Patent Application
20110129387
In the foundry industry, one of the procedures used for making metal parts is “sand casting”. In sand casting, disposable foundry shapes, e.g. molds, cores, sleeves, pouring cups, coverings, etc. are fabricated with a foundry mix that comprises a mixture of a refractory (typically sand) and an organic or inorganic binder.
Foundry shapes are typically made by the so-called no-bake, cold-box processes, and/or heat cured processes. In the no-bake process, a liquid curing catalyst is mixed with a refractory and binder to form a foundry mix before shaping the mixture in a pattern. The foundry sand mix is shaped by compacting it in a pattern, and allowing it to cure until it is self-supporting. In the cold-box process, a vaporous curing catalyst is passed through a shaped mixture (usually in a corebox) of the aggregate and binder to form a cured foundry shape. In the heat cured processes the shape mixture is exposed to heat which activates the curing catalyst to form the cured foundry shape.
There are many requirements for a binder system to work effectively. For instance, the binder typically has a low viscosity, must be gel-free, and remain stable under storage and use conditions. In order to obtain high productivity in the manufacturing of foundry shapes, binders are needed that cure efficiently, so the foundry shapes become self-supporting and handleable as soon as possible.
With respect to the no-bake and heat cured processes, there must be adequate worktime to allow for the fabrication of larger cores and molds. On the other hand, with respect to cold-box processes, the shaped foundry mix must cure nearly instantaneously upon contact with the vaporous curing catalyst. The foundry shapes made with the foundry mixes using either no-bake, cold-box or heat cured binders have adequate mechanical strengths, particularly immediate tensile and transverse strengths, scratch hardness, and exhibit resistance to ambient humidity.
One of the greatest challenges facing the formulator is to formulate a binder that will hold the foundry shape together after is made so it can be handled, stored and will not disintegrate prematurely during the metal casting process, yet will allow for acceptable mold and core removal properties upon cooling of the solidified cast metal part, often referred to as shake-out. Without this property, time consuming and labor intensive means must be applied to break down the spent foundry shapes so the metal part can be removed from the casting mold and core assembly. Another related property required for an effective foundry binder is that foundry shapes made with the binder must release readily from the pattern in which they are created.
The flowability of a foundry mix made from a refractory and an organic binder can pose greater problems with respect to cold-box applications. This is because, in some cases, the components of the binder, particularly the components of phenolic urethane binders, may prematurely react after mixing with the refractory sand, while they are waiting to be used. If this premature reaction occurs, it will reduce the flowability of the foundry mix and the molds and cores made from the binder will have reduced mechanical strengths. This reduced flowability and decrease in strength with time indicates that the “benchlife” of the foundry mix is inadequate. If a binder results in a foundry mix without adequate benchlife, the binder is of limited commercial value.
In view of all these requirements for a commercially successful foundry binder, the pace of development in foundry binder technology is gradual. It is not easy to develop a binder that will satisfy all of the requirements of interest in a cost-effective way.
Furthermore, besides excellent performance and cost effectiveness, demands for the composition of the formulation may exist because of environmental, health, and safety regulations and concerns. Environmental concerns are particularly relevant today because most of the foundry binders used commercially contain significant amounts of aromatic hydrocarbon solvents, which in turn may comprise compounds like benzene, toluene, xylene, 1,2,4-trimethylbenzene, naphthalene and other aromatic compounds and fractions of concern. Recently, there has been increased concern with using aromatic hydrocarbon solvents in foundry binders and an interest in reducing the amount used or totally eliminating their use prevails.
The prior art discloses that the reduction and possible elimination of aromatic hydrocarbon solvents in foundry binder systems based upon phenolic resole resins and polyisocyanates has been explored several times. For instance, European Patent No. 0771569 describes replacing aromatic hydrocarbon solvents with methyl esters of one or more fatty acids, with a carbon chain from 12 carbon atoms. Although the binders make useful cores and molds, it has been found that smoke and acrid odors result during the pouring, cooling and shakeout process, and that it is more difficult to reclaim and reuse sand obtained from spent molds and cores made with these binders. Consequently, in practice, there is a tendency to use the fatty acid esters as a co-solvent in combination with traditional aromatic hydrocarbon solvents.
More recently European patent 1057554 disclosed the use of alkyl silicates, in particular, tetraethyl silicate, to replace aromatic hydrocarbon solvents. This technology also has some drawbacks, e.g. gel formation in the acidic scrubber solution used for abating the amine curing gas and the formation of fine white silica particles which may deposit on the cast part, accumulate in the spent sand or become airborne.
Acyclic aliphatic solvents, for instance kerosene and tetradecene have been used in small additions in polyol-polyisocyanate binders, particularly phenolic urethane cold-box and no-bake binders, but their strong non-polar solvency properties have resulted in significantly limiting their amount in the binder formulation to less than five weight percent in the total binder, i.e. the combined weight of the Part I (polyol component) and the Part II (polyisocyanate component).
In view of this background, there is a need to develop foundry binders that contain no aromatic hydrocarbon solvents or employ them at a much reduced level, while maintaining excellent performance and cost effectiveness and adequate consideration for environmental, health and safety concerns.
This disclosure relates to foundry binders comprising (a) a polyol component selected from the group consisting of phenolic resins, polyether polyols, polyester polyols, aminopolyols, and mixtures thereof, and (b) a polyisocyanate component, wherein component (a) and/or (b) further comprise, as a solvent, one or more cycloalkanes. The disclosure also relates to foundry mixes prepared with the foundry binders, the cold-box, no-bake and heat cured processes for making foundry shapes using the foundry mixes, and processes for making cast metal parts using the foundry shapes and the processes for metal casting.
There are environmental, health, and safety advantages of using the binders according to the present invention because aromatic hydrocarbon solvents comprising benzene, toluene, xylene, 1,2,4-trimethylbenzene, naphthalene and other aromatic compounds and fractions can be eliminated or reduced when formulating the foundry binders. As result, unwanted gases, fumes and odors are reduced or eliminated when foundry shapes are made from foundry mixes made with the binders according to the present invention and when metal parts are cast using these foundry shapes. Furthermore, there is no potential exposure to silica particles that exists when alkyl silicates are used as solvents in foundry binders used for making foundry shapes.
It is believed that the use of cycloalkanes as solvents in the defined foundry binders, as a complete or partial replacement for aromatic hydrocarbon solvents may: (1) reduce the amount of photochemically active species that may have a deleterious effect on the ozone layer and which are liberated when foundry shapes are made with the binders and when the foundry shapes are used to make metal parts in the course of the metal casting process; (2) reduce the formation of tar-like materials in the venting system of semi-permanent molds, a technology commonly used to make automotive cylinder heads; (3) provide improvements in quality of the cast metal parts made from the foundry shapes; (4) improve mold and core quality by eliminating or reducing solvent build-up in attrition reclaimed sand and green sand molding systems; and (5) reduce dense smoke formation during pouring, cooling and shake-out.
Because it is known that binders based upon polyols and polyisocyanates, particularly phenolic resole resins, are sensitive to the various properties of the solvents, it was unexpectedly found that cycloalkanes could be used to completely or partially replace aromatic hydrocarbon solvents that are traditionally used in such binders without adversely affecting the performance characteristics of the binder with respect to product storage stability and core and mold making performance. This was particularly unexpected because it is known that acyclic aliphatic solvents such as kerosene and tetradecene are not compatible with phenolic resins and polyisocyanates at high levels, especially at a level which would totally replace all aromatic hydrocarbon solvents in the foundry binder.
It is preferred to package and use the binders system as a two-part system.
The polyol component of the foundry binder (Part I) comprises a polyol selected from the group consisting of phenolic resins, polyether polyols, polyester polyols, amine polyols, and mixtures thereof. Preferably used as the polyol are phenolic resole resins.
The polyisocyanate component of the binder (Part II) comprises a polyisocyanate selected from the group consisting of aliphatic polyisocyanates and aromatic polyisocyanates and mixtures thereof. Preferably used as the polyisocyanate because of its availability is methylene diphenylisocyanate.
As was mentioned previously, the preferred polyol is a phenolic resin, which is liquid or organic solvent-soluble. The phenolic resin component of the binder composition is generally employed as a solution in an organic solvent. The amount of solvent used should be sufficient to result in a binder composition with adequate viscosity permitting uniform coating thereof on the aggregate and uniform reaction with the polyisocyanate component in the foundry sand mix. The specific solvent concentration for the phenolic resin will vary depending on the type of phenolic resin employed and its molecular weight. In general, the solvent concentration will be in the range of up to 80% by weight of the polyol component, typically in the range of 20% to 80% by weight of the polyol component.
A phenolic resole resin is preferably prepared by reacting a molar excess of aldehyde with a phenol in the presence of either an alkaline catalyst or a metal catalyst. The phenolic resins are preferably substantially free of water and are organic solvent soluble. The preferred phenolic resins used in the subject binder compositions are well known in the art, and are specifically described in U.S. Pat. No. 3,485,797, which is hereby incorporated by reference. These resins, known as benzylic ether phenolic resole resins, are the reaction products of an aldehyde with a phenol. They contain a preponderance of bridges joining the phenolic nuclei of the polymer, which are ortho-ortho benzylic ether bridges. They are prepared by reacting an aldehyde and a phenol in a mole ratio of aldehyde to phenol of at least 1:1 in the presence of a metal ion catalyst, preferably a divalent metal ion such as zinc, lead, manganese, copper, tin, magnesium, cobalt, calcium, and barium.
The phenol used to prepare the phenolic resole resins include phenol itself and/or any one or more of the phenols which have heretofore been employed in the formation of phenolic resins and which are not substituted at either the two ortho-positions or at one ortho-position and the para-position. Such unsubstituted positions are necessary for the polymerization reaction. Any one, all, or none of the remaining carbon atoms of the phenol ring can be substituted. The nature of the substituent can vary widely and it is only necessary that the substituent not interfere in the polymerization of the aldehyde with the phenol at the ortho-position and/or para-position. Substituted phenols employed in the formation of the phenolic resins include alkyl-substituted phenols, aryl-substituted phenols, cycloalkyl-substituted phenols, aryloxy-substituted phenols, and halogen-substituted phenols, the foregoing substituents containing from 1 to 26 carbon atoms and preferably from 1 to 12 carbon atoms.
Alternatively, novolak resins may be used. Bisphenol F is the simplest novolak and is prepared by reacting a large molar excess of phenol with formaldehyde under acidic conditions, which results in an isomer mixture comprising o,p′ isomers, p,p′ isomers and o,o′ isomers. A typical acid catalyst is oxalic acid.
Specific examples of suitable phenols include phenol, o-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 2,3,4-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-methyl-4-methoxy phenol, and p-phenoxy phenol. Multiple ring phenols such as 4,4′-diphenol and bisphenol A are also suitable.
The aldehyde used to react with the phenol has the formula RCHO wherein R is a hydrogen or a hydrocarbon radical of 1 to 8 carbon atoms. The aldehydes reacted with the phenol can include any of the aldehydes heretofore employed in the formation of phenolic resins such as formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, benzaldehyde and the like, and mixtures thereof. The most preferred aldehyde is formaldehyde.
Polyether polyols are commercially available and their method of preparation and determining their hydroxyl value is well known. The polyether polyols are prepared by reacting an alkylene oxide with a polyhydric alcohol in the presence of an appropriate catalyst such as sodium methoxide according to methods well known in the art. Any suitable alkylene oxide or mixtures of alkylene oxides may be reacted with the polyhydric alcohol to prepare the polyether polyols. The alkylene oxides used to prepare the polyether polyols typically have from two to six carbon atoms. Representative examples include ethylene oxide, propylene oxide, butylene oxide, amylone oxide, styrene oxide, or mixtures thereof. The polyhydric alcohols typically used to prepare the polyether polyols generally have a hydroxy functionality greater than 2.0, preferably from 2.5 to 5.0, most preferably from 2.5 to 4.5. Examples include ethylene glycol, diethylene glycol, propylene glycol, trimethylol propane, glycerine, and tetramethylol methane.
Aminopolyols are also well known and are described in U.S. Pat. No. 4,448,907, and are normally produced as the reaction product of an alkylene oxide and an amine compound. In general, any polyol containing at least one or more tertiary amine groups are considered to be within the scope of the definition of “aminopolyol”. 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 amine compounds which react with an alkylene oxide to yield the aminopolyol useful in the binder composition constituting this invention include ammonia and mono and polyamino compounds with primary or secondary amine groups. Specific examples include aliphatic amines such as primary alkyl amines, ethylene diamine, diethylene triamine and triethylene tetramine, cycloaliphatic amines such as cyclohexyl amine, pyrrolidine, morpholine and N,N′-diethylene diamine, aromatic amines, such as aniline, ortho-, meta-, and para-phenylene diamines, aniline-formaldehyde resins and the like. The aminopolyols typically have a hydroxyl number of from about 200 to 1000 mg/g KOH, preferably from about 600 to 800 mg/g KOH.
Polyester polyols that can be used are aliphatic and/or aromatic polyester polyols. Preferred polyester polyols are blends of liquid aromatic polyester polyols, which typically have a hydroxyl number from about 200 to 2,000 mg/g KOH, preferably from 200 to 1200 mg/g KOH, and most preferably from 250 to 800 mg/g KOH; a functionality equal to or greater than 2.0, preferably from 2 to 4; and a viscosity of 500 to 50,000 centipoise at 25° C., preferably 1,000 to 35,000 centipoise, and most preferably 1,500 to 25,000 centipoise. Aromatic polyester polyols are typically prepared by ester interchange of aromatic ester and alcohols or glycols by an acidic catalyst. Phthalates are typically used as aromatic esters to make aromatic polyester polyols. Examples of alcohols used to prepare the aromatic polyester polyols are ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propane diol, 1,4-butane diol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, trimethylol propane, tetramethylol methane, glycerin, and mixtures thereof. Aliphatic polyester polyols are typically made by direct condensation of the acid with the alcohol. Examples of acids used to prepare the aliphatic polyester polyols are succinic acid, glutaric acid, adipic acid, citric acid, tertrahydrophthalic acid, and mixtures thereof. Examples of alcohols used to prepare the aliphatic polyester polyols are ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propane diol, 1,4-butane diol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, trimethylol propane, tetramethylol methane, glycerin, and mixtures thereof.
Any organic polyisocyanate can be used in the Part II, the polyisocyanate component. The polyisocyanate component of the binder composition is generally employed as a solution in an organic solvent, but binders can be used in which the Part II consists of 100% polyisocyanate. The specific solvent concentration in the polyisocyanate component will vary depending on the type of phenolic resins employed in the Part I and its molecular weight. In general, the solvent concentration will be in the range of up to 80% by weight of the polyisocyanate component, typically in the range of up to 50%.
Examples of organic polyisocyanates used include polyisocyanates having a functionality of two or more, preferably 2 to 5. It may be aliphatic, cycloaliphatic, aromatic, or a hybrid polyisocyanate, or mixtures thereof. Representative examples of polyisocyanates are aliphatic polyisocyanates such as hexamethylene diisocyanate and 1,12-diisocyanatododecane, alicyclic polyisocyanates such as 4,4′-dicyclohexylmethane diisocyanate and isophorone diisocyanate, and aromatic polyisocyanates such as methylene diphenylisocyanate and its isomers and polymeric varieties, 2,6-toluene diisocyanate, and derivatives thereof. Other examples of suitable organic polyisocyanates are 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and derivatives thereof, and the like. Also, it is contemplated that chemically modified polyisocyanates, prepolymers of polyisocyanates, and quasi prepolymers of polyisocyanates can be used. Solid or viscous polyisocyanates must be used in the form of organic solvent solutions, the solvent generally being present in a range of up to 80 percent by weight of the solution, typically in the range of up to 50%.
The polyisocyanates are used in sufficient concentrations to cause the curing of the phenolic resin when catalyzed with a tertiary amine curing catalyst. In general the isocyanato group ratio of the polyisocyanate component to the hydroxyl groups of the polyol component is from 1.25:1 to 1:1.25, preferably about 1:1.
The Part I and/or the Part II of the binder contain one or more cycloalkanes as a solvent. The cycloalkanes are selected from the group consisting of unsubstituted cycloalkanes, substituted cycloalkanes, and mixtures thereof. Preferably, the number of carbon atoms in the cycloalkane is from 5 to 24, the number of rings, including individual fused, bridged, and spiro-connected ring arrangements in the cycloalkanes is from 1 to 4, and the number of carbon atoms in the individual rings of bi-, tri-, and tetracyclic cycloalkanes is from 3 to 10, preferably from 5 to 8. Examples of cycloalkanes that can be used as solvents in the Part I and/or Part II of the binder include, but are not limited to, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, norcarane, norpinane, norbornane, decahydroazulene, tricycle[2.2.1.0]hexane, tetracyclo[5,2,2,0,0]undecane, spiro[4.5]decane, dispiro[5.1.7.2]heptadecane, decahydronaphthalene, bicyclohexyl, tercyclodecane, 1-cyclobutyl-2-cyclopentylethane, perhydroantharacene, perhydrofluorene, their partially unsaturated congeners, alkyl, alkenyl and alkynyl derivatives, and mixtures thereof. Typically, the cycloalkane that will be used is decahydronaphthalene because it is the most readily and abundantly available cycloalkane.
The foundry binder may contain other solvents. In particular, the foundry binder may further comprise one or more solvents selected from the group consisting of aromatic hydrocarbon solvents, dibasic ester solvents, fatty acid ester solvents, and mixtures thereof, which may be formulated in the Part I, Part II, or both the Part I and Part II of the foundry binder.
The total amount of solvents in the binder typically ranges from 1 to 80 parts by weight based upon 100 parts by weight of the binder, preferably from 5 to 60 parts by weight based upon 100 parts by weight of the binder, and most preferably from 15 to 50 parts by weight based upon 100 parts by weight of the binder.
The total amount of cycloalkane in the binder typically ranges from 5 to 40 parts by weight based upon 100 parts by weight of the binder, preferably from 5 to 30 parts by weight based upon 100 parts by weight of the binder, and most preferably from 5 to 20 parts by weight based upon 100 parts by weight of the binder.
If the cylcoalkane is used in the Part I of the binder, the total amount of cycloalkane used in the Part I ranges from 0 to 30 parts by weight based upon 100 parts by weight of the Part I, preferably from 5 to 25 parts by weight based upon 100 parts by weight of the Part I, and most preferably from 5 to 20 parts by weight based upon 100 parts by weight of the Part I.
If the cylcoalkane is used in the Part II of the binder, the total amount of cycloalkane used in the Part II typically ranges from 0 to 60 parts by weight based upon 100 parts by weight of the Part II, preferably from 5 to 40 parts by weight based upon 100 parts by weight of the Part II, and most preferably from 5 to 30 parts by weight based upon 100 parts by weight of the Part II.
Foundry mixes are prepared by mixing a foundry refractory with the foundry binder. Various types of refractories and amounts of binder are used to prepare foundry sand mixes by methods well known in the art. Ordinary shapes, shapes for precision casting, and refractory shapes can be prepared by using the binder systems and proper refractory. The amount of binder and the type of refractory used are known to those skilled in the art. The preferred refractory employed for preparing foundry mixes is silica sand wherein at least about 70 weight percent, and preferably at least about 85 weight percent, of the sand is silica. Other suitable refractory materials for ordinary foundry shapes include zircon, olivine, aluminosilicate, chromite, and the like.
In typical foundry applications, the amount of binder is generally no greater than about 10% by weight and frequently within the range of about 0.5% to about 7% by weight based upon the weight of the refractory. Most often, the binder content for ordinary foundry shapes ranges from about 0.6% to about 5% by weight based upon the weight of the refractory.
The binder compositions are preferably made available as a two-part system with the polyol component in one part (Part I) and the polyisocyanate component as the other part (Part II). Usually, the polyol is first mixed with the refractory and then the polyisocyanate component is added, but the order of addition can be reversed. Methods of distributing the binder onto the refractory particles are well-known to those skilled in the art.
It will be apparent to those skilled in the art that other additives such as coupling agents, flow enhancers, benchlife extenders, release agents, drying agents, defoamers, wetting agents, etc. can be added to the binder, refractory, or foundry mix. The particular additives chosen will depend upon the specific purposes of the formulator.
In general, metal parts are made by creating a mold assembly with an internal cavity shaped to match the dimensions and profile of the metal part to be cast and a gating system to feed the hot liquid metal into the cavity. Molds and/or cores are inserted are inserted into the mold assembly to produce external and internal casting geometry that will shape the metal part when molten metal is poured into the mold assembly and cools. Optionally, a refractory coating can be applied to all or select components of the mold assembly that come in contact with the liquid metal.
Foundry shapes are prepared by a cold-box process comprising:
(a) introducing a major amount of a foundry mix into a pattern to form a foundry shape;
(b) contacting the foundry mix in the pattern with a vaporous curing catalyst;
(c) allowing the foundry shape to cure; and
(d) removing the foundry shape from the pattern when it is handleable.
Curing of polyol-polyisocyanate binders by the cold-box process is carried out by contacting the foundry shape with the vapor of a volatile tertiary amine as described in U.S. Pat. No. 3,409,579, which is hereby incorporated into this disclosure by reference. Examples of volatile tertiary amines, which can be used, include trimethylamine, dimethylethylamine, triethylamine, dimethylpropylamine, and the like.
Foundry shapes are prepared by a no-bake process comprising:
(e) introducing a major amount of foundry mix containing a liquid curing catalyst into a pattern to form a foundry shape;
(f) allowing the foundry shape to cure; and
(g) removing the foundry shape from the pattern when it is handleable.
The preferred liquid curing catalyst for the polyol-polyisocyanate binders is a tertiary amine and the preferred no-bake curing process is described in U.S. Pat. No. 3,485,797 which is hereby incorporated by reference into this disclosure. Specific examples of such liquid curing catalysts are amines which have a pKb value generally in the range from about 5 to about 11 and include 4-alkyl pyridines wherein the alkyl group has from one to four carbon atoms, for instance 4-phenylpropylpyridine, isoquinoline, arylpyridines such as phenyl pyridine, pyridine, acridine, 2-methoxypyridine, pyridazine, 3-chloro pyridine, quinoline, N-methyl imidazole, N-ethyl imidazole, N-vinyl imidazole, 4,4′-dipyridine, 1-methylbenzimidazole, 1,4-thiazine and (3-dimethylamino)propylamine.
Foundry shapes are prepared by a heat cured process comprising:
(h) introducing a major amount of foundry mix containing an refractory, a novolak resin and a polyisocyanate into a heated pattern to form a foundry shape;
(i) allowing the foundry shape to cure; and
(j) removing the foundry shape from the pattern when it is handleable.
The heat curing process is described in WO 2004050738 which is hereby incorporated by reference into this disclosure.
Metal parts are prepared by a process for casting a metal part comprising:
(k) inserting a foundry shape into a casting assembly having one or more molds and/or cores;
(l) pouring metal, while in the liquid state, into said casting assembly;
(m)allowing said metal to cool and solidify; and
(n) then separating the cast metal part from said casting assembly.
The metal parts can be cast from ferrous metals such as grey and white iron, ductile iron, compacted graphite iron and steel, and nonferrous metals such as aluminum, magnesium, copper, zinc, titanium and alloys thereof. The temperature of the molten ferrous metal ranges from about 1100° C. to about 1700° C. The temperature of the molten nonferrous metal ranges from about 400° C. to about 1700° C.
The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of.” The terms “a” and “the” as used herein are understood to encompass the plural as well as the singular.
Test foundry cores were made with by the cold-box process by first mixing Congleton HST 50 silica sand (from WBB minerals, Sibelco UK Ltd.) with the binder formulations described in Table I in a Kenwood Chef mixer for one minute. The phenolic resole resin (RESIN) used in the Part I of the binder was a polybenzylic ether phenolic resin prepared with zinc acetate dihydrate as the catalyst according to methods well-known in the art. The polyisocyanate used in the Part II of the binder was poly(rnethylene diphenylisocyanate) having a functionality of 2.7. Equal amounts of Part I and Part II were employed and the amount of the total binder used was 1.2 weight percent based on the weight of the sand.
The resulting foundry mixes were compacted into a cavity to produce test cores having dimensions of 120mm×22.4mm×6mm by blowing the foundry sand mix into a metal pattern where they were cured by the cold-box process as described in U.S. Pat. No. 3,409,579. The test cores were contacted with a mixture of triethylamine (0.25 ml) in nitrogen at a pressure of 1.4 bar for 1 second, followed by purging with nitrogen at a pressure of 4 bar for about 18 seconds, thereby forming the test specimen.
No objectionable odor was noticed when binders were prepared and the test cores were prepared.
Unless otherwise indicated, the test cores were made with a freshly prepared foundry sand mix and the transverse strength was measured 30 seconds, 3 minutes, and 6 minutes after the specimen was formed. Measuring the transverse strength of the test cores enables one to predict how the mixture of sand and binder will work in actual foundry operations. Lower transverse strengths for the shapes indicate that the phenolic resin and polyisocyanate reacted more extensively during and after mixing with the sand and prior to curing.
Examples A and B are comparison examples and do not contain any cycloalkane, while Example 1 is within the scope of this invention.
1Dibasic ester solvent
2Aromatic hydrocarbon solvent
3Fatty acid ester solvent
4Decahydronaphthalene
5Kilopascals
The data in Table I suggest that the transverse strengths of test cores made with the binder containing decahydronaphthalene (DHN) compare favorably to transverse strengths of test cores made with a commercially available phenolic urethane cold-box binder based on a typical aromatic hydrocarbon solvent (AHS) system and one based on fatty acid ester (FAE) and dibasic ester (DBE) solvents.
All publications, patents and patent applications cited in this specification are herein incorporated by reference, and for any and all purposes, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.
The foregoing description of the disclosure illustrates and describes the present disclosure. Additionally, the disclosure shows and describes only the preferred embodiments but, as mentioned above, it is to be understood that the disclosure is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art.
The embodiments described hereinabove are further intended to explain best modes known of practicing it and to enable others skilled in the art to utilize the disclosure in such, or other, embodiments and with the various modifications required by the particular applications or uses. Accordingly, the description is not intended to limit it to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/266,036 filed Jul. 16, 2009.
| Number | Date | Country | |
|---|---|---|---|
| 61266036 | Dec 2009 | US |
