixed aryl aliphatic group containing from 1- 20 carbons, and R2 is an aryl or aliphatic, or mixed aryl aliphatic groups containing from 1-20 carbons. Other substituents may be attached to the R groups, such as other aliphatic and aromatic groups, NO₂, carboxy esters, sulfonate esters, ethers, ketones, aldehydes, and the like. Preferably used as the substituted carboxylate esters are haloacetate esters, particularly t-butyl chloroacetate, ethyl trichloroacetate, and phenyl trifluoroacetate. The ester is added to the foundry aggregate and/or to one or more of the reactive or non reactive components of the organic binder in which it is compatible. Preferably, the ester is added to the isocyanate-containing component of the binder. As was mentioned before, foundry shapes are preferably made with the binder by the cold- box process, which involves blowing or ramming the foundry mix into a pattern where it is shaped, and then curing the foundry shape with a vaporous or gaseous amine catalyst. Preferably the cold-box binder is an ISOCURE® phenolic-urethane binder or an ISOMAX™ binder cured by passing a tertiary amine gas, such as triethylamine, through the molded foundry shape in the manner as described in U.S. Patents 3,409,579 and 3,676,392, which are hereby incorporated into this disclosure by reference. Typical gassing times are from 0.5 to 20.0 seconds, preferably from 0.5 to 6.0 seconds. Purge times are from 1.0 to 60 seconds, preferably from 1.0 to 20 seconds.

The amount of ester needed in the binder is an amount that is effective to facilitate the removal of the sand, used to form the foundry shape, from the metal casting formed with the foundry shape. This amount is typically from 0.5to 15.0 weight percent based on the weight of the binder, preferably from 1.0 to 10.0 weight percent; most preferably from 2.0 to 5.0 weight percent. Various types of aggregate and amounts of binder are used to prepare foundry mixes by methods well known in the art. 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. The amount of binder needed is an amount that is effective in producing a foundry shape that can be handled or is self-supporting after curing. In ordinary sand type foundry applications, the amount of binder is generally no greater than about 10% by weight and frequently within the range of about 0.5% to about 7% by weight based upon the weight of the aggregate. Most often, the binder content for ordinary sand foundry shapes ranges from about 0.6% to about 5% by weight based upon the weight of the aggregate in ordinary sand-type foundry shapes.

Optional ingredients for the binder include release agents, benchlife extenders, and adhesion promoters to improve humidity resistance, e.g. silanes as described in U.S. Patent

4,540,724 which is hereby incorporated by reference.

A description of the components used in the examples follows:

ISOCURE® binder = a two-part polyurethane-forming cold-box binder. The

Part I is the phenolic resin component, which is a blend of a phenolic resole benzylic ether (PRBE) resin having a

GPC weight average molecular weight of from about 800 to 1200, prepared by reacting phenol and formaldehyde along the lines of the process described in U.S. Patent 3,485,797; and a solvent blend consisting primarily of aromatic solvents and ester solvents. The Part II is the polyisocyanate component, which comprises a polymethylene polyphenyl isocyanate (PMPI), a solvent blend consisting primarily of aromatic solvents and a minor amount of aliphatic solvents, and a benchlife extender. The weight ratio of Part I to Part II is about 55:45. Unless otherwise stated in the examples, the ISOCURE® binder formulation used was as follows: Part i

Constituent Weiεht %

PRBE Resin 53.0

Dibasic Ester 16.9

Aromatic Solvent 28.6

Tall Oil Fatty Acid 1.0

Epoxy-Functional Silane 0.5

Part II

Constituent Weight %

PMPI 71.0

Aromatic Solvent 24.5

Polymerized Linseed Oil 4.0

Monophenyl Dichlorophosphate 0.5

ISOSET® binder an epoxy-acrylic binder containing an oxidizing agent that is cured by a free radical process in the presence of sulfur dioxide, according to the general procedures disclosed in U.S. Patent 4,518,723.

ISOMAX™ binder = a two-part acrylic/coreactant/polyisocyanate cold-box binder prepared along the lines shown in U.S. Patent 5,880,175. The Part I is the coreactant component, which consists of an epoxy resin, a hydroperoxide as part of the curing agent system, and a solvent blend consisting primarily of aromatic solvents and aliphatic solvents. The Part II is the acrylic/polyisocyanate component, which comprises an acrylic acid or methacrylic acid ester monomer, a polymethylene polyphenyl isocyanate, and a solvent blend consisting primarily of aromatic solvents and aliphatic solvents. The weight ratio of Part I to Part II is about 20:80. ETSA ethyl p-toluenesulfonate.

BISULFAN = bisulfan.

BCA t-butyl chloroacetate.

BTSA butyl p-toluenesulfonate.

ETCA ethyl trichloroacetate.

BTST 1 ,4-butanesultone.

TSA p-toluenesulfonic acid.

TSA-Na sodium p-toluenesulfonate.

MESA methyl p-toluenesulfonate

EXAMPLES

The following examples illustrate the application of the present invention. Controls were run without any ester additive and are designated as "Control" followed by an "X" or "Y" or multiple "X"s or multiple "Y"s for the experiments using ISOCURE® binders, "Z" or multiple "Z"s for the experiments using ISOMAX™ binders, and "W" for the experiment using ISOSET® binder. The comparative examples used TSA and TSA-Na. They are designated by the letters "A" or "B" and multiple thereof for experiments using ISOCURE® binders, and the letter "C" for the experiment using ISOSET® binder. Table I discloses the acids used to form the esters used in the examples, the pK_a of the acid. All of the acids have degradation temperatures greater than 200°C.

TABLE I STRONG ACIDS OF ESTERS USED IN BINDERS

EXAMPLES USING AN ISOCURE® BINDER

Foundry mixes were made by mixing amine curable ISOCURE® cold-box foundry binder and an ester on Wedron 540 silica sand. The amount of binder used was 0.90% based on the weight of sand used. The amount of ester used was 0.0023 ester mole-equivalents per 1000 g. of sand used. The sand mix compositions are described in Table II. TABLE II ISOCURE® BINDER SAND MIX COMPOSITIONS

Test cores were made by blowing the foundry mix into a pattern corebox. The shaped mix in the corebox was contacted with triethyl amine (TEA) at 20 psi for 0.5 second, followed by a 6 second air purge at 60 psi. Before testing, the test cores were stored in a constant temperature (CT) room that was maintained at a temperature of 25°C and a relative humidity of 50%. The tensile strengths of the cores made with the binder and the shakeout of foundry cores from castings were measured to determine the effect of including the ester in the binder-sand mix.

For measuring tensile strength, AFS tensile strength test cores in the shape of dogbones were produced. The tensile strength data are summarized in Table III that follows.

TABLE III

TENSILE STRENGTHS OF TEST CORES MADE WITH ISOCURE®

BINDERS

For measuring shakeout performance, test cores were produced that were solid and shaped like a trapezoid (tree-shaped) and had a height of 1". There are two 5" converging sides to the trapezoid. The converging sides of the trapezoid create two end "faces", one having a length of 1.50", and the other having a length of 3.75". The trapezoid test cores had three tubular stems, one on the 1.5" face and two on the 3.75" face. The stems in the trapezoid test cores were designed so that holes result in the aluminum casting made from the trapezoid test core. The hole-generating stems were 0.75" in diameter.

The test cores were used as internal cores to make an aluminum casting. A test core was placed in the bottom half of a sand mold designed for placement of the test core. Then the top half of the mold, which contained a sprue through which metal could be poured, was inserted on top of the bottom half.

Molten Aluminum 319 having a temperature of 730° C was poured into the casting assembly and then allowed to cool. The resulting aluminum casting was a hollow trapezoid having a thickness of 0.25". There is one hole at the center of the 1.5" end face of the trapezoid and two holes on the 3.75" end face that are about 1.5" apart and each about 0.75" from the end. The top of the trapezoid casting had a block of metal protruding from it that is used to attach the aluminum casting to the Herschal hammer used during the shakeout test.

'Although the sand mixes from Examples 2, 3 and 4 were not tested for tensile strength, the additives used are expected to behave similarly to other esters of this invention, i.e. they are not likely to have any significant positive or negative influence on core tensile strengths when tested in other ISOCURE® binder formulations. The shakeout tests where conducted on castings cooled to room temperature (cold) by attaching the aluminum casting to a mechanical Herschal hammer to the protrusion on the trapezoid test casting. The Herschal hammer pressure was set to 40 psi and was used to shake the casting for 15 second intervals until the internal core was removed from the aluminum casting through the single hole in the 1.5 inch face of the trapezoid test casting. The amount of sand exiting the casting from the hole on the 1.5 inch face of the trapezoid casting was measured every 15 seconds. The data are summarized in Table IV below. It is seen that the esters and TSA were the most effective in increasing shakeout speed. Cores prepared with the binder containing the TSA-Na had the least improved shakeout over the control. However, because of the corrosive nature of TSA, the lower binder solubility of TSA, and its adverse effect on curing efficiency, it is not desirable for use in the coremaking process.

TABLE IV

COLD SHAKEOUT TEST RESULTS OF CORES MADE

WITH ISOCURE® BINDERS

TABLE V BULK CURE TESTS FOR ISOCURE® BINDERS

The bulk cure test is a method used for determining the curing efficiency of a binder with a given amine or for comparing the curing efficiency of various amines relative to a given resin system. The procedure includes preparing the foundry mix with the sand and binder, loading the foundry mix into a cylindrical chamber, and gassing with a fixed amount of the catalyst (triethylamine). Bulk cure studies were performed with a known amount of catalyst (100 microliters of triethylamine heated to 66°C), known amount of binder level (0.90 wt%), and in 1200 grams of sand with a 55:45 ratio of Part I to Part II. The curing efficiency is calculated on the basis of the proportion by weight of the sand mix cured, or hardened, for the particular binder. The procedure involves the use of a cold box binder system.

Table V shows that the binder that contained ETSA resulted in increased curing efficiency (bulk cure) when compared to the curing efficiency of the control and comparative examples. Curing efficiency of the binder containing the TSA is particularly inefficient. An increase in curing efficiency means that less catalyst is used, which reduces costs and stress to the environment.

TABLE V CURING EFFICIENCY OF ISOCURE® BINDERS

In the following examples, other sulfonate esters were tested in a different ISOCURE® binder formulation (ISOCURE® 389F/689F) for effects on core tensile strengths and shakeout speed. The foundry sand mixes were prepared as in the previous examples, except that the sulfonate esters were added to either the phenolic resin component (Part I) or the polyisocyanate component (Part II). The amount of sulfonate ester incorporated was 5% based on the total weight of the binder. The sand mix compositions are described in Table II.

TABLE VI ISOCURE® BINDER SAND MIX COMPOSITIONS

The tensile strengths of the cores made with the binder and the shakeout of foundry cores from castings were measured to determine the effect of including the ester in the binder-sand mix.

The tensile strength data are summarized in Table VII that follows.

TABLE VII TENSILE STRENGTHS OF TEST CORES MADE WITH ISOCURE®

BINDERS

The shakeout tests where conducted on castings immediately after removing them from the casting molds which was 25 minutes after pouring the molten Aluminum319. At this point, the temperature of the castings was about 275°C (hot). These conditions simulate those found in some foundry operations. The shakeout data are summarized in Table VIII below. TABLE VIII HOT SHAKEOUT TEST RESULTS OF CORES MADE WITH ISOCURE®

BINDERS

A review of the data in Tables I through VIII shows that only the sulfonate esters and haloacetates provide all the advantages desired in for the cold-box process, i.e. a binder that produces foundry shapes that readily shakeout from castings made with the foundry shapes; a binder that produces foundry shapes with more than adequate tensile strengths needed for use in casting metal parts; a binder with improved curing efficiency; and a binder that is noncorrosive.

EXAMPLES USING ISOMAX™ BINDER

Similar tests to those conducted with the ISOCURE® binder were conducted with an ISOMAX™ binder. The binder compositions were formed by mixing 3.0 weight per cent ester, based on the weight of the total binder, with the acrylic/isocyanate component (Part II) of the ISOMAX™ binder.

Foundry sand mixes were made by mixing 1.20 weight percent of amine- curable ISOMAX™ cold-box foundry binder containing ester additive with Wedron 540 sand, where the weight of the binder is based upon the amount of Wedron sand used. The binder sand mix compositions are described in Table IX.

TABLE IX ISOMAX™ BINDER SAND MIX COMPOSITIONS

Test cores were made by blowing the foundry mix into a pattern corebox. The shaped mix in the corebox was contacted with triethyl amine (TEA) at 20 psi for 1.0 second, followed by a 20 second nitrogen purge at 20 psi. Before testing, the test cores were stored in a constant temperature (CT) room that was maintained at a temperature of 25°C and a relative humidity of 50%. The tensile strengths of the cores made with the binder and the shakeout of foundry cores from castings were measured, as in previous examples, to determine the effect of including the ester in the binder-sand mix. The tensile strength data are summarized in Table X that follows. TABLE X

TENSILE STRENGTHS OF TEST CORES MADE WITH ISOMAX™

BINDERS

Hot shakeout tests were conducted, as described in previous examples, with the ISOMAX™ binder mix compositions. The shakeout data are summarized in Table XI below.

TABLE XI HOT SHAKEOUT TEST RESULTS OF CORES MADE WITH ISOMAX™ BINDERS

A review of the data in Tables IX through XI shows that the sulfonate esters provide all the advantages desired in for the cold-box process using an ISOMAX™ binder: a binder that produces foundry shapes that readily shakeout from castings made with the foundry shapes; a binder that produces foundry shapes with more than adequate tensile strengths needed for use in casting metal parts; and a binder that is noncorrosive.

COMPARISON EXAMPLE USING AN ISOSET® BINDER Similar shakeout tests to those conducted with the ISOCURE® and ISOMAX™ binders were conducted with another well known cold-box binder known as ISOSET® binder. This cold-box binder is epoxy-acrylate binder that is cured with sulfur dioxide (SO₂). The Part I consisted of a mixture of an epoxy resin and cumene hydroperoxide, and the Part II consisted of a mixture of a multifunctional acrylate ester and high boiling aliphatic and ester solvents. In these tests, a Part I/Part II weight ratio of 60/40 was used. The binder composition was formed by mixing 3.0 weight per cent BTSA ester, based on the weight of the total binder, with the Part II of the ISOSET® binder. A foundry mix was made by mixing 0.90 weight percent of SO₂-curable ISOSET® cold-box foundry binder containing BTSA ester additive with Badger 5574 sand, where the weight of the binder is based upon the amount of Badger sand used.

Shakeout test cores were made by blowing the foundry mix into a pattern corebox to make internal test cores that were used in casting an aluminum part. The shaped mix in the corebox was contacted with 100% SO₂ at 30 psi for 1.0 second, followed by a 10 second air purge at 30 psi. The test cores were stored in a CT room, until they were ready to be tested.

The shakeout tests where conducted on castings immediately after removing them from the casting molds which was 25 minutes after pouring the molten Aluminum319. At this point, the temperature of the castings was about 275°C (hot). The data from the hot shakeout tests are summarized in Table XII below.

TABLE XII HOT SHAKEOUT TEST RESULTS OF CORES MADE WITH ISOSET®

BINDERS

The results of these tests showed that the addition of the sulfonate ester, BTSA, did not improve shakeout of the cores from castings made with the ISOSET® cold-box binder.

Claims

CLAIMSWe claim:

1. An amine curable foundry binder composition comprising as a mixture:

(a) an amine curable organic foundry binder selected from the group consisting of phenolic-urethane and epoxy-acrylic-isocyanate binders; and

(b) an ester of an organic acid in an amount effective to facilitate removal of a foundry shape from a metal casting, wherein said acid:

(i) has a pKa of less than 3.0, preferably less than 1.0, and more preferably less than 0.8; and

(ii) is thermally stable at a temperature of at least 200°C.

2. The foundry binder composition of claim 1 wherein the ester is an ester of an organic acid having one or more monobasic acid groups.

3. The foundry binder composition of claim 2 wherein the ester is selected from the group consisting of sulfonate esters, substituted carboxylate esters, and mixtures thereof.

4. The foundry binder of claim 3 wherein the ester is a sulfonate ester selected from the group consisting of methyl p-toluenesulfonate, ethyl p- toluenesulfonate, butyl p-toluenesulfonate, 1,4-butanesultone, and mixtures thereof.

5. The foundry binder composition of claim 3 wherein the carboxylate ester is an α-halocarboxylate.

6. The foundry binder of claim 5 wherein the α-halocarboxylate is selected from the group consisting of t-butyl chloroacetate, ethyl trichloroacetate, phenyl trifluoroacetate, and mixtures thereof.

7. A foundry mix comprising:

(a) a major amount of a foundry aggregate;

(b) a minor amount of the binder composition of claim 1, 2, 3, 4, 5, or 6.

8. A cold-box process for preparing foundry shapes which comprises:

(A) introducing a foundry mix of claim 7 into a pattern to prepare an uncured foundry shape;

(B) contacting said uncured foundry shape prepared by (A) with a vaporous amine curing catalyst;

(C) allowing said foundry shape resulting from (B) to cure until said shape becomes handleable; and

(D) removing said foundry shape from the pattern.

9. A foundry shape prepared in accordance with claim 8.

10. A process for casting a metal part which comprises:

(A) inserting a foundry shape of claim 9 into a casting assembly;

(B) pouring metal, while in the liquid state, into said casting assembly;

(C) allowing said metal to cool and solidify; and (D) then separating the cast metal part from the casting assembly.

11. The process of claim 10 wherein the metal is aluminum.

12. A metal part prepared in accordance with claim 11.

13. An amine curable cold-box foundry binder system comprising as separate components:

(A) a phenolic resole resin component;

(B) a polyisocyanate component; and

(C) an ester of an organic acid wherein said acid

(1) has a pKa of less than 3.0, preferably less than 1.0, and more preferably less than 0.8; and

(2) is thermally stable at a temperature of at least 200°C,

where said ester is included in component (A), (B), or both.

14. The binder system of claim 13 wherein the ester is an ester of an organic acid having one or more monobasic acid groups.

15. The binder system of claim 14 wherein the ester is selected from the group consisting of sulfonate esters, substituted carboxylate esters, and mixtures thereof.

16. The binder system of claim 15 wherein the ester is a sulfonate ester selected from the group consisting of methyl p-toluenesulfonate, ethyl p- toluenesulfonate, butyl p-toluenesulfonate, 1,4-butanesultone, and mixtures thereof.

17. The binder system of claim 16 wherein the carboxylate ester is an α- halocarboxylate.

18. The binder system of claim 17 wherein the α-halocarboxylate is selected from the group consisting of t-butyl chloroacetate, ethyl trichloroacetate, phenyl trifluoroacetate, and mixtures thereof.

19. An amine curable cold-foundry binder system comprising as separate components:

(A) from 0 to 75 weight percent of an epoxy resin;

(B) from 5 to 80 weight percent of an organic polyisocyanate;

(C) from 5 to 75 weight percent of a reactive unsaturated acrylic monomer or polymer; and

(D) an effective amount of an oxidizing agent,

(E) an ester of an organic acid wherein said acid

(1) has a pK_a of less than 3.0, preferably less than 1.0, and more preferably less than 0.8; and

(2) is thermally stable at a temperature of at least 200°C,

where (A), (B), (C), (D), and (E) are separate components or mixed with another of said components, provided (B) or (C) is not mixed with (D), and where said weight percents are based upon the total weight of (A), (B), (C), (D), and (E).

20. The binder system of claim 19 wherein the ester is an ester of an organic acid having one or more monobasic acid groups.

21. The binder system of claim 20 wherein the ester is selected from the group consisting of sulfonate esters, substituted carboxylate esters, and mixtures thereof.

22. The binder system of claim 21 wherein the ester is a sulfonate ester selected from the group consisting of methyl p-toluenesulfonate, ethyl p- toluenesulfonate, butyl p-toluenesulfonate, 1,4-butanesultone, and mixtures thereof.

23. The binder system of claim 22 wherein the carboxylate ester is an α- halocarboxylate.

24. The binder system of claim 23 wherein the α-halocarboxylate is selected from the group consisting of t-butyl chloroacetate, ethyl trichloroacetate, phenyl trifluoroacetate, and mixtures thereof.