GB2024232A

GB2024232A - Urethane binder for no-bake and cold-box foundry cores and moulds

Info

Publication number: GB2024232A
Application number: GB7918769A
Authority: GB
Original assignee: Ashland Oil Inc
Current assignee: Ashland LLC
Priority date: 1978-06-14
Filing date: 1979-05-30
Publication date: 1980-01-09
Also published as: DE2923131A1; GB2024232B; CH647965A5; DK170551B1; NO791925L; NO155997C; DE2923131C2; SE7905016L; SE446098B; NO155997B; SE446098C; DK240879A

Abstract

Binder compositions suitable for manufacturing foundry cores and moulds by the "no-bake" and "cold- box" process comprise a liquid polyisocyanate, a polyol component which comprises either an aromatic amine polyol or an adduct of ammonia and an alkylene oxide, and optionally a gaseous tertiary amine curing agent. Foundry cores and moulds for casting light-weight metals are prepared using a binder composition comprising a liquid polyisocyanate, an amine polyol, particularly one as defined above, and optionally a gaseous tertiary amine curing agent. The cores and moulds produced exhibit excellent shakeout properties.

Description

SPECIFICATION Urethane binder compositions for no-bake and cold box foundry operations This invention relates to resinous binder compositions which are admixtures of amine-based polyols and polyisocyanates. These compositions may be cured by a gaseous catalyst. In another aspect this invention relates to curable urethane binder compositions which are useful for binding particulate solids. In particular the invention relates to binders of the no bake and of the cold box type, which utilize an amine polyol. The binders are capable of bonding sand or other foundry aggregate to form moulds or cores for casting of metals, especially aluminum and other lightweight metals which are cast at relatively low temperature. The cores and moulds made using these binders demonstrate superior collapsibility or shakeout when used at low casting temperatures.

Urethane cold box binders for use in bonding aggregates useful as foundry cores and molds are known in the art. U. S. Patent No. 3,409,579 is an example of such a cold box binder composition and the use thereof to make cores and molds for foundry applications.

A cold box binder system for use in foundries is now disclosed which utilizes an amine polyol as a component of the binder composition. It is believed that utilization of an amine polyol in a cold box system is in itself an advancement in the art of foundry binders.

Further, Urethane No Bake binders for use in bonding aggregates useful as foundry cores and molds are known in the art. U.S. Patent No. 3,676,392 is an example of such a No Bake binder composition and the use thereof to make cores and molds for foundry applications.

This invention is based in part upon the autocatalytic nature of amine polyols. A No Bake binder system for use in foundries is now disclosed which can be a two componenet system instead of a typical urethane No Bake System which utilizes at least three components.

Although the autocatalytic nature is a significant advancement, this invention is not limited to such a system but may also incorporate a catalyst in certain embodiments.

This invention also embodies another very important feature. A long felt need in the foundry industry has been a no bake and a cold box binder for making castings for light metals such as aluminum and magnesium. The no bake and cold box binders of the prior art were unable to provide cores and molds for casting these lightweight metals having the required core and mold properties as well as good shakeout.

When enough binder is used to achieve workable strength and abrasion resistance the cores and molds will not break down well at the casting temperatures of light metals. That is, they exhibited poor shakeout. An existing problem has been to find a binder that on the one hand produced strong, non-friable cores and molds and on the other hand, broke down well at the casting temperature of aluminum and magnesium to provide easy shakeout.

It is an object of this invention to provide a foundry binder composition using in admixture a polyol and a polyisocyanate, wherein the polyol is an amine polyol. The mixture may be cured with a gaseous catalyst.

The amine polyols of this invention are normally obtained as the reaction product of an amine and a alkylene oxide.

Another object of this invention is to provide urethane no bake and cold box binder compositions. It is further an object of this invention to provide urethane no bake and cold box binders which can be used to produce cores and molds which have strength and non-friability but still break down well at low casting temperatures, i.e. below the casting temperatures of ferrous metals. The cores and molds of this invention exhibit the combination of strength and easy shakeout at the casting temperatures of lightweight metals such as aluminum and magnesium.

It has been found that a urethane binder formed as the reaction product of a polymeric isocyanate and an amine-based polyol can be used to make cores and molds. The binder may be rapidly cured using a gaseous tertiary amine catalyst. It has been found that a polyol which is the reaction product of an amine compound and an alkylene oxide can be combined with a polymeric isocyanate to produce a no bake or a cold box binder which, upon mixing with sand or other suitable foundry aggregates and curing, forms cores and molds possessing excellent working characteristics, i.e. strength, abrasion resistance and non-friability.

These properties are coupled with excellent shake-out characteristics when used in casting non-ferrous metals. This combination of good working characteristics and excellent shakeout are especially significant and unique when the binder is used to make cores intended for use in low temperature casting. A catalyst may be used to harden the components of the binder system. Suitable catalysts for the cold box invention are gaseous tertiary amines or amines that can be introduced as a vapor. Trimethylamine, dimethylethylamine, and triethylamine are preferred catalysts. A catalyst is not necessarily a component of the no bake binder system. However, suitable catalysts can be utilized in the no bake binder invention and are preferred with certain amine polyols when a rapid cure is needed.

The resin compositions of the present invention find use as a twopart composition or system. Part one is the amine polyol. Part two is the polyisocyante. Both parts are in liquid form and are generally solutions with organic solvents. At the time of use, that is to say, when the urethane binder is formed, the amine polyol part and the polyiscocyanate part are combined and used for the intended application. In foundry application, i.e.

the use of the compositions as a binder for cores and molds, it is preferred to first admix one part with a foundry aggregate such as sand. Thereafter, the second component is added and after achieving a uniform distribution of binder on the aggregate, the resulting foundry mix is formed or shaped into the desired shape. The shaped product can immediately be set aside and will cure to form a core or mold at room temperature. The compositions of this invention are generally autocatalytic to a degree. That is, once the amine polyol and isocyanate.are combined the reactivity of the polyol with the isocyanate is such that the reaction proceeds rapidly enough that a catalyst is not needed. The degree of reactivity of the amine polyol and polyisocyanate is dependent upon the reactivity of the polyol.The shaped product may also be cured to form a core or mold by contacting the shape with a gaseous catalyst.

In spite of the fact that the compositions are autocatalytic, liquid amine catalysts and metallic catalysts known in urethane technology may be employed in the no bake version. It should be noted that in some cases the use of a catalyst with the amine polyol and polyisocyanate components is beneficial and preferred.

By selection of a proper catalyst, conditions of the core making process, for example work time and strip time, can be adjusted as desired. In commerical practice it may be necessary to use a catalyst with certain polyols to obtain desired production rates.

Gaseous amine catalysts known in cold box technology may also be employed. The actual curing step can be accomplished by suspending a tertiary amine in an inert gas stream and passing the gas stream containing the tertiary amine, under sufficient pressure to penetrate the molded shape, through the mold until the resin has been cured. The binder compositions of the present invention require exceedingiy short curing times to achieve acceptable tensile strengths, an attribute of extreme commercial importance.

Optimum curing times are readily established experimentally. Since only catalytic concentrations of the tertiary amine are necessary to cause curing, a very dilute stream is generally sufficient to accomplish the curing. However, excess concentrations of the tertiary amine beyond that necessary to cause curing are not deleterious to the resulting cured product. Inert gas streams, e.g. air, carbon dioxide or nitrogen, containing from 0.01 to 20% by volume of tertiary amine can be employed. Normally gaseous tertiary amines can be passed through the mold as such or in dilute form. Suitable tertiary amines are gaseous tertiary amines such as trimethylamine. However, normally liquid tertiary amines such as triethylamine are equally suitable in volatile form or if suspended in a gaseous medium and then passed through the mold.Although ammonia, primary amines and secondary amines exhibit some activity in casing a room temperature reaction, they are considerably inferior to the tertiary amines. Functionally, substituted amines such as dimethylethanolamine are included within the scope oftertiary amines and can be employed as curing agents. Functional groups which do not interfere in the action of the tertiary amine are hydroxyl groups, alkoxy groups, amino and alkylamino groups, ketoxy groups, thio groups, and the like.

The amine polyols used to form the urethane binder compositions of this invention are normally produced as the reaction product of an alkylene oxide and an amine compound. When the term "amine polyol" is used herein it is meant to identify such reaction products but is not limited specifically to such means of synthesis.

In general any polyol containing at least one or more tertiary amine groups are considered to be within the scope of the definition of "amine polyol". The alkylene oxides which are used to prepare the amine polyols are preferably ethylene oxide and propylene oxide. However, it appears feasible to use other alkylene oxides as well. The amount of alkylene oxide in moles to moles of amine compound is subject to considerable variation. It is believed that the degree of alkoxylation does not detract from the ability of the resultant amine polyol to function as a binder.

The amine compounds which react with alkylene oxides to yield the amine polyols useful in the binder composition constituting this invention include ammonia and mono and polyamino compounds with primary and secondary amino nitrogens. Specific examples include aliphatic amines such as primary alkyl amines, ethylene diamine, diethylene triamine and triethylene tetramine, cycloaliphatic amines, aromatic amines, such as ortho-, meta- and para- phenylene diamines, aniline-formaldehyde resins and the like.

Blends of the amine polyols listed above can also be utilized. In addition a blend of amine polyols with other polyols, i.e. nonamine polyols, is useful. In general it is belived that amine containing compounds which when alkoxylated yield a polyol with two or more reactive hydroxyl groups are useful in the compositions of this invention.

The nature of the polyol component utilized influencesthe conditions of the core-making process. In a cold-box process, that is a process where the resin coated sand is cured by gassing with an amine catalyst, an important property of the binder is its bench life. Bench life, which corresponds to work time in a no-bake system, is the amount of time during which resin-coated sand has utility. After a binder is distributed on an aggregate, the binder begins to react. After a certain amount of time the reaction proceeds to such extent that the resin-coated sand can no longer be used. The sand coated with the binder is then said to be "shot".

After the sand is coated with resin the amount of time before the sand mixture is "shot" is known as bench life in a cold-box system. It has been found that using aromatic initiated amine polyols results in an unexpected increase in the bench life of the resincoated sand. This unexpected result is of great utility and is considered to be important.

As mentioned above, it has been found that blending or mixing an amine polyol with another polyol, a polyhydroxyl compound capable of reacting with a polyisocyanate, has been found to be useful. This utility is especially apparent in out of the box strengths achieved after exposing the binder to the catalyst.

Especially preferred are hydroxy containing phenolic resins of U.S. Patent No. 3,485,797 known in the foundry industry as PEP resins.

The second component or package of the novel binder composition comprises an aliphatic, cycloaliphatic, or aromatic polyisocyanate having preferably from 2 to 5 isocyanate groups. If desired, mixutres of polyisocyanates can be employed. Isocyanate prepolymers formed by reacting excess polyisocyanate with polyhydric alcohol, e.g., a prepolymer of toluene diisocyanate and ethylene glycol, also can be employed.

Suitable polyisocyanates include the aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanates, and aromatic polyisocyanates such as 2,4- and 2,6-toluene diisocyanate, diphenylmethane diisocyanate, and the dimethyl derivatives thereof. Further examples of suitable polyisocyanates are 1 ,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and the methyl derivatives thereof, polymethylenepolyphenyl isocyanates, and the methyl derivatives thereof, chlorophenylene-2, 4-diisocyanate, and the like. Although all polyisocyanates react with the amine polyol to form a crosslinked polymer structure, the preferred polyisocyanates are aromatic polyisocyanates and particularly diphenylmethane diisocyanate, triphenymethane tiisocyanate, and mixtures thereof.

The polyisocyanate is generally employed in approximately a stoichiometric amount, that is in sufficient concentration to cause the curing of the amine polyol. However, it is possible to deviate from this amount within limits and in some case advantages may result. In general, the polyisocyanate will be employed in a range of 10 to 500 weight percent based on the weight of the amine polyol. Preferably, from 20 to 300 weight percent of polyisocyanate on the same basis is employed. The polyisocyanate is employed in liquid form.

Liquid polyisocyanates can be employed in undiluted form. Solid or viscous polyisocyanates are employed in the form or organic solvent solutions, the solvent being present in a range of up to 80% by weight of the solution.

Although the solvent employed in combination with either the amine polyol or the polyisocyanate or for both components does not enter to any significant degree into the reaction between the isocyanate and the amine polyol, it can affect the reaction. Thus the difference in the polarity between the polyisocyanate and the amine polyol restricts the choice of solvents in which both components are compatible. Such compatibility is necessary to achieve complete reaction and curing of the binder compositions of the present invention. Polar solvents of either the protic or aprotic type are good solvents for the amine polyol. It is therefore preferred to employ solvents or combinations of solvents where the solvent(s) for the polyol and for the polyisocyanate when mixed are compatible.In addition to compatibility the solvents for either the polyol or polyisocyanate are selected to provide low viscosity, low odor, high boiling point and interness.

Examples of such solvents are benzene, toluene, xylene, ethylbenzene, and mixtures thereof. Preferred aromatic solvents are solvents and mixtures thereof that have a high aromatic content and a boiling point range with a range of 280 to 725"F. The polar solvents should not be extremely polar such as to become incompatible when used in combination with the aromatic solvent. Suitable polar solvents are generally those which have been classified in the art as coupling solvents and include furfural, Cellosolve, glycoi diacetate, butyl Cellosolve acetate, isophorone and the like. It is possible some reactive polyols may also be used as a solvent. In addition it should be noted that water has been found to be a suitable solvent for the amine polyol under certain conditions.

The binder components are combined and then admixed with sand or a similar foundry aggregate to form the foundry mix or the foundry mix can also be formed by sequentially admixing the components with the aggregate. Methods of distributing the binder on the aggregate particles are well-known to those skilled in the art. The foundry mix can, optionally, contain other ingredients such as iron oxide, ground flax fibers, wood cereals, pitch, refractory flours, and the like. The aggregate, e.g. sand, is usually the major constituent and the binder portion constitutes a relatively minor amount. Although the sand employed is preferably dry sand, some moisture can be tolerated.This is particularly true if the solvent employed is non-water-miscible or if an excess of the polyisocyanate necessary for curing is employed, since such excess polyisocyanate will react with the water and water is a useful solvent for the amine polyol.

As previously state the excellent shakout or collapsibility of cores made using the binder of this invention is deemed to be a significant discovery. The binders of this invention degrade or break down easily to permit separation of the core from the cast metal. For castings at low temperatures, e.g. 1800"F. or below, shakeout has been a major problem. Generally non-ferrous metals including aluminum and magnesium are cast at these temperatures. Failure of the binder to break down causes great difficulty in removal of the sand from the casting. Thus, cores exhibiting a low degree of shakeout or collapsibility, that is to say a low degree of binder degradation, require more time and energy to remove the sand from the casting.The use of the binder compositions of this invention resu Its in many cases of virtually 100% shakeout without the application of any external energy. The improvement in shakeout is attributable to the presence of the amine polyol in the binder composition. As will be appreciated by those skilled in the art, the ability of any core to shakeout is dependent to an extent upon the amount of binder used to bond the sand particles into a coherent shape.

The percent binder utilized, based on the weight of the sand, depends upon the desired core properties which are requjired from the binder system. As can be appreciated, as the amount of binder in the system increases an increase in the tensile strength of the core generally occurs. Accordingly, the binder level may be varied within reasonable limits to achieve the desired performance properties. A preferred range of binder is, in this invention, from 0.7% to 2.5% based upon the weight of sand. However, it may be possible to use as little as 0.5% and as much as 10% binder and still achieve properties which are of advantage in certain applications. However it has also been noted that when the binder level is increased the degree of shakeout may decrease at the higher binder levels.

The present invention is further illustrated by the following examples in which, unless otherwise indicated, all parts are by weight and all percentages are weight percentage.

EXAMPLE 1 An amine polyol was prepared by propoxylating 1.0 mile of ethylene diamine with 4.2 moles of propylene oxide. A 40% solids solution of the amine polyol was prepared by dissolving the polyol in an aromatic solvent commerically available under the brand name HISOL 10. This solution is referred to as Part 1. A polymeric isocyanate solution, 75% solids, based on Mondur MR, commercially available from Mobay, was prepared using an aromatic solvent, also HISOL 10. The isocyanate solution is referred to as Part II.

Wedron 5010 sand (washed and dried, fine grained silica sand, AFSGFN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Part II was added to the coated sand and blended until a homogeneous sand mix was prepared. A near stoichiometic amount of polyisocyanate, a slight excess, to completely react with the hydroxyl groups of the polyol was used. One an a half percent (12%) of total binder (equal amounts of Part I and II) by weight of sand was used.

The mix of sand, polyol and polyisocyanate was placed in a core box and standard tensile briquettes, known as "dog bones", were prepared. A work time of five and a half minutes and a strip time of eight minutes was achieved. Tensile strengths after two hours, four hours and 24 hours were 300, 371 and 387 psi, respectively.

The "dog bone" cores were used in shakeout studies with aluminum castings. Seven tensile briquettes (dog bones) were arranged in a mold. The mold incorporated a gating system. The mold is designed to provide hollow castings having a metal thickness of approximately one-quarter inch on all sides. An opening at an end of the casting is provided for removal of the core from the casting. Molten aluminum at approximately 1300"F. prepared from aluminum ingots was poured into the mold. After cooling for about an hour the aluminum castings are broken from the gating system and removed from the mold for shakeout testing.

Shakeout tests are performed by placing a casting in a one gallon container. The container is placed on an agitating mechanism and tumbled for two minutes. The weight of the sand core which is removed from the casting in this manner is compared to the initial weight of sand core and a percent shakeout is calculated.

Sand remaining in the casting after the agitation described above is removed by scraping and also weighed.

The sand core, bonded with the amine polyol-polyisocyanate binder described above, collapsed and flowed out of the aluminum casting without using the agitation mechanism and without the application of any external mechanical energy. Shakeout was 100%.

EXAMPLES 2-6 Using the procedures described in Example 1 dog bone test cores were prepared using the components and methods listed and described below. The core were used in shakeout tests using aluminum castings as described in Example 1.

* * Example 2 Example 3 Example 4 Example 5 Example 6 Sand Wedron Wedron Wedron Wedron Wedron Wedron 5010 5010 5010 5010 5010 Amine com- Diethylene Triethylene Ethylene pound Triamine Tetramine Diamine Alkylene Propylene Propylene Propylene Oxide(AO) Oxide Oxide Oxide Mole Ratio 5.1:1 6.2:1 12:1 AO:amine Amine Triethanol- QUADROLb Polyol amine from UPJOHNa Poly- Mondur MR Mondur MR Mondur MR Mondur MR Mondur MR isocyanate Solvent in 40% 10% 60% 60% 60% Amine Polyol HISOL 10 ISOPHORONE ISOPHORONE HISOL 10 HISOL 10 Solvent in NONE NONE 25% 25% 25% Polyisocyanate HISOL 10 HISOL 10 HISOL 10 Catalyst NONE NONE NONE NONE NONE Work Time 5 min. 2 min. 0.5 min. 6 min. 5 min.

Strip Time 12 min. 4.5 min. 1.0 min. 9 min. 8 min.

Percent 1.5% 1.5% 1.5% 1.5% 1.5% Binder 40% Part I 50% Part I 60% Part I 50% Part I 50% Part I 60% Part II 50% Part II 40% Part II 50% Part II 50% Part II Tensile Strength in psi 2 hr. 100 153 85 360 339 4 hr. 118 210 113 365 350 24 hr. 163 247 - 230 383 Shakeout 100% 100% 100% 100% 100% Cores made as described above were observed to collapse and flow out of the casting without using an agitation mechanism and without the application of any external mechanical energy.

aUPJOHN is a brand oftriethanolamine, i.e. ethoxylated ammonia, commercially available from Upjohn Corp.

bQUADROL is the brand of propoxylated ethylene diamine, mole ratio of 4:1, commercially available from BASF Wyandotte.

EXAMPLE 7 An aromatic amine polyol was prepared by propoxylating one mole of meta-phenylenediamine with 4.2 moles of prnpylene. oxide. A 40% solids solution of the aromatic amine polyol was prepared by dissolving the polyol in an aliphatic solvent, butyl Cellosolve. This solution is referred to as Part I. A polymeric isocyanate solution, 75% solids, based on Mondur MR, commercially available from Mobay, was prepared using an aromatic solvent, commercially available as HISOLs 10. The isocyanate solution is referred to as Part II. A nearly stoichiometric amount of polyisocyanate to completely react with the hydroxyl groups of the polyol was used.

Wedron 5010 sand (washed and dried, fine grained silica sand, AFSGFN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Incorporated in Part I was a uretha catalyst, triethylenediamine, commercially available under the brand name DABCO. This catalyst is a well known urethane catalyst. Based on the weight of Part I 0.8% catalyst was used. Part II was added to the coated sand and blended until a homogeneous sand mix was prepared. One and a half percent (it%) oftotal binder (Part land Part II) by weight ofsandwas used.

The mix of sand, polyol, catalyst and polyisocyanate was placed in a core box and standard tensile briquettes, known as "dog bones", were prepared. A work time of seventy minutes and a strip time of one hundred ten minutes was achieved. Tensile strength after 24 hours was 230 psi.

The "dog bone" cores were used in shakeout studies with aluminum castings. Seven tensile briquettes (dog bones) were arranged in a mold. The mold incorporated a gating system. The mold is designed to provide hollow castings having a metal thickness of one-quarter inch on all sides. An opening at an end of the casting is provided for removal of the core from the casting, Molten aluminum at approximately 1300"F.

prepared from aluminum ingots was poured into the mold. After cooling for about an hour the aluminum castings were broken from the gating system and removed from the mold for shakeout testing.

Shakeout tests are performed by placing a casting in a one-gallon container. The container is placed on an.

agitating mechanism and tumbled for two minutes. The weight of the sand core which is removed from the casting in this manner is compared to the initial weight of sand core and a percent shakeout is calculated.

The sand core, bonded with the amine polyol, polyisocyanate binder described above, collapsed and flowed out of the aluminum casting without using the agitation mechanism and without the application of any external mechanical energy. Shakeout was 100%.

EXAMPLE 8-11 Using the procedures described in Example 7 dog bone test cores were prepared using the components and methods as described below. The cores were used in shakeout tests using aluminum castings as described in Example 7.

Example 8 Example 9 Example 10 Example 11 Sand Wedron Wedron Wedron Wedron 5010 5010 5010 5010 Amine Component Alkylene Oxide Mole Ratio AO:amine Amine Polyol PluracolC Pluracolc Pluracold Pluracold 767 767 795 795 Poly- Mondur MR Mondur MR Mondur MR Mondur MR isocyanate Solvent in 40% 35% 35% 35% Amine Polyol HISOL 10 Water HISOL 10 HISOL 10 Solvent in 44% None 35% 35% Polyisocyanate Catalyst (1)1.4% None None (1) 121% WorkTime 25min. lOmin. 11.5min. 7min.

Strip Time 31 min. 16min. 16min. 10.5min.

Percent 1.5% 1.7% 1.5% 1.5% Binder 50% Part I 60% Part I 50% Part 1 50% Part I 50% Part II 40% Part II 50% Part II 50% Part II Tensile Strength in psi 2 hr. 225 108 203 223 (3 hrs.) 4 hr. -- 128 (3 hr.) 213 210 24 hr. 368 -- 323 320 Shakeout 92% 100% 100% Cores made as described above were observed to collapse and flow out of the casting without using an agitation mechanism and without the application of any external mechanical energy.

(1) 50% phenylpropyl pyridine and 50% of a lithium salt of a carboxylic acid.

c Pluracol 767 is a brand name for a propoxylated aromatic amine-based polyol commercially available from BASF Wyandotte.

dPluracol 795 is a brand name for an ethoxylated aromatic amine-based polyol commercially available from BASFWyandotte.

ea blend of HISOL 10 and kerosene.

EXAMPLE 12 An aromatic amine polyol was prepared by propoxylating one mole of ortho-phenylenediamine with 4.2 moles of propylene oxide. A 40% solids solution of the aromatic amine polyol was prepared by dissolving the polyol in isophorone. This solution is referred to as Part I. A polymeric isocyanate, Mondur MR, is referred to as Part II. A nearly stoichiometric amount of polyisocyanate to completely react with the hydroxyl groups of the polyol was used.

Wedron 5010 sand (washed and dried, fine grained silica sand, AFSGFN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Incorporated in Part I was a 33% solution in dipropylene glycol of a urethane catalyst, triethylenediamine, commercially available under the brand name DABCO. This catalyst is a well-known urethane catalyst. Based on the weight of Part 1, 1.0% catalyst was used.Part II was added to the coated sand and blended until a homogeneous sand mix was prepared. One and a half percent (1-%) of total binder (55% Part I and 45% Part II) by weight of sand was used.

The mix of sand, polyol, catalyst and polyisocyanate was placed in a core box and standard tensile briquettes, known as "dog bones", were prepared. A work time of nine minutes and a strip time of twenty minutes was achieved. Tensile strength in psi after 2 hours and 24 hours were 292 and 313, respectively.

The "dog bone" cores were used in shakeout studies with aluminum castings. Seven tensile briquettes (dog bones) were arranged in a mold. The mold incorporated a gating system. The mold is designed to provide hollow castings having a metal thickness of one-quarter inch on all sides. An opening at an end of the casting is provided for removal of the core from the casting. Molten aluminum at approximately 1300"F prepared from aluminum ingots was poured into the mold. After cooling for about an hour the aluminum castings were broken from the gating system and removed from the mold for shakeout testing.

Shakeout tests are performed by placing a casting in a one-gallon container. The container is placed on an agitating mechanism and tumbled for two minutes. The weight of the sand core which is removed from the casting in this manner is compared to the initial weight of sand core and a percent shakeout is calculated.

The sand core, bonded with the amine polyol-polyisocyanate-catalyst binder described above, collapsed and flowed out of the aluminum casting without using the agitation mechanism and without the application of any external mechanical energy. Shakeout was 100% EXAMPLES 13-15 Using the procedures described in Example 12 dog bone test cores were prepared using the components and methods as described below.The cores were used in shakeout tests using aluminum castings as described in Example 12 Example 13 Example 14 Example 15 Sand Wedron Wedron Wedron 5010 5010 5010 Amine Meta phenylene CURITHANE103, Anile Component diamine an anile formalde hyde resin from Upjohn Alkylene Propylene oxide Propylene oxide Propylene oxide Oxide Mole Ratio AO:amine 4.2:1 4.2:1 2.2:1 Amine Polyol Polyisocyanate Mondur MR Mondur MR Mondur MR Solvent in 60% Isophorone 60% Isophorone 60% (X) Amine Polyol Solvent in None None None Polyisocyanate Catalyst None None 1%Dabco WorkTime 45 min. 70 min. 70 min.

Strip Time 78min. 101 min. 140min.

Percent 1.5% 1.5% 1.5% Binder 55% Part I 73% Part I 61%PartI 45% Part II 27% Part II 39% Part II Tensile Strength in psi: 2 hr. 145 23 4 hr. 307 24hr. 320 140 180 Shakeout 89% 100% 74% (X) a blend of butyl cellosolve acetate (40%) and HISOL 10 (20%) Cores made as described above were observed to collapse and flow out of the casting using an agitation mechanism, with the application of external mechanical energy.

EXAMPLE I An amine polyol was prepared by propoxylating 1.0 mole of meta-phenylene diamine with 6.0 moles of propylene oxide. A 40% solids solution of the amine amine polyol was prepared by dissolving the polyol in blend of solvent 40% isophorone, 16.5% of an aromatic solvent art 3.5% kerosene. This solution is referred to as Part I. A polymeric isocyanate solution, 75% solids, based on Mondur MR, commercially available from Mobay, was prepared using an aromatic solvent, HISOL10. The isocyanate solution is referred to as Part II.

A near stoichiometic amount of polyisocyanate to completely react with the hydroxyl groups of the poiyol was used.

Wedron 5010 sand (washed and dryed fine grained silica sand, AFSGFN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Part II was added to the coated sand and blended until a homogenous sand mix was prepared. One and half percent (1 1/2%) of total binder (Equal amounts of Part I and Part II) by weight of sand was used.

The mix of sand, polyol and polyisocyanate was blown into a conventional core cavity or box for making standard tensile briquettes test cores known as "dog bones". The dog bone test cores were cured by exposing the cores to a tertiary amine catalyst. The amine catalyst, dimethylethylamine, was suspended in carbon dioxide, an inert carrier gas. The cores were exposed to the amine catalyst for approximately 20 seconds (gas time) and allowed to remain in the core box for 10 minutes (dwell time) before removing the core from the box. Tensile strengths in psi were 25 out of the box, 72 after one hour, and 135 after 24 hours.

The "dog bone" cores were used in shakeout studies with aluminum castings. Seven tensile briquettes (dog bones) were arranged in a mold. The mold incorporated a gating system. The mold is designed to provide hollow castings having a metal thickness of approximately one-quarter inch on all sides. An opening at an end of the casting is provided for removal of the core from the casting. Molten aluminum at approximately 1300 F. prepared from aluminum ingots was poured into the mold. After cooling for about an hour the aluminum castings are broken from the gating system and removed from the mold for shakeout testing.

Shakeout tests are performed by placing a casting in a one gallon container. The container is placed on an agitating mechanism and tumbled for two minutes. The weight of the sand core which is removed from the casting in this manner is compared to the initial weight of sand core and percent shakeout is calculated. Sand remaining in the casting after the agitation described above is removed by scraping and also weighed. The sand core, bonded with the amine polyol, polyisocyanate binder described above, collapsed and flowed out of the aluminum casting without using the agitation mechanism and without the application of any external mechanical energy. Shakeout was 100% EXAMPLES 2-6 Using the procedures described in Example I test cores were prepared and tested using components methods listed and described below.

Example 2 Example 3 Example 4 Example 5 Example 6 Sand Wedron 5010 Wedron 5010 Wedron 5010 Wedron 5010 Wedron 5010 Amine Aniline Ortho-pheny- Meta-pheny- Meta-pheny- CURITHANE Compound lene lene lene dia- 103, a mine aniline formalde hyde resin available from Upjohn Alkylene Propylene Propylene Propylene Propylene Propylene Oxide Oxide Oxide Oxide Oxide Oxide Mole Ratio AO:Amine 2:1 4.2:1 4.2:1 8:1 4::1 Amine Polyol Polyisocyanate Mondur MR Mondur MR Mondur MR Mondur MR Mondur MR Solvent in Amine Polyol 60% (1) 60% Isophorone 60% Isophorone 60% (1) 60% Isophorone Solvent in Polyisocyanate NONE 25% (2) 25% HISOL 10 25% (2) NONE Catalyst Trimethyl Do methyl Dimethyl- Dimethyl- Trimethyl amine ethylamine ethylamine ethylamine amine suspended suspended suspended in CO2 IN CO2 in CO2 Gas Time 10 sec. 10 sec. 10 sec. 20 sec. 5 sec.

Dwell Time 5 min. 3 min. 10 min. 10 min. 2 min.

Tensile Strength psi Out of the Box 30 50 5 105 30 lhr. 100 65 105 24 hr. 90 85 113 50 Total Binder 1.5% 1.5% 1.5% 1.5% 1.5% Part 175% Part 150% Part 150% Part 150% Part 175% Part II 25% Part II 50% Part II 50% Part II 50% Part II 25% Shakeout 100% 100% 100% 100% 100% Cores made as described above were observed to collapse and flow out of the casting without using an agitation mechanism and without the application of any external mechanical energy.

(1) a blend of isophorone (40%), aromatic solvents (16.5%), Kerosene (3.5%) (2) a blend of an aromatic solvent commercially available as Texaco Solvent 7545 (19%) and Kerosene (6%) EXAMPLE 7 An amine polyol was prepared by propoxylating 1.0 mole of metaphenylene diamine with 8.0 moles of propylene oxide. A phenolic polyol, commercially available as PEPB resin was added to the amine polyol to make a polyol blend. The ratio o- amine polyol to non-amine polyol was 2:1. A 60% solid solution of the polyol blend was prepared by dissolving the polyol blend in isophorone solvent. This solution is referred to as Part I.A polymeric isocyanate solution, 75% solids, based on Mondur MR, commercially available from Mobay, was prepared using a solvent blend consisting of 19% of Texaco 7545, an aromatic solvent, and 6% kerosene. The isocyanate solution is referred to as Part II. A near stoichiometric amount of polyisocyanate to completely react with the hydroxyl groups of the polyol was used.

Wedron 5010 sand (washed and ryed fine grained sand, AFSGN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Part II was added to the coated sand and blended until a homogeneous sand mix was prepared. One and a half percent (11/2%) of total binder (44% of Part I and 56% of Part II) by weight of sand was used.

The mix of sand, polyol and polyisocyanate was blown into a conventional core cavity or box for making standard tensile briquette test cores known as "dog bones". The dog bone test cores were cured by exposing the cores to a tertiary amine catalyst. The amine catalyst, dimethylethylamine was suspended in carbon dioxide, an inert carrier gas. The cores were exposed to the amine catalyst for approximately 5 seconds (gas time) and allowed to remain in the core box for one minute (dwell time) before removing the core from the box. Tensile strengths in psi were 58 immediately from the box, 200 after one hour, and 210 at the time of casting.

EXAMPLES 8 AND 9 Sand Wedron 5010 Wedron 5010 Amine Compound Curithane 103 Alkylene Oxide Propylene Oxide Mole Ratio Alkylene Oxide:Amine Amine Polyol Pluracol 7351 Nonamine Polyol Phenolic polyol Phenolic polyol Ratio Amine Polyol:Nonamine Polyol 2:1 2:1 Polyisocyanate Mondur MR Solvent in Polyol Blend 40% Butyl Cellosolve 40% Butyl Cellosolve Acetate Acetate Solvent in Polyisocyanate 25% Aromatic solvent 25% kerosene 7545, 6% kerosene Catalyst Trimethylamine Trimethylamine Gas Time 5 sec. 5 sec.

Dwell Time 1 min. 1 min.

Tensile Strength in psi 45 52 127(1 hr.) 125(1 hr) 110 (4 hrs.) 162 (time of pouring) 127 (time of pouring) Total Binder 11/2% 11/2% Part 144% Part 150% Part 1156% Part 1150% Shake Out 100% 48% aAn amine based polyol from BASF (believed to be ethoxylated and aromatic).

The sand core bond with the amine polyol derived from propoxylating Curithane 103, an aniline formaldehyde resin available from Upjohn, collapsed and flowed out of the aluminum casting without using the agitation mechanism and without the application of external energy. The sand core based on Pluraco 735 was tumbled to obtain the indicated degree of shakeout.

EXAMPLE 10 An amine polyol was prepared by propoxylating 1.0 mole of ethylene diamine with 8.0 moles of propylene oxide, A 50% solids solution of the amine polyol was prepared by dissolving the polyol in blend of solvent 30% isophorone, 16.5% of an aromatic solvent art 3.5% kerosene. This solution is referred to as Part I. A polymeric isocyanate solution, 75% solids, based on Mondur MR, commercially available from Mobay, was prepared using an aromatic solvent, Texaco 7545 (19%) and Kerosene (6%). The isocyanate solution is referred to as Part II. A near stoichiometic amount of polyisocyanate to completely react with the hydroxyl groups of the polyol was used.

Wedron 5010 sand (washed and dryed fine grained silica sand, AFSGFN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Part II was added to the coated sand and blended until a homogenous sand mix was prepared. One and a half percent (1 1/2%) of total binder (Equal amounts of Part I and Part II) by weight of sand was used.

The mix of sand, polyol and polyisocyanate was blown into a conventional core cavity or box for making standard tensile briquettes test cores known as "dog bones". The dog bone test cores were cured by exposing the cores to a tertiary amine catalyst, trimethyl amine. The cores were exposed to the amine catalyst for approximately 10 seconds (gas time) and allowed to remain in the core box for 5 minutes (dwell time) before removing the core from the box. Tensile strengths in psi were 80, 15 minutes after gassing, and 135 after 24 hours.

The "dog bones" cores were used in shakeout studies with aluminum castings. Seven tensile briquettes (dog bones) were arranged in a mold. The mold incorporated a gating system. The mold is designed to provide hollow castings having a metal thickness of approximately one-quarter inch on all sides. An opening at an end of the casting is provided for removal of the core from the casting. Molten aluminum at approximately 13000F. prepared from aluminum ingots was poured into the mold. After cooling for about an hour the aluminum castings are broken from the gating system and removed from the mold for shakeout testing.

EXAMPLE II A 58.5% solid solution of phenolic polyol, commercially available as PEP resin was prepared by dissolving the polyol in HISOL 10. This solution is referred to as Part I. A polymeric isocyanate solution, 75% solids, based on Mondur MR. commecially available from Mobay, was prepared using a solvent blend consisting of 19% of Texaco 7545, an aromatic solvent, and 6% kerosene. The isocyanate solution is referred to as Part II. A near stoichiometric amount of polyisocyanate to completely react with the hydroxyl groups of the polyol was used.

Wedron 5010 sand (washed and dryed fine grained sand, AFSGEN 66) was placed in a suitable mixing apparatus. Part I was admixed with the sand until a uniform coating was provided. Part II was added to the coated sand and blended until a homogeneous sand mix was prepared. One and eight tenths percent (1.8%) of total binder (Equal amounts of Part I and of Part II) by weight of sand was used.

The mix of sand, polyol and polyisocyanate was blown into a conventional core cavity or box for making standard tensile briquette test cores known as "dog bones". The dog bone test cores were cured by exposing the cores to a tertiary amine catalyst. The amine catalyst, dimethyl ethyl amine, was suspended in carbon dioxide, an inert carrier gas. The cores were exposed to the amine catalyst for approximately 1 second (gas time) and taken immediately out of the core box. Tensile strengths in psi were 182 immediately (1 min) from the box, 225 after four hours, and 297 after twenty.

The sand core, bonded with the phenolic resin, polyisocyanate binder described above, failed to shakeout after agitation. Shakeout was Q%. A comparison of this Example with previous Examples reveals the advantages secured in the area of shakeout using an amine polyol in a cold box system in relation to other polyols used in a cold box system when low temperatures casting is made.

Claims

1. A binder composition useful for making shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising in admixture a polyol component, a liquid polyisocyanate component and a curing agent, said polyol component comprising an aromatic amine polyol and said curing agent comprising a tertiary amine which is gaseous at room temperature.

2. The binder composition of Claim 1 wherein the aromatic amine polyol is the reaction product of an aromatic amine compound and an alkylene oxide.

3. The binder composition of Claim 2 wherein the aromatic amine compound comprises aniline.

4. The binder composition of Claim 2 wherein the aromatic amine compound comprises an aniline formaldehyde adduct.

5. The binder composition of Claim 2 wherein the alkylene oxide comprises propylene oxide.

6. The binder composition of Claim 2 wherein the alkylene oxide comprises ethylene oxide.

7. The binder composition of Claim 2 wherein the amine polyol component comprises a water solution.

8. The binder composition of Claim 2 wherein the amine polyol component comprises a solution of an organic solvent.

9. The binder composition of Claim 8 wherein the organic solvent comprises an aromatic organic solvent.

10. A binder composition useful for making shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising in admixture a polyol component, a liquid polyisocyanate component and a curing agent said polyol component comprising an adduct of ammonia and an alkylene oxide and said curing agent comprising a tertiary amine which is gaseous at room temperature.

11. The binder composition of Claim 10 wherein thbe polyol component comprises a water solution.

12. Process of forming shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising: a) Forming a foundry mix by distributing on an aggregate a binding amount of up to 10%, based upon the weight of the aggregate, of a binder composition, said composition comprising in admixutre a polyol component, a liquid polyisocyanate component, said polyol component comprising an amine polyol.

b) Shaping the foundry mix into a desired foundry article; and c) Contacting the shaped foundry mix with a tertiary amine which is gaseous at room temperature until the binder has cured.

13. The process of Claim 12 wherein the amine polyol component is the reaction product of an aromatic amine compound and an alkylene oxide.

14. The process of Claim 13 wherein the alkylene oxide comprises propylene oxide.

15. The process of Claim 13 wherein the alkylene oxide comprises ethylene oxide.

16. The process of Claim 13 wherein the amine polyol component comprises a water solution.

17. The process of Claim 13 wherein the aromatic amine compound comprises aniline.

18. The process of Claim 13 wherein the aromatic amine compound comprises an aniline formaldehyde adduct.

19. The process of Claim 13 wherein the amine polyol component comprises a solution of an organic solvent.

20. The process of Claim 13 wherein the amine polyol component comprises a solution of an aromatic organic solvent.

21. The process of Claim 12 wherein the amine polyol component is the reaction product of an aliphatic amine compound and an alkylene oxide.

22. The process of Claim 21 wherein the alkylene oxide comprises propylene oxide.

23. The process of Claim 21 wherein the alkylene oxide comprises ethylene oxide.

24. The process of Claim 21 wherein the amine polyol component comprises a water solution.

25. The process of Claim 21 wherein the aliphatic amine compound comprises ethylene diamine.

26. The process of Claim 21 wherein the amine polyol component comprises a solution of an organic solvent.

27. The process of Claim 21 wherein the amine polyol component comprises a solution of an aromatic organic solvent.

28. The process of Claim 21 wherein the amine polyol comprises an admixture of an aliphatic amine polyol and an aromatic amine polyol.

29. The process of claim 21 wherein the polyol component comprises an amine polyol and a non-amine polyol.

30. The process of Claim 29 wherein the non-amine polyol comprises a phenolic resin having the general formula.

wherein R is hydrogen or a phenolic substituent meta to the hydroxyl group of the phenol, m and n are numbers the sum of which is at least 2, and the ratio of m-to-hydrogen being at least 1.

31. Process of casting lightweight metal articles, said metal articles being shaped by use of foundry articles, which foundry articles collapse after casting said metal articles comprising: a) Forming a foundry article as described in Claim 12; b) Heating said lightweight metal until it melts and is castable; c) Casting said lightweight metal using the shaped foundry article; d) Allowing the cast metal to solidify; and e) Collapsing the foundry article and removing said collapsed Foundry Article from the cast lightweight metal article.

32. A binder composition useful for making shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising in admixutre a polyol component and a liquid polyisocyanate component, said polyol component comprising an aromatic amine polyol.

33. The binder composition of Claim 11 wherein the aromatic amine polyol is the reaction product of an aromatic amine compound and an alkylene oxide.

34. The binder composition of Claim 12 wherein the aromatic amine compound comprises aniline.

35. The binder composition of Claim 12 wherein the aromatic amine compound comprises an aniline formaldehyde adduct.

36. The binder composition of Claim 12 wherein the alkylene oxide comprises propylene oxide.

37. The binder composition of Claim 12 wherein the alkylene oxide comprises ethylene oxide.

38. The binder composition of Claim 12 wherein the amine poloyl component comprises a water solution.

39. The binder composition of Claim 12 wherein the amine polyol component comprises a solution of an organic solvent.

40. The binder composition of Claim 12 wherein the organic solvent comprises an aromatic organic solvent.

41. The binder composition of Claim 12 containing a curing catalyst, said catalyst comprising a liquid or solid urethane catalyst.

42. A binder composition useful for making shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising in admixture a polyol component and a liquid polyisocyanate component, said polyol component comprising an adduct of ammonia and an alkylene oxide.

43. The binder composition of Claim 21 wherein the polyol component comprises a water solution.

44. The binder composition of Claim 21 wherein the binder composition contains a curing catalyst, said catalyst comprising a liquid or solid urethane catalyst.

45. Process of forming shaped foundry articles for use in casting lightweight metals, which articles collapse after casting of said lightweight metals, comprising: a) Forming a foundry mix by distributing on an aggregate a binding amount of up to 10%, based upon the weight of the aggregate, of a binder composition, said composition comprising in admixutre a polyol component and a liquid polyisocyanate component, said polyol component comprising an amine polyol.

b) Shaping the foundry mix into a desired foundry article; and c) Allowing the article to cure.

46. The process of Claim 24 wherein the amine polyol component is the reaction product of an aromatic amine compound and an alkylene oxide.

47. The process of Claim 25 wherein the alkylene oxide comprises propylene oxide.

48. The process of Claim 25 wherein the alkylene oxide comprises ethylene oxide.

49. The process of Claim 25 wherein the amine polyol component comprises a water solution.

50. The process of Claim 25 wherein the binder composition contains a curing catalyst, said catalyst comprising a liquid or solid urethane catalyst.

51. The process of Claim 25 wherein the aromatic amine compound comprises aniline.

52. The process of Claim 25 wherein the aromatic amine compound comprises an aniline formaldehyde adduct.

53. The process of Claim 25 wherein the amine polyol component comprises a solution of an organic solvent.

54. The process of Claim 25 wherein the amine polyol component comprises a solution of an aromatic organic solvent.

55. The process of Claim 24 wherein the amine polyol component is the reaction product of an aliphatic amine compound and an alkylene oxide.

56. The process of Claim 34 wherein the alkylene oxide comprises propylene oxide.

57. The process of Claim 34 wherein the alkylene oxide comprises ethylene oxide.

58. The process of Claim 34 wherein the amine polyol component comprises a water solution.

59. The process of Claim 34 wherein the binder composition contains a curing catalyst, said catalyst comprising a liquid or solid urethane catalyst.

60. The process of Claim 34 wherein the aliphatic amine compound comprises ethylene diamine.

61. The process of Claim 34 wherein the amine polyol component comprises a solution of an organic solvent.

62. The process of Claim 34 wherein the amine polyol component comprises a solution of an aromatic organic solvent.

63. The process of Claim 34 wherein the amine polyol comprises an admixutre of an aliphatic amine polyol and an aromatic amine polyol.

64. Process of casting lightweight metal articles, said metal articles being shaped by use of foundry articles, which foundry articles collapse after casting said metal articles comprising: a) Forming a foundry article as described in Claim 34; b) Heating said lightweight metal until it melts and is castable; c) Casting said lightweight metal using the shaped foundry article; d) Allowing the cast metal to solidify; and e) Collapsing the foundry article and removing said collapsed Foundry Article from the cast lightweight metal article.