WO2002060985A1

WO2002060985A1 - Phenolic urethane foundry binders containing methyl benzoate

Info

Publication number: WO2002060985A1
Application number: PCT/US2001/003191
Authority: WO
Inventors: Raja Iyer
Original assignee: Borden Chemical, Inc.
Priority date: 2001-01-31
Filing date: 2001-01-31
Publication date: 2002-08-08

Abstract

An embodiment of the present invention provides a method for improving the tensile strength of foundry cores and molds bound using a phenolic urethane binder. A further embodiment of the present invention provides a method for improving humidity resistance, cure time and the anti-warp characteristics of foundry cores and molds using a phenolic urethane binder. More particularly, an embodiment of the present invention provides an improved phenolic urethane binder for foundry cores and molds that include methyl benzoate. In a preferred embodiment, a modified part 1 phenolic urethane binder component includes the user of methyl benzoate with a phenolic resin.

Description

PHENOLIC URETHANE FOUNDRY BINDERS CONTAINING METHYL

BENZOATE

Field of the Invention

This invention relates to an improved urethane binder system for foundry cores and ' molds. The invention further relates to the use of methyl benzoate in a urethane foundry binder. The present invention also relates to a method for improving the humidity resistance, tensile strength and anti-warp characteristics of a urethane binder system and the foundry cores or molds made using such a system.

Background of the Invention

Binders or binder systems for foundry cores and molds are well known. In the foundry art, cores or molds for making metal castings are normally prepared from a mixture of an aggregate material, such as sand, and a binding amount of a binder system. Typically, after the aggregate material and binder have been mixed, the resultant mixture is rammed, blown or otherwise formed to the desired shape or patterns, and then cured with the use of catalyst and/or heat to a solid, cured state.

Resin binders used in the production of foundry molds and cores are often cured at high temperatures to achieve the fast-curing cycles required in foundries. However, resin binders have been developed which cure at a low temperature, to avoid the need for high- temperature curing operations which have higher energy requirements and which often result in the production of undesirable fumes.

One group of processes which do not require heating in order to achieve curing of the resin binder are referred to as 'cold-box' processes. In such processes, the binder components are coated on the aggregate material, such as sand, and the material is blown into a box of the desired shape. Curing of the binder is carried out by passing a gaseous catalyst at ambient temperatures through the molded resin-coated material. Where such processes use urethane binders, the binder components comprise a polyhydroxy component and a polyisocyanate component. These cure to form a polyurethane in the presence of a gaseous amine catalyst. Another group of binder systems which do not require gassing or heating in order to bring out curing are known as 'no-bake' systems. No-bake systems based on the use of urethane binders and an aggregate material, such as sand, coated with a polyhydroxy component and a polyisocyanate component. In this case, a liquid tertiary amine catalyst is combined with the polyhydroxy component at the time of mixing and the mixed aggregate and binder is allowed to cure in a pattern or core box at ambient or slightly higher temperatures.

As alluded to above, the binder for the urethane cold-box or no-bake systems is a two- part composition. Part one of the binder is a polyol (comprising preferably hydroxyl containing phenol formaldehyde resin) and part two is an isocyanate (comprising preferably polyaryl polyisocyanates). Both parts are in a liquid form and are generally used in combination with organic solvents. To form the binder and thus the foundry sand mixture, the polyol part and the isocyanate part are combined. After a uniform mixture of the foundry sand and parts one and two is achieved, the foundry mix is formed or shaped as desired. Parts one and/or two may contain additional components such as, for example, mold release agents, plasticizers, inhibitors, etc.

Liquid amine catalysts and metallic catalysts, known in the urethane technology, are employed in a no-bake composition. The catalyst may be incorporated into either part one or two of the system or it may be added after uniform mixing as a part three. By selection of a proper catalyst, conditions of the core making process, for example, worktime (assembling and admixing components and charging the admixture to a mold) and strip time (removing the molded core from the mold) can be adjusted.

In cold-box technology, the curing step is accomplished by suspending a tertiary amine catalyst in an inert gas stream and passing the gas stream containing the tertiary amine, under sufficient pressure to penetrate the molded shape until the resin is cured.

Improvements in resinous binder systems which can be processed according to the cold-box or no-bake process generally arise by modifying the resin components, i.e., either the polyol part or the isocyanate part. For instance, U.S. Pat. No. 4,546,124, which is incorporated herein by reference, describes an alkoxy modified phenolic resin as the polyhydroxy component. The modified phenolic resin improves the hot strength of the binder systems. U.S. Pat. No. 5,189,079, which is herein incorporated by reference, discloses the use of a modified resole resin. These resins are desired because they emit reduced amounts of formaldehyde. U.S. Pat. No. 4,293,480, herein incorporated by reference, relates to improvements in the isocyanate component which enhances shake-out properties of non- ferrous castings.

While a number of improvements in urethane binder systems have been described, a need exists for urethane binder systems that are not only more cost effective, but show improved mechanical qualities. Those qualities include improvements in tensile strength, humidity resistance and a decrease in the warp or sag of the urethane bonded cores and molds.

Summary of the Invention

The present invention relates to improving the binder system by using methyl benzoate as an addition to, or substitute for, the polar solvents in the part one component of the aforementioned phenolic urethane binder. The addition of methyl benzoate in this invention has shown surprising and unexpected improvements in the tensile strength, humidity resistance and anti-warp characteristics of urethane binder systems. Furthermore, the use of methyl benzoate in these urethane binders has proven to be a low cost method for improving these binders.

The advantages realized with embodiments of the present invention include a surprising increase in tensile strength, humidity resistance and a dramatic increase in anti- warp characteristics. One additional advantage is the sharp reduction in manufacturing costs achievable with the binder systems made in accordance with the principles of the present invention.

Other aspects and advantages of the present invention will become apparent from the following Detailed Description and the examples.

Detailed Description of the Invention

According to one embodiment of the present invention, there is provided a composition that results in an increased humidity resistance, tensile strength and anti-warp characteristics of foundry cores and molds as compared to the prior art. It has been discovered that methyl benzoate when used in a phenolic urethane binder, in amounts ranging from about 1% to about 25%, or more, and preferably from about 3% to about 15%, based on the total weight of part one binder component, provides shaped articles, surprisingly and unexpectedly, exhibiting improved mechanical properties including an increase in strength. It has further been discovered that the use of methyl benzoate in a phenolic urethane binder system also provides faster cure speeds and improved anti-warp characteristics.

The methyl benzoate that is useful in embodiments of the present invention is preferably a by-product stream. As used herein, methyl benzoate means all the varying degrees of purity of methyl benzoate. Such by-product streams provide a low-cost methyl benzoate, which can result in a reduction of the overall cost of the phenolic urethane binder system. Methyl benzoate useful in embodiments of the present invention may be purchased from KOSA, Wilmington, North Carolina. This methyl benzoate contains about 98.3% pure methyl benzoate, about 0.2% p-tolualdehyde and about 0.2% water. The composition of one embodiment of the present invention is useful as a phenolic urethane foundry binder. Such a phenolic urethane foundry Binder will bind together aggregate material, typically sand, in a pre-formed shape. The phenolic urethane foundry binder includes a part one component and a part two component, as described above, which are cured using a suitable catalyst. A foundry core or mold is typically prepared by mixing sand with a part one binder component, a part two binder component, and applying either a liquid or vaporous catalyst. The part one binder component and the part two binder component in combination form a binder. In the no-bake process, referred to above, the part one binder component, part two binder component and a liquid catalyst are mixed with a foundry aggregate. This mixture is then discharged into a pattern and cured. Similarly, in the cold-box process a foundry core or mold is prepared by mixing sand with a part one binder component and a part two binder component, discharging the mixture into a pattern, and curing the mixture by passing a vaporous catalyst through the mixture of sand and resin.

In one embodiment of the present invention, a part one binder component is modified by combining a resole resin with methyl benzoate and other components. However, it will be recognized by those of ordinary skill in the art that other means of introducing the methyl benzoate to the phenolic urethane foundry binder may be employed. Such other means include adding the methyl benzoate to the part two binder component, or providing the methyl benzoate as a third component, which may be added to the phenolic urethane foundry binder at about the time the part one binder component and the part two binder component are mixed with an aggregate.

Use of Methyl Benzoate In A Urethane Binder System

As noted above, it has been discovered that methyl benzoate when used in a phenolic urethane binder provides shaped articles exhibiting unexpected improved mechanical properties including improved strength. It has been further discovered that the benefits may be realized using combinations of methyl benzoate and a variety of polar solvents. Additionally, other compounds may be used with the combination of methyl benzoate and polar solvents to enhance the benefits otherwise realized with the combination.

Part One Binder Component The part one binder component is preferably a phenolic resin in a solution of organic solvents and/or plasticizers. In the compositions of the present invention resoles, novolacs, and combinations of these phenolic resins may be used. One preferred cold-box part one binder component useful in embodiments of the present invention is SIGMA CURE 7121, made and sold by Borden Chemical, Inc., Louisville, Kentucky. This binder component has a viscosity of about 300 cps, a solids content of about 57%, free phenol content of about 5%, and a free formaldehyde of less than 0.1%. A preferred no-bake part one binder component useful in embodiments of the present invention is SIGMA SET 6000, made and sold by Borden Chemical, Inc., Louisville, Kentucky. This binder component has a viscosity of about 110 cps, a solids content of about 57%, free phenol content of about 5%, and a free formaldehyde of less than 0.1%. Phenolic Resole Resins

Resole resins are thermosetting, i.e., they form an infusible three-dimensional polymer upon application of heat and are produced by the reaction of a phenol and a molar excess of a phenol-reactive aldehyde typically in the presence of an alkali, alkaline earth, or other metal compound as a condensing catalyst. The phenolic resole which may be used with the embodiments of the present invention may be obtained by the reaction of a phenol, such as phenol itself, cresol, resorcinol, 3,5-xylenol, bisphenol-A, other substituted phenols, and mixtures of any of these compounds, with an aldehyde such as, for example, formaldehyde, paraformaldehyde, acetaldehyde, furfuraldehyde, and mixtures of any of these aldehydes. A broad range of phenolic resoles in fact may be used with the various embodiments of this invention. These can be phenol-formaldehyde resoles or those where phenol is partially or completely substituted by one or more reactive phenolic compounds and the aldehyde portion can be partially or wholly replaced by other aldehyde compounds. The preferred phenolic resole resin is the condensation product of phenol and formaldehyde. Any of the conventional phenolic resole resins or alkoxy modified resole resins may be employed as the phenolic resin with the present invention. Of the alkoxy modified resole resins, methoxy modified resole resins are preferred. However, the phenolic resole resin which is most preferred is the modified orthobenzylic ether-containing resole resin prepared by the reaction of a phenol and an aldehyde in the presence of an aliphatic hydroxy compound containing two or more hydroxy groups per molecule. In one preferred modification of the process, the reaction is also carried out in the presence of a monohydric alcohol. Phenols suitable for preparing the modified orthobenzylic ether-containing phenolic resole resins are generally any of the phenols which may be utilized in the formation of phenolic resins, and include substituted phenols as well as unsubstituted phenol per se. The nature of the substituent can vary widely, and exemplary substituted phenols include alkyl- substituted phenols, aryl-substituted phenols, cycloakyl-substituted phenols, alkenyl- substituted phenols, alkoxy-substituted phenols, aryloxy-substituted phenols and halogen- substituted phenols. Specific suitable exemplary phenols include in addition to phenol per se, o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 3,4,5-trimethyl phenol, 3-ethyl phenol, 3,5-diethyl phenol, p-butyl phenol, 3,5-dibutyl phenol, p-amyl phenol, p-cyclohexyl phenol, p-octyl phenol, 3,5-dicyclohexyl phenol, p-phenyl phenol, p-crotyl phenol, 3,5-dimethoxy phenol, 3,4,5-trimethoxy phenol, p-ethoxy phenol, p-butoxy phenol, 3-mefhyl-4-methoxy phenol, and p-phenoxy phenol. A preferred phenolic compound is phenol itself.

The aldehyde employed in the formation of the modified phenolic resole resins can also vary widely. Suitable aldehydes include any of the aldehydes previously employed in the formation of phenolic resins, such as formaldehyde, acetaldehyde, propionaldehyde and benzaldehyde. In general, the aldehydes employed contain from 1 to 8 carbon atoms. The most preferred aldehyde is an aqueous solution of formaldehyde.

Metal ion catalysts useful in production of the modified phenolic resins include salts of the divalent ions of Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca and Ba. Tetra alkoxy titanium compounds of the formula Ti(OR) where R is an alkyl group containing from 3 to 8 carbon atoms, are also useful catalysts for this reaction. A preferred catalyst is zinc acetate. These catalysts give phenolic resole resins wherein the preponderance of the bridges joining the phenolic nuclei are ortho-benzylic ether bridges.

A molar excess of aldehyde per mole of phenol is used to make the modified resole resins. Preferably the molar ratio of phenol to aldehyde is in the range of from about 1 : 1.1 to about 1 :2.2. In a preferred embodiment, the phenol and aldehyde are reacted in the presence of the divalent metal ion catalyst at pH below about 7. A convenient way to carry out the reaction is by heating the mixture under reflux conditions. Reflux, however, is not required. In one embodiment, an aliphatic hydroxy compound which contains two or more hydroxy groups per molecule is added to the reaction mixture. The hydroxy compound is added at a molar ratio of hydroxy compound to phenol of from about 0.001:1 to about 0.03:1. This hydroxy compound may be added to the phenol and aldehyde reaction mixture at any time when from 0% (i.e., at the start of the reaction) to when about 85% of the aldehyde has reacted. It is preferred to add the hydroxy compound to the reaction mixture when from about 50% to about 80% of the aldehyde has reacted. Useful hydroxy compounds which contain two or more hydroxy groups per molecule are those having a hydroxyl number of from about 200 to about 1850. Suitable hydroxy compounds include ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, triethylene glycol, glycerol, sorbitol and polyether polyols having hydroxyl numbers greater than about 200. Glycerol is a particularly suitable hydroxy compound.

The reaction mixture, is typically heated until from about 80% to about 98% of the aldehyde has reacted. Although the reaction can be carried out under reflux until about 98% of the aldehyde has reacted, prolonged heating is required and it is preferred to continue the heating only until about 80% to 90%) of the aldehyde has reacted. At this point, the reaction mixture is heated under vacuum at a pressure of about 50 mm of Hg until the free formaldehyde in the mixture is less than about 1%. Preferably, the reaction is carried out at 95° C until the free formaldehyde is less than about 0.1% by weight of the mixture. The catalyst may be precipitated from the reaction mixture before the vacuum heating step if desired. Citric acid may be used for this purpose. The modified phenolic resole may be "capped" to be an alkoxy modified phenolic resole resin. In capping, a hydroxy group is converted to an alkoxy group by conventional methods that would be apparent to one skilled in the art given the teachings of the present disclosure.

Novolac Resins Novolac resins are obtained by the reaction of a phenol and an aldehyde in a strongly acidic pH region. Suitable catalysts include the strong mineral acids such as sulfuric acid, phosphoric acid and hydrochloric acid as well as organic acid catalysts such as oxalic acid, para-toluenesulfonic acid, and inorganic salts such as zinc acetate, or zinc borate. The phenol is preferably phenol itself, but a portion of the phenol can be substituted with cresols, xylenols, alkyl substituted phenols such as ethyl phenol, propyl phenol and mixtures thereof. Other phenols having unsubstituted ring positions ortho and para to the phenolic hydroxyl group, such as 3,5-xylen-l-ol and resorcinol, may be used to replace all or part of the phenol. The aldehyde is preferably formaldehyde, but other aldehydes such as acetaldehyde, benzaldehyde and furfural can also be used to partially or totally replace the formaldehyde.

The reaction of the aldehyde and phenol is carried out at the molar ratio of 1 mole of the phenol to about 0.30 to about 0.88 moles of the aldehyde. For practical purposes, phenolic novolacs generally do not harden upon heating, but remain soluble and fusible unless a hardener (curing agent) is present.

As described above, the novolac resin may be prepared using any of the catalysts commonly employed for this purpose. Thus the novolac may be a conventional acid- catalyzed novolac, in which the greater part of the phenolic nuclei are linked ortho-para or para-para, or may be a so-called "high ortho" novolac, in which there is preferential ortho- ortho linkage of the nuclei and which are prepared using an ortho-directing catalyst.

As stated above, the phenol and the aldehyde are reacted together in a molar ratio of less than 1 mole of aldehyde to each mole of the phenol. In general, the aldehyde will not be used in a molar ratio to phenol of less than 0.3:1. Preferably, however, the aldehyde used is formaldehyde and we prefer to use formaldehyde in an amount in the range of from 0.3 to 0.88, more preferably from 0.4 to 0.88, mole per mole of the phenol. Amounts of formaldehyde in excess of the maximum ratio indicated will tend to cause premature gelation of the resin. In the case of the high-ortho novolacs, the maximum useful ratio is about 0.75 mole of formaldehyde per mole of phenol and we prefer not to exceed 0.72 mole. In either case, proportions of formaldehyde below about 0.3 mole per mole of phenol are uneconomic and unnecessary because of the increased level of phenol that remains unreacted.

In preparing a high-ortho novolac, an ortho-directing catalyst, such as a salt of a bivalent metal, is typically employed in a proportion of from 0.1 to 5, usually from 0.4 to 1.2, parts for every 100 parts of the selected phenol by weight on an anhydrous basis. In the case of an acid-catalyzed novolac resin, it is only necessary to employ sufficient of the acidic material to obtain a satisfactory rate of resinification and the proportion required will vary with the type of acid used. In the case of the strong mineral acids, such as sulfuric acid or hydrochloric acid, this will generally be in the range of from 0.02 to 1.0%, and preferably from 0.1 to 0.6%, by weight based on the weight of the phenol employed. With organic acids, such as oxalic acid or maleic anhydride, it is typical to use amounts in the range of from 0.1 to 10%, and preferably from 1 to 5%, by weight based on the weight of the phenol employed. Methods for the preparation of acid-catalyzed novolac resins are well known. The high-ortho phenolic novolacs referred to herein may be prepared in any of the known ways. It is preferred, however, to employ, as catalysts in their preparation, salts of divalent electropositive metals, such as zinc acetate, zinc borate, manganese borate, nickel borate, calcium acetate, manganese acetate, lead acetate and zinc benzoate.

The novolac resins formed, whether they be acid-catalyzed or high -ortho resins, may be treated, when the reaction is substantially complete, to remove unreacted phenol. This may most conveniently be accomplished by steam distillation, but other methods of removing unreacted phenol, such as precipitation of the resin from solution and washing of the precipitate prior to drying, may be employed.

Part Two Binder Component The part two binder component may be a polymeric isocyanate in a solution of organic solvents and/or plasticizers. One preferred cold-box part two binder component, useful in embodiments of the present invention, is SIGMA CURE 7516, made and sold by Borden Chemical, Inc., Louisville, Kentucky. This binder component has a viscosity of about 29 cps, and a solids content of about 80 %. A preferred no-bake part two binder component, useful in embodiments of the present invention, is SIGMA SET 6400, made and sold by Borden Chemical, Inc., Louisville, Kentucky. This binder component has a viscosity of about 20 cps, and a solids content of about 70%. Isocyanates

The isocyanate component which can be employed in a binder according to the principles of the present invention may vary widely and includes polyisocyanates. As defined herein, polyisocyanates includes isocyanates having such functionality of 2 or more, e.g., diisocyanates, triisocyanates, etc. Exemplary of the useful isocyanates are organic polyisocyanates such as tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, and mixtures thereof, particularly crude mixtures thereof that are commercially available. Other typical polyisocyanates include methylene-bis-(4-phenyl isocyanate), n-hexyl diisocyanate, naphthalene-l,5-diisocyanate, cyclopentylene- 1,3 -diisocyanate, p-phenylene diisocyanate, tolylene-2,4,6-triisocyanate, and triphenylmethane-4,4^,,4"-triisocyanate. Higher isocyanates are provided by the reaction products of (1) diisocyanates and (2) polyols or polyamines and the like. In addition, isothiocyanates and mixtures of isocyanates can be employed. Also contemplated are the many impure or crude polyisocyanates that are commercially available. Especially preferred for use in the invention are the polyaryl polyisocyanates. The preferred polyisocyanate may vary with the particular system in which the binder is employed.

Solvents / Plasticizers As discussed above, the part one binder component and the part two binder component are typically dissolved in solvents and/or plasticizers (hereinafter generally referred to as solvents). The solvents provide component solvent mixtures of desirable viscosity and facilitate coating foundry aggregates with the part one and part two binder components. While the total amount of a solvent can vary widely, it is generally present in a composition of this invention in a range of from about 5% to about 70% by weight, based on the total weight of the part one binder component, and is preferably present in a range of from about 20% to about 60% by weight. With respect to the part two binder component, the solvent is generally present in a range of from about 1% to about 50% by weight, based on the total weight of the part two binder component, and is preferably present in a range of from about 5% to about 40% by weight. The solvents employed in the practice of this invention are generally hydrocarbon and polar organic solvents such as organic esters. Typically, the part one component may contain a mixture of hydrocarbon and polar solvents, while, typically, the part two component contains hydrocarbon solvents. Suitable exemplary hydrocarbon solvents include aromatic hydrocarbons such as benzene, toluene, xylene, ethyl benzene, high boiling aromatic hydrocarbon mixtures, heavy aromatic naphthas and the like. One hydrocarbon solvent useful in compositions made according to the principles of the present invention is SURE- SOL 150, available form Koch Chemical Company, Corpus Christi, Texas. Another hydrocarbon solvent useful in compositions made according to the principles of the present invention is SURE-SOL 205, also available from Koch Chemical Company, Corpus Christi, Texas. A biphenyl compound or a mixture of biphenyl compounds, may be used as an additive per se or as a substitute for a portion or part of the solvents. Preferably the biphenyl substitute is a mixture of substituted lower alkyl (Ci - C₆) compounds. A preferred composition comprises a mixture of compounds having di- and tri- substitution sold by Koch Chemical Company of Corpus Christi, Tex., as SURE-SOL 300, which is a mixture of diisopropylbiphenyl and triisopropylbiphenyl compounds. Another preferred biphenyl composition comprising a mixture of substituted biphenyls, is NYCEL, available from Crowley Chemical Company, New York, New York. Paraffinic oil may also be used and may be any of a number of viscous pale to yellow conventional refined mineral oils. For example white mineral oils may be employed in the present invention. The paraffinic oil may be in the phenolic resin component, the isocyanate component, or both components. A preferred paraffinic oil is SEMTOL 70, manufactured by Witco Chemical Co., New York, N.Y. A variety of ester-functional solvents are useful in embodiments of the present invention. Organic mono esters (long-chain esters), dibasic acid ester and/or fatty acid ester blends increase the polarity of the formulation. One preferred dibasic ester is DBE-2, a mixture of dimethyl glutarate and dimethyl adipate, and available from DuPont, Wilmington, Delaware. Other preferred dibasic esters may include mixtures of dimethyl esters of adipic, glutaric and succinic acids. Yet another preferred ester-functional solvent is dioctyl adipate, or DOA. Long-chain esters, such as glyceryltrioleate, are also useful in the embodiments of the present invention. The aliphatic "tail" of such an ester is compatible with non-polar components, while the ester "head" of the ester is compatible with the polar components. The use of a long-chain ester thus allows a balancing of polar character which facilitates the incorporation of non-polar component into a more polar system.

Although the solvents employed in combination with either the part one binder component or the part two binder component do not, to any significant degree, enter into the reaction between parts one and two, they can affect the reaction. Thus, the difference in polarity between a polyisocyanate and a polyol restricts the choice of solvents (and plasticizers for that matter) in which both part one and part two components are compatible. Such compatibility is necessary to achieve complete reaction and curing of the binder composition.

Coupling Agents and Additives Silanes are commonly added to phenolic foundry resins to improve the adhesion to the sand and the tensile strengths of the molds and cores produced from the resins. Amounts as low as 0.05% by weight, based on the weight of the part one or part two binder components, have, been found to provide significant improvements in tensile strength. Higher amounts of silane can generate greater improvements in strength up to quantities of about 0.6% by weight or more. The silanes are used in a quantity sufficient to improve adhesion between the resin and aggregate. Typical usage levels of these silanes are 0.1 to 1.5% based on resin weight. Useful silanes include γ-aminopropyltriethoxysilane, 2-(3,4- epoxycyclohexyl)ethyl trimethoxysilane, bis(trimethoxysilylpropyl)ethylenediamine, N- trimethoxysilylpropyl-N,N,N-trimethylammonium chloride and secondary amino silane. In the practice qf this invention, additives normally utilized in foundry manufacturing processes can also be added to the compositions during the sand coating procedure. Such additives include materials such as iron oxide, clay, carbohydrates, potassium fluoroborates, wood flour and the like. Catalysts

As previously noted above, the compositions of this invention can be cured by both the cold-box and no-bake processes. The compositions are cured by means of a suitable catalyst. While any suitable catalyst for catalyzing the reaction between the part one binder component and part two binder component may be used, it is to be understood that when employing the cold-box process, the catalyst employed is generally a volatile catalyst. On the other hand, where the no-bake process is employed, a liquid catalyst is generally utilized. Moreover, no matter which process is utilized, that is, the cold-box or the no-bake process, at least enough catalyst is employed to cause substantially complete reaction of the part one binder component and the part two binder component. Liquid amine catalysts and metallic catalysts employed in the no-bake process may be in either part one and/or part two binder components or added to a mixture of parts 1 and 2. In the cold-box process, tertiary amine catalysts are employed by being carried by an inert gas stream through a molded article until curing is accomplished.

Preferred exemplary catalysts employed when curing the compositions of this invention by the cold-box process are volatile basic catalysts, e.g., tertiary amine gases, which are passed through a core or mold generally along with an inert carrier, such as air or carbon dioxide. Exemplary volatile tertiary amine catalysts which result in a rapid cure at ambient temperature that may be employed in the practice of the present invention include trimethyl-amine, triethylamine and dimethylethylamine and the like. On the other hand, when utilizing the compositions of this invention in the no-bake process, liquid tertiary amine catalysts are generally and preferably employed. Exemplary liquid tertiary amines which are basic in nature include those having a pKb value in a range of from about 4 to about 11. The pK_b 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 liigher the number is, the weaker the base. Bases falling within the mentioned range are generally, organic compounds containing one or more nitrogen atoms. Preferred among such materials are heterocyclic compounds containing at least one nitrogen atom in the ring structure. Specific examples of bases which have a pKb value within the range mentioned include 4-alkyl-pyridines wherein the alkyl group has from 1 to 4 carbon atoms, isoquinoline, arylpyridines, such as phenyl propyl pyridine ("PPP"), acridine, 2-methoxypyridine, pyridazines, 3-chloropyridine, and quinoline, N-methylimidazole, N-vinylimidazole ("NIDZ"), 4, 4-dipyridine, 1-methylbenzimidazole and 1, 4-thiazine. Additional exemplary, suitable preferred catalysts include, but are not limited to, tertiary amine catalysts such as Ν, Ν-dimethylbenzylamine,triethylamine,tribenzylamine,Ν, N-dimethyl-, 3-propanediamine, N, N-dimethylethanolamine and triethanolamine. It is to be understood that various metal organic compounds can also be utilized alone as catalysts or in combination with the previously mentioned catalyst. Examples of useful metal organic compounds which may be employed as added catalytic materials are cobalt naphthenate, cobalt octoate, dibutyltin dilaurate, stannous octoate and lead naphthenate and the like. When used in combinations, such catalytic materials, that is the metal organic compounds and the amine catalysts, may be employed in all proportions with each other.

It is further understood that when utilizing the compositions of this invention in the no-bake process, the amine catalysts, if desired, can be dissolved in suitable solvents such as, for example, the hydrocarbon solvents mentioned above. The liquid amine catalysts are generally employed in a range of from about 0.5% to about 15% by weight, based on the weight of the part one binder component present in a composition in accordance with the invention. When employing a binder composition of this invention in the no-bake process, the curing time can be controlled by varying the amount of catalyst added. In general, as the amount of catalyst is increased, the cure time decreases.

Curing of the binders of the present invention generally takes place at ambient temperature without the need for subjecting the compositions to heat. However, in usual foundry practice preheating of the sand is often employed to raise the temperature of the sand to accelerate the reactions and control temperature and thus, provide a substantially uniform operating temperature on a day-to-day basis. The sand is typically preheated to from about 30° F up to as high as 120° F and preferably up to about 75° F to 100° F. However, such preheating is neither critical nor necessary in carrying out the practice of this invention. Aggregate

The aggregate material commonly used in the foundry industry include silica sand, construction aggregate, quartz, chromite sand, zircon sand, olivine sand, or the like. Reclaimed sand, that is sand that may have been previously bonded with a phenolic urethane binder may also be used.

Sand sold under the product designation F-5574, available from Badger Mining Corporation, Berlin, Wisconsin, 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, Illinois, is also useful. Sand sold under the product designation Nugent 480, available from Nugent Sand Company, Muskegon, Michigan, may also be used. As known in the art, the sand type will affect the strength development of the bound aggregate. Foundry Cores and Molds

In general, the process for making foundry cores and molds in accordance with an embodiment of this invention comprises admixing aggregate material with at least a binding amount of the part one binder component and the part two binder component. A mixture of a fluoride bearing acid and a silicon or boron compound may be added to the aggregate material. Preferably, the process for making foundry cores and molds in accordance with this invention includes admixing aggregate material with at least a binding amount of a modified part one binder component containing methyl benzoate.

In general, the process for making foundry cores and molds in accordance with this invention comprises admixing aggregate material with at least a binding amount of the part one and part two binder components. Preferably, the process for making foundry cores and molds in accordance with this invention comprises admixing aggregate material with at least a binding amount of a modified part one binder component of the present invention. A part two binder component is added and mixing is continued to uniformly coat the aggregate material with the part one and part two binder components. In the no-bake process, a sufficient amount of catalyst is added to catalyze the reaction between the components. The admixture is suitably manipulated, as for example, by distributing the same in a suitable core box or pattern. In the cold-box process, a sufficient amount of catalyst is applied to the uncured core or mold to catalyze the reaction between the components. The admixture is cured forming a shaped product. There is no criticality in the order of mixing the constituents with the aggregate material except where a vaporous catalyst is used, in which case the catalyst is passed through the admixture after it is shaped. On the other hand, it is preferred to add the catalyst, in the case of the no-bake process, as the last constituent of the composition so that premature reaction between the components does not take place. The components may be mixed with the aggregate material either simultaneously or one after the other in suitable mixing devices, such as mullers, continuous mixers, ribbon blenders and the like, while continuously stirring the admixture to insure uniform coating of aggregate particles. It is to be further understood that as a practical matter, the phenolic resole of the part one binder component can be stored separately and mixed with solvent just prior to use of or, if desirable, mixed with solvent and stored until ready to use. Such is also true with the polyisocyanate of the part two binder component. As a practical matter, the part one and part two binder components should not be brought into contact with each other until ready to use to prevent any possible premature reaction between them.

When the admixture is to be cured according to cold-box process, the admixture after shaping as desired, is subjected to gassing with a vaporous catalyst as described above. Sufficient vaporous catalyst is passed through the shaped admixture to provide substantially complete reaction between the components. The flow rate of the vaporous catalyst is dependent, of course, on the size of the shaped admixture as well as the amount of binder therein.

In contrast, however, when the admixture is to be cured according to no-bake process, the catalyst is generally added in liquid form to the aggregate material with the part one binder component. The admixture is then shaped and simply permitted to cure until reaction between the components is substantially complete, thus forming a shaped product such as a foundry core or mold. On the other hand, the liquid catalyst may also be admixed with the part one binder component prior to coating of the aggregate material with the components.

The quantity of binder can vary over a broad range sufficient to bind the refractory on curing of the binder. Generally, such quantity will vary from about 0.4 to about 6 weight percent of binder based on the weight of the aggregate and preferably about 0.5% to 3.0% by weight of the aggregate. The binder compositions of this invention may be employed by admixing the same with a wide variety of aggregate materials. When so employed, the amount of binder and aggregate can vary widely and is not critical. On the other hand, at least a binding amount of the binder composition should be present to coat substantially, completely and uniformly all of the sand particles and to provide a uniform admixture of the sand and binder. Thus, sufficient binder is present so that when the admixture is conveniently shaped as desired and cured, there is provided a strong, uniform, shaped article which is substantially uniformly cured throughout, thus minimizing breakage and warpage during handling of the shaped article, such as, for example, sand molds or cores, so made.

In testing embodiments of the present invention, tensile strengths of the cores prepared as noted above were determined using a Thwing-Albert Tensile Tester (Philadelphia, Pa.). This device consists of jaws that accommodate the ends of a "dog-bone- shaped" test core. A load is then applied to each end of the test core as the jaws are moved away from each other. The application of an increasing load continues until the test core breaks. The load at this point is termed the tensile strength, and it has units of psi (pounds per square inch). The advantages of this invention and its preferred embodiments will be demonstrated more fully by the following Examples, that demonstrate the practice of the invention. In these Examples, and elsewhere throughout the specification, parts and percentages are by weight.

Test Cores - Cold-box Examples Test cores were prepared by the following method: to a quantity of about 2.5 kg washed and dried aggregate material was added an amount of either a part one binder component or a modified part one binder component of the present invention and the mixture was stirred for about one minute in a Hobart Kitchen Aid Mixer. Next, a part two binder component was added to the mixture, which was then further mixed for another one and one- half minutes. This mixture was then used to form standard American Foundrymen's

Society's 1-inch dog bone tensile specimens in a standard core box employing a laboratory core blower. The cores were cured at room temperature using vaporous triethyl amine catalyst and the samples were broken at various time intervals after the mix was made. The cores were stored in an open laboratory environment, at ambient temperatures, until tested, or, as noted, the cores were stored in humidity chambers providing a specified humidity. Tensile strength measurements were made as described above. Average values for three tensile strength measurements were typically recorded. For the controls, the average results of three separate sand tests are reported. For the comparative tests, the results are for just one sand test. In the testing of cold-box binders, the tensile strength development was determined both as a function of core age and as a function of sand mix age. This latter test is referred to as bench life testing. In bench life testing, a portion of the sand/binder mixture is allowed to age under ambient conditions. At periodic intervals after the mixture has been made, portions of the sand/binder mixture are used to make cores for testing of tensile strength. It is typical that some degradation of tensile strength of a cured core will occur as a function of the age of the sand/binder mixture.

Test Cores - No-bake Examples

Test cores were prepared by the following method: to a quantity of about 2.5 kg washed and dried aggregate material was added an amount of either a part one binder component or a modified part one binder component of the present invention and the mixture was stirred for about one minute in a Hobart Kitchen Aid Mixer. Next, a part two binder component and a liquid amine catalyst were added to the mixture. This mixture was stirred for an additional 30 seconds and then used immediately to form standard American Foundrymen's Society's 1-inch dog bone tensile specimens in a Dietert 696 core box. The cores were cured at room temperature using a liquid amine catalyst and the samples were broken at various time intervals after the mix was made. The cores were stored in an open laboratory environment, at ambient temperatures, until tested, or, as noted, the cores were stored in humidity chambers providing a specified humidity. Tensile strength measurements were made as described above. Average values for three tensile strength measurements were typically recorded. For the controls, the average results of three separate sand tests are reported. For the comparative tests, the results are for just one sand test. The humidity chambers used in both the cold-box and no-bake testing are typical of the type of chambers known in the art. Glass chambers, generally glass dessicators, are used as the humidity chambers. Either pure water or solutions of water and glycerol are used to generate a relatively constant humidity environment in the glass chambers.

Example 1 In this example, the effect of adding varying amounts of methyl benzoate on tensile strength was determined. The part one binder of the control and tests as shown in the table, infra, describe the percentage of each component in the part one binder. The control established for the part one binder uses no methyl benzoate. Likewise, the part two binder component used contains no methyl benzoate. The test results listed are the average of three sand test results. The aggregate used was Wedron 530. The total binder used was 1.25%, based on the weight of sand. The ratio of part one binder component to part two binder component was 55:45. For both the control and the example, the part two binder component was SIGMA CURE 6400. Both part one and part two components contained a small amount of an organosilane.

Table 1. Tensile Strength Improvement In No-bake Process

P Paartrt oonnee C Coonnttrrooll 11 Example 1 Example 2

P Phheennoolliicc rreessoollee rreessiinn 5 577..7777 57.77 57.77

S SUURREE SSOOLL 115500 2 277..3399 27.39 27.39

M Meetthhyyll BBeennzzooaattee 0 0..0000 10.83 10.83

D DBBEE--22 1 144..4444 3.61 0.00

D DOOAA 0 0..0000 0.00 3.61 oorrggaannoossiillaannee 0 0..4400 0.40 0.40

P Paartrt ttwwoo 6 6440000 6400 6400

Catalyst Type PPP PPP PPP

Strip Times 5'28" 4'25" 3'55"

Tensile Strength, psi

10 min. 159 174 153

1 hour 261 250 217

24 hours 338 311 302

Tensile Strength, psi, at 100% Relative Humidity

24 hours 93 92 101

The data of table 1 demonstrates an unexpected improvement in tensile strength of 9.4%). Furthermore, the data demonstrates a significant and unexpected acceleration of strip time, the improvement being over 23%). Cores made according to the principles of the present invention, and a control, are subsequently removed from the core box. Following removal from the core box., the tensile strength was determined at the time periods shown in Table 1. Moreover, as described in table 1, cores made according to the principles of the present invention, and a control, were stored in a humidity chamber providing an environment of 100% relative humidity for 24 hours. At the end of this time period the cores tensile strength was determined. The data of table 1 also demonstrate how the low cost method of using methyl benzoate improves tensile strength and humidity resistance.

Example 2 In this example, as in example 1 above, the effect of combining varying amounts of methyl benzoate a part one binder component, a part two binder component, and a catalyst on tensile strength was determined. The control included a binder employing no methyl benzoate and was the same control as used in Example 1. In the example, 10.83% of methyl benzoate, based on the total weight of the part one binder component was used, and was formulated as described for Example 1 above. The test results listed are the average ofthree sand test results. The aggregate used was Wedron 530. The total binder used was 1.25%, based on the weight of sand. The ratio of part one binder component to part two binder component was 55:45.

Table 2. Tensile Strength Improvement In No-bake Process

Part one Control 1 Example 1 Part two 6400 6400

Catalyst Type PPP mixture of PPP and NIDZ

Tensile Strength, psi

1 minute 146 186 l hour 232 283

24 hours 246 308

Tensile Strength, psi, at 100%) Relative Humidity

24 hours 54 116

Surprisingly, the data shows an enhancement of tensile strength in the first minute following removal of the core from the core box of 27.4%. Furthermore, the data of table 2 demonstrates an unexpected improvement of in humidity resistance by as much as 100%. The data of tables 1 and 2 also demonstrate that different catalysts are equally effective in providing these improvements in humidity resistance and tensile strength. As described above, cores made according to the principles of the present invention, and a control, were stored in a humidity chamber providing an environment of 100% relative humidity for 24 hours. At the end of these time periods the cores tensile strength was determined. Example 3

In this example, the effect of adding varying amounts of methyl benzoate to the part one binder component of a phenolic urethane cold-box binder was determined. The control included a binder employing no methyl benzoate. In this test, 5.8%) of methyl benzoate, based on the total weight of the part one binder component was used. The test results listed are the average ofthree sand test results. The aggregate used was Wedron 530. The total binder used was 1.0%, based on the weight of sand. The ratio of part one binder component to part two binder component was 55:45. The control and the example used the part two binder component SIGMA CURE 7516. Both part one and part two components contained a small amount of an organosilane. The example used a modified SIGMA CURE 7121, in which the methyl benzoate replaced an equal amount of polar solvent.

Table 3. Tensile Strength Improvement In Cold-box Formulations

Part one Control 2 Example 3

Phenolic resole resin 57.50 57.50

SURE SOL 205 21.10 21.10

DBE-2 8.00 2.20

Methyl benzoate 0.00 5.80

NYCEL 7.00 7.00

Fatty acid ester 6.00 6.00

Organosilane 0.40 0.04

Part two 7516 7516

Tensile Strength, psi

1 minute 128 158

1 hour 201 187

24 hours 227 205 Tensile Strength, psi, at 100%> Relative Humidity

24 hours 66 44

The data of table 3 demonstrates an unexpected improvement in tensile strength during the first minute by as much as 20%.

Example 4 - Effect of Methyl Benzoate on Anti-Warp Characteristics

In this example, the effect of adding methyl benzoate to part one of a urethane binder component on warp and sag characteristics was determined. The control included a binder employing no methyl benzoate and a PPP-type catalyst. In the control, no methyl benzoate was used. In the example, 10.83% methyl benzoate, based on the total weight of the part one binder component, was used. The test results listed are the average ofthree sand test results. The aggregate used was Wedron 530. The total binder used was 1.25%, based on the weight of sand. The ratio of part one binder component to part two binder component was 55:45. Both part one and part two components contained a small amount of an organosilane. To test the anti-warp characteristics of a urethane binder, a common sand mix is made. The sand-binder mix is then hand-rammed into a mold that is configured for making warp test bars. The warp test bars are 9 inches long by ^lλ inch thick by 1 inch wide. In the warp test, the bars are measured from the estimated time of cure, and then removed from the mold at time intervals and placed on a fixture that supports the bars simply at the bars ends. The bars are then allowed to sag or warp to their furthest extent over time. The amount of sag is then measured at various time intervals and reported as the warpage.

Table 4. Warp/Sag Improvement In No-bake Process

Part one Control 1 Control 1 Example 1

Part two 6400 ^• 6400 6400

Catalyst Type PPP VIDZ mixture of PPP and VIDZ

Time After Strip WARP/SAG (mm)

3 minutes 3.5 2.5 1.0

5 minutes 2.0 1.0 0.0

7 minutes 1.0 0.5 0.0

The data of table 4 demonstrates a remarkable improvement in anti-warp characteristics, bringing the amount of warpage down to zero, thus realizing over a 150% decrease in warpage. Previously, as the control demonstrates, after 3 minutes nearly 3.5 mm of sag is found in the core or mold. Whereas, in the present invention, with methyl benzoate added to the part one binder component, only 1.0 mm of sag is measured in the core or mold. Furthermore, the control shows that, even after 7 minutes, the core or mold continues to sag approximately 1.0 mm. As the table shows, with the new improvement, no sag or warp is measured, even after five minutes. This new anti-warp characteristic provides more dimensional reliability for urethane binder foundry cores and molds. The data of table 4 also demonstrates that phenolic urethane binder systems made according to the principles of the present invention do not require the use of the more basic, and more costly, NIDZ type catalyst to improve warp resistance. A lower cost mixture of PPP and NIDZ may be used to produce surprising and unexpected improvements in warp resistance.

Example 5

In the following example, the control of example 1 was used in sand tests in comparison to a phenolic urethane binder made according to the principles of the present invention which used only methyl benzoate as the polar solvent. The part one binder component of the phenolic urethane binder made according to the principles of the present invention did not use an organosilane coupling agent.

Table 5. Tensile Strength Improvement In Νo-bake Process

Part one Control 1 Example 5

Phenolic resole resin 57.77 57.77 SURE-SOL 150 27.39 27.39

Methyl Benzoate 00.00 14.84

DBE-2 14.44 00.00 organosilane 00.40 00.00

Part two 6400 6400

Catalyst Type PPP PPP

Strip Times 7'46" 5 '20"

Tensile Strength, psi

10 min. 153 198

1 hour 282 286

24 hours 351 352

Tensile Strength, psi, at 100% Relative Humidity

24 hours 77 81

In the tests of table 5, equal amounts of the same PPP-type catalyst were used for both the control and the part one binder of Example 5. As shown by the data of table 5, the phenolic urethane binder made according to the principles of the present invention yields a surprising and unexpected improvement in strip time of more than 45% and in 10 minute tensile strength of more than 29%o.

A review of the results provided in example 1 through 5 above also demonstrates several additional benefits of the present invention. The use of methyl benzoate in the phenolic urethane binders of the present invention, does not adversely affect the other strength parameters of cured cores and molds. In fact, it can be seen that tensile strength of cores made according to the principles of the present invention can be greater than the corresponding strengths of the control cores. Also, the humidity resistance demonstrates a similar improvement. Accordingly, the present invention provides improved humidity resistance and tensile strength for foundry cores and mold without sacrificing other important properties of such cores and molds.

There has been provided in accordance with the present invention, an improved phenolic urethane binder composition useful for binding foundry cores and molds.- There has also been provided in accordance with the present invention, a method for improving the strength and humidity resistance of a phenolic, urethane resin and the foundry cores and molds made using such an improved binder composition. There is further provided in accordance with the present invention, a method for improving anti-warp characteristics of a phenolic urethane binder and the foundry cores and molds made using such composition. While the invention has been described with specific embodiments and many alternatives, modifications and variations will be apparent to those skilled in the art-in light of the foregoing description. Accordingly, it is intended to include all such alternatives, modifications and variations set forth within the spirit and scope of the appended claims.

Claims

What is claimed is:

1. A binder component for a urethane foundry binder comprising: a phenolic resin; and methyl benzoate; wherein the binder component may react with a polymeric isocyanate to form the urethane foundry binder.

2. The binder component of Claim 1 wherein the methyl benzoate is present in an amount greater than about 1 %> of the total weight of the binder component.

3. The binder component of Claim 2 wherein the methyl benzoate is present in an amount of from about 1% to about 25%> of the total weight of the binder component.

4. The binder component of Claim 1 wherein the phenolic resin is a resole.

5. The binder component of Claim 1 wherein the phenolic resin is a novolac.

6. The binder component of Claim 1 wherein the phenolic resin is a mixture of resole and novolac.

7. The binder component of Claim 1 further comprising a polar solvent.

8. The binder component of Claim 1 further comprising a hydrocarbon solvent.

9. A part one urethane binder component for a urethane foundry binder comprising the product obtained by mixing: a phenolic resin; and methyl benzoate.

10. The product of Claim 9 wherein the methyl benzoate is present in an amount greater than about 1% of the total weight of the product.

11. The product of Claim 10 wherein the methyl benzoate is present in an amount ranging from about 1% to about 25%> of the total weight of the product.

12. The product of Claim 9 wherein the phenolic resin is a resole.

13. A polyurethane binder system comprising : i) a phenolic resin solution; ii) an isocyanate solution, the solutions i) and ii) present in amounts to produce a cured binder in the presence of a suitable catalyst; iii) methyl benzoate; iv) a suitable catalyst; and v) foundry aggregate.

14. The composition of Claim 13 wherein the methyl benzoate is present in an amount greater than about 1 % of the total weight of the phenolic resin solution.

15. The composition of Claim 14 wherein the methyl benzoate is present in an amount ranging from about 1% to about 25% of the total weight of the phenolic resin solution.

16. The composition of Claim 13 wherein the phenolic resin solution comprises a resole.

17. The composition of claim 13 wherein the phenolic resin solution includes a polar solvent.

18. The composition of claim 13 wherein the phenolic resin solution includes a hydrocarbon solvent.

19. A method for improving tensile strength of a cured foundry core comprising the steps of: a. mixing together: i) a foundry aggregate; ii) at least two foundry binder components comprising a phenolic resin component and an isocyanate component; and iii) methyl benzoate; ^' b. molding the mixture; and c. curing the mixture.

20. The method of claim 19 wherein the mixture of foundry aggregate and foundry binder components includes a foundry binder catalyst.

21. The method of Claim 19 wherein the methyl benzoate and the phenolic resin component are pre-mixed.

22. The method of claim 19 wherein the foundry core is cured by the no-bake method.

23. The method of claim 19 wherein the foundry core is cured by the cold-box method.

24. A method for improving warp resistance of a cured foundry core comprising the steps of: a. mixing together: i) a foundry aggregate; ii) at least two foundry binder components comprising a phenolic resin component and an isocyanate component; and iii) methyl benzoate; b. molding the mixture; and c. curing the mixture.

25. The method of claim 24 wherein the mixture of foundry aggregate and foundry binder components includes a foundry binder catalyst.

26. The method of Claim 24 wherein the methyl benzoate and the phenolic resin component are pre-mixed.

27. The method of claim 24 wherein the foundry core is cured by the no-bake method.

28. The method of claim 24 wherein the foundry core is cured by the cold-box method.

29. A method for improving humidity resistance of a cured foundry core comprising the steps a. mixing together: i) a foundry aggregate; ii) at least two foundry binder components comprising a phenolic resin component and an isocyanate component; and iii) methyl benzoate; b. molding the mixture; and c. curing the mixture.

30. The method of claim 29 wherein the mixture of foundry aggregate and foundry binder components includes a foundry binder catalyst.

31. The method of Claim 29 wherein the methyl benzoate and the phenolic resin component are pre-mixed.

32. The method of claim 29 wherein the foundry core is cured by the no-bake method.

33. The method of claim 29 wherein the foundry core is cured by the cold-box method.

34. A method for accelerating the cure of a urethane foundry binder comprising the steps of: a. mixing together: i) a foundry aggregate; ii) at least two foundry binder components comprising a phenolic resin component and an isocyanate component; and iii) methyl benzoate; b. molding the mixture; and c. curing the mixture.

35. The method of claim 34 wherein the mixture of foundry aggregate and foundry binder components includes a foundry binder catalyst.

36. The method of Claim 34 wherein the methyl benzoate and the phenolic resin component are pre-mixed.

37. The method of claim 34 wherein the foundry core is cured by the no-bake method.

38. The method of claim 34 wherein the foundry core is cured by the cold-box method.