Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS3816145 A
Publication typeGrant
Publication dateJun 11, 1974
Filing dateAug 31, 1972
Priority dateApr 15, 1970
Publication numberUS 3816145 A, US 3816145A, US-A-3816145, US3816145 A, US3816145A
InventorsMelcher R
Original AssigneeWhitehead Bros Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Trihydroxydiphenyl as an additive for foundry green molding sands
US 3816145 A
Tridydroxydiphenyl is useful as an additive for improving the properties of foundry green molding sands or clays. The trihydroxydiphenyl is incorporated into the sand in the form of an aqueous solution. Alternatively, the solution may be applied to the surface of a green sand mold for use as a facing agent.
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent 1191 Melcher June 11, 1974 TRIHYDROXYDIPHENYL AS AN ADDITIVE [56] References Cited Inventor: Ronald Melcher, o NJ. 2,753,312 7/1956 Miller .1 260/172 Assignee: Whitehead Brothers p y, 3,232,771 2/1966 Pearce [CG/38.35

Florham Park, NJ. Primary Examiner-Lorenzo B. Hayes 1221 Flled: 1 1972 Attorney, Agent, or Firm--Kenyon & Kenyon Reilly 211 Appl. No.: 285,277 Carr & Chapm Related us. Application Data [63] Continuation-impart of Ser. No. 28964, April 15, [57] ABSTRACT 1970. abandoned. Tridydroxydiphenyl is useful as an additive for improving the properties of foundry green molding sands US. Cl 106/3855, l 6/38.6, or clays. The trihydroxydiphenyl is incorporated into 260/DIG- 40 the sand in the form of an aqueous solution. Alterna- [51] Int. Cl B281) 7/34 tively, the solution may be applied to the surface of a [58] Field Of Search 106/383, 38.35, 38.6, green nd mold for use as a facing agent,

106/68; 260/DIG. 40, 37 R 15 Claims, 2 Drawing Figures 2-5 s' as Psmewr H MSM/SS/On 6 8 1 4-5 5 6.5 6 6-57 758 9 IO]! I2 14/6 1 TRIHYDROXYDIPHENYL AS AN ADDITIVE FOR FOUNDRY GREEN MOLDING SANDS The present invention relates to additives for foundry green molding sand. More particularly, this invention is concerned with the use of trihydroxydiphenyl as an additive for foundry green molding sand.

As is well known, the foundry art is that art dealing with the formation of metal articles by casting processes wherein molten metal is poured into a mold, allowed to cool, and solidify. By far the largest quantity of castings are made by processes in which the mold is formed from sand, i.e., by sand casting processes. There are several different sand casting processes, but the one employed most often is that employing green molding sand.

Green molding sand has been defined as a plastic mixture of sand grains, clay, water and other materials which can be used for molding and casting processes. The sand is called greenbecause of the moisture present and is thus distinguished from dry sand. (Heine et al., Principles of Metal Casting, McGraw-l-lill Book Co., lnc., New York (1955), p. 22). Green sand has also been defined as a a naturally bonded sand or a compounded molding-sand mixture which has been tempered with water for use while still in the damp or wet condition. (Molding Methods and Materials, lst Ed., The American Foundrymens Society, Des Plaines 1962). As employed herein, the term foundry green molding sand" has reference to green molding sands of the type known to and employed by those of ordinary skill in the foundry art comprising molding sand and clay and tempered with water. I

As is evident from the foregoing, the essential components of a foundry green molding sand are molding sand, clay and water. The molding sand, which usually is a silica sand(e.g., quartz), but which may be a zircon, olivine or other refractory particulate material having mesh sizes commonly in the range of from about 6 to about 270 mesh, serves largely as a filler and provides the body of the mold. The clay, which is a finely divided (normally less than about 2 microns) material such as montmorillonite, (bentonite), illite, kaolinite and the like, when plasticized with water, serves as a binder for the sand grains, and imparts the physical strength necessary to enable use of the green molding sand as a mold material. Ordinarily, green molding sands contain from about 5 to about 20 weight percent clay, based upon sand, and sufficient water, normally not greater than about 6 weight percent, based upon sand, to achieve the desired plasticity and other physical properties.

There are a number of properties which are desired in foundry green molding sands. Among the most important are:

1. Good flowability or compactibility to allow the sand to move against the pattern under compacting forces;

2. Good physical strength after compaction to permit the mold to retain its shape after removal of the pattern and during casting;

3. Dimensional stability during the casting process; 4. Good internal cohesion of the sand grains and poor adhesion of the sand grains to the cast article; and

5. Good collapsibility after casting to facilitate shakeout. There are, of course, subsidiary properties which are related to these properties, including compressive strength, permeability, compactibility, mold hardness,

' green shear, deformation, peel, and the like. In general,

a green molding sand typically has properties within the following ranges:

Green Compression Strength 4 psi Green Shear Strength 0.5 10 psi Deformation 0.005 0.04 in/in Permeability 6.5 400 Dry Compression Strength 50 200* psi If the deformation is too low, the green molding sand is too brittle and cannot withstand handling and pattern removal, while if the deformation is too-high dimensional accuracy cannot be maintained, and the mold,

nology. If permeability is less than 6.5, the vapors generated during casting cannot dissipate rapidly enough,

and the mold can rupture from gas pressure and molten metal can be ejected out of the sprues. If, on the other I hand, the permeability is too high, the molten metal V will not be retained in the mold cavity, but will penetra'te the voids of the sand. Finally, if the dry strength is too low the sand cannot withstand the erosive effect of the flowing molten metal during casting, while if the dry strength is too high the casting may crack upon solidification.

ln general, foundry green molding sands consisting solely of sand, clay and water do not possess an optimum balance of properties. For this reason, a variety of additives have been employed in an effort to improve the properties of green molding sands. Typically these additives are organic materials which are used as facing agents, expansion control agents and the like. In most cases these organic additives are useful in improving only one property of they green sand and thus two or more additives may be required. In addition, an additive employed to improve one property frequently has an adverseeffect on another property of the green sand mold.. For example, sea coal or bituminous coal has been used as a facing agent, and while it does prevent bum-on, it has been found that increased amounts of clay and water are necessary to restore desirable physicalproperties possessed bythe unmodified green sand.

The use of such organic additives is further limited because the total amount of materials which form gaseous materials under the elevated temperatures encountered during casting (i.e., water and organic additives) must be kept below about 10 weight percent, based upon sand. Excessive amounts of organic materials lead to the generation of more gas than can be dissipated by permeation through the mold body, and would lead to the failure of the mold and the generation of defects in the casting. Normally, the loss of weight on ignition due that an aqueous solution of trihydroxydiphenyl is useful as an additive for foundry green molding sands. More importantly, it has been found that an aqueous solution of trihydroxydiphenyl is unique as a foundry green molding sand additive in that it has a beneficial effect ganic additive to green molding sand, regardless of the casting being made.

In particular, the use of aqueous trihydroxydiphenyl in accordance with this invention affords the following advantages:

l. The molding sand has good flowability. Thusthe sand is readily formed and compacted around mold patterns of complicated design. Moreover, the sand can be readily employed in automatic molding machines. In addition, the good flowability permits achievement of a desired sand hardness and apparent bulk density with the expenditure of less compacting energy than other green molding sands. Further, the danger of overramming a portion of the mold due to variations in compacting energy is reduced due to more uniform compaction of the sand. Thus the rammed sand is more homogeneous with respect to density and therefore strength. I

2. The compacted sand possesses desirable green strength characteristics at lower moisture contents than are achieved with conventional green molding sands.

3. The additive acts as a facing agent, and prevents burn-on or the fusing of quartz sand grains to the surface of the casting, and promotes excellent finish and peel.

4. The additive reduces shifting of the sand during the casting process, whether it be mold wall movement or enlargement of the mold cavity, or whether it be a locallized shifting of the sand resulting in such casting defects as rat-tails, scabs and buckles.

5. The additive permits casting to be effected at lower pouring temperatures and promotes increased fluidity of the metal during casting.

6. The additive yields adequate dry compression strength and yet excellent shakeout is obtained even with green molding sands employing Western bentonite as the clay binder.

'7. Finally, the additive is employed at relatively low levels, which in turn minimizes the formation of gas during casting. 1

Without wishing to be bound by theory, it is believed that the superior utility of the additive ,of this invention is due, in large part, to the hygroscopic nature of trihydroxydiphenyl, for it is this property which enables the use of green molding sands having reduced moisture content. As noted above, green molding sands normally contain up to about 6 weight percent and typically from about 3 to about 6 weight percent water. When the moisture content of the conventional sands is less than about 3 weight percent, e.g. is 2 weight percent, the water evaporatesout so rapidly that the sand does not have a useful working life, and at moisture contents of 1 weight percent the sand is not cohesive and cannot be formed into a mold. The trihydroxydiphenyl, on the other hand, because it is hygroscopic, acts as a humectant, and enables the green molding sand to retain its moisture content at moisture levels as low as 1 weight percent or even less. Indeed, the hygroscopic properties of the resins are so pronounced that the sand can be retempered without the mulling heretofore required. For example, when dry, particulate RM 441 is allowed to stand at C. and 80 percent relative hu-' midity it picks up about 53 percent of its own weight of water. Thus, retempering can be effected by allowing the molding sand to stand in an atmosphere having a high, e. g., at least about 80 percent, relative humidity. Alternatively, water can be sprinkled on the sand and allowed to equilibrate after'only a minimal degree of mixing or processing effort and time. it is also believed that the trihydroxydiphenyl, like the water, is a plasticizer for the clay binder, and it is this property which enables the formulation of a cohesive green molding sand at low moisture contents, eg 1 weight percent.

The reduced water content of the green molding sand is believed responsible for a number of advantages. First, less total gas is generated during the casting cycle. The reduction in the amount of gas produced decreases, the amount venting or permeability necessary to allow the gas to escape. As a consequence, sands having higher A.'F.S. fineness numbers can be used, thus providing a better casting finish. Secondly, the reduced amounts of water result in the virutal absence of a condensation zone or zone of high moisture content resulting from water vapor transported from the heated mold surface, in the mold mass during the casting cycle. The absence of this zone elminates defects, such as rat-tails, buckles and scabs normally associated with separation of the dry crust at the mold surfacefrom the body of the mold due to the weaker bond strength in the condensation zone.

The reduced amounts of water in the mold body permits the use of lower pouring temperatures during casting, since the metal will not be chilled as much through loss of heat to vaporize the water. As a corrolary to this, the molten metal can flow into thinner and more complexpassages without the need for the more elevated temperatures required by current practice. Thus the use of trihydroxydiphenyl contributes to improved metal fluidity and reduces misruns or cold shut.

The reduced amount of water also tends to reduce the degree of burn-on and-provides better facing action. lt is known that the water present in green sand molds, when heated to casting temperature, provides an oxidizing atmosphere which contributes to burn-on. This contribution is minimized by reducing the water content of the sand.

The reduced amount of water also reduces pinhold porosity of the casting. lt is known that water will decompose m its constituent elements, hydrogen and oxygen, at casting temperatures. The hydrogen thus formed can dissolve in the molten metal, causing gas defectsknown as pinhole porosity. These defects are reduced when the amount of water in the green sand mold is reduced.

Finally, the reduced moisture content of the sand is believed responsible for improved shakeout, especially when Western bentonite is employed as the clay binder. It is known'that the dry compression strength developed with green molding sands employing Western bentonite increases with increasing moisture content of the green sand. Since a reduced moisture content is feasible with applicants invention, reduced dry strengths and thus improved shakeout result.

The trihydroxydiphenyl has other properties which contribute to its desirability as a green molding sand additive. Thus, on pyrolysis, the trihydroxydiphenyl forms a fine, honeycomb, coke-like structure which, it is believed, tends to lock up" the sand grains with a bond in addition to that afforded by the clay. This bond further retards shifting of the sand grains and, in particular, is believed responsive for limiting mold wall movement and cavity enlargement. ln addition, the trihydroxydiphenyl, like other carbonaceous materials, forms a non-oxidizing atmosphere at casting temperatures, which contributes to its facing activity.

Still another desirable property of trihydroxydiphenyl is its apparent ability, in combination with the clay binder, to impart lubricity to the sand grains comprising the green sand, and to permit them to slide past one another prior to compaction. lt is this property which is believed responsible for the good flowability of the uncompacted green molding sand, as well as the ability of the sand to be compacted to high apparent bulk densities with the expenditure of reduced compacting energy. Moreover, the increased flowability reduces the criticality of variations in compacting energy over the mold, and renders the sand less susceptible to expansion defects caused by non-uniform ramming of the mold. As a result, excellent molds can be made even by less skilled molders. Despite the good flowability of the uncompacted sand, the trihydroxydiphenyl imparts a strong cohesion of the sand grains of the compacted sand. Generally the cohesion is higher than that of the adhesion of the sand to the metal, thus rendering parting agents unnecessary. Thus, fine details are not lost.

Regardless of the mechanism of its mode of action, however, trihydroxydiphenyl has proven to be a unique additive for foundry green molding sands, and is responsible for the improvement of a great number of the properties of the molding sand. As a result, no other organic additive need be employed. Moreover, the aqueous trihydroxydiphenyl can be employed as a substitute for so-called waterless additives, such as the known bentone-based oleophilic materials. Unlike these materials, whose utility is limited to casting aluminum and light metals, the aqueous trihydroxydiphenyl can be employed for casting all types of metals.

Ahtough trihydroxydiphenyl has been found by this invention to be useful as a foundry green molding sand additive, and it can be employed as such in pure form if desired, such use is presently uneconomical. It has been further found, however, that crude forms of trihydroxydiphenyl can be employed satisfactorily. A suitable form of crude trihydroxydiphenyl is the solid resinous material as a still residue remaining after the distil-' lation of technical grade resorcinol. Residues of this type, as well as the recovery of 2,3,4- trihydroxydiphenyl from them, have been described by William E. St. Clair in U.S. Pat. No. 3,133,033 issued May 12, 1964 and by William H. Voris in U.S. Pat. No. 3,347,884 issued Oct. 17, 1971, as comprising 55 percent trihydroxydiphenyls, plus minor amounts of resorcinol, dihydroxydiphenyl and monohydroxydiphenyls, with the chief ingredient being 2,3,4- trihydroxydiphenyl. A resinous material of this type is commercially available from Koppers Company under the trade designation RM 441.

RM 441 has been described by Paul G. Gemeinhardt in U.S. Pat. No. 3,330,781 issued on July 11, 1967, and by Loren J. Miller in U.S. Pat. No. 2,753,312 issued July 3, 1956 as follows: I

RM 441 is a designation given by Koppers Company to a solid resinous material, which is obtained by them as a residue remaining in the still after removing technical grade resorcinol as a distillate. A typical ultimate chemical analysis of this material (the percentages given being by weight) is as follows:

Physically, RM 441 is a drak brown, brittle material having the following characteristics:

Ball and ring softening point, C. to 88 Water solubility, percent 20 to 25 lsopropyl alcohol solubility, percent 94 to 98% If technical grade resorcinol is heated at about 200C, there is produced a dark coloredmaterial appearing and responding similarly to all the tests above given as "to RM 441. Thus, RM 441 is believed to consist essentially of a condensation product (or mixture thereof) derived from resorcinol under the influence of heat. It is also known, due to its origin, that RM 441 in its present commercialform contains relatively small amounts of impurities normally occurring incident to the commercial manufacture of technical grade resorcinol, for example, small or trace amounts of 3 mercapto phenol (C H OHSH).

RM 441 can be distilled at low pressure to give about 55 percent of a yellow oily distillate, which will partially crystallize. The crystals amount to about 60 percent of the distillate (33 percent of the original RM 441), and melt at about l36C. These crystals, when analyzed correctly, are found to be trihydroxydiphenyl the positions of the hydroxyl groups on the two rings being unknown. The oilyportion of the distillate, representing about 22 percent of the entire RM 441, also contains trihydroxydiphenyl, again with the positions of the hydroxyl groups unknown. There is also identified in this oily portion small portions of dihydroxydiphenyl, again with the positions of the hydroxyl groups unknown. The balance of the RM 441 has not been fully or positively identified, but is believed to contain further condensation products of resorcinol, similar in some respects to the trihydroxydiphenylabove referred to, and including compounds havinga plurality, probably three or more, phenyl groups linked in either straight or branched chains and with some -Ol-l groups thereon. This material is believed to be created by the polymerizing or coupling action of heat upon -resorcinol, eliminating water, probably similar to' a linkage formed between two resorcinol molecules as follows:

momma-wallowin resulting in the chaining together, in either straight or branched chains or both, of a number of the original resorcinol molecules. It is further believed that in most instances there is at least one Ol-l group remaining on each of the phenyl rings, although this has not been identified. Furthermore, in an end group of a chain, it seems likely that there are two hydroxyl groups remaining on the ring. For example, a compound of the kind visualized could be expressed by the formula:

Again, in this group of compounds, which is assumed to be reasonably representative of a substantial portion of the RM 441 the positions of the several remaining OH groups are unknown. It is believed that RM 441 or a material substantially equivalent and which should for the purposes of the present application be considered as RM 441, is also fonned when pure resorcinol is heated to 200C., probably due to one or more molecules of water splitting off, leaving in each instance a phenol ring deficient in hydrogemthen the phenol molecular deficiency is subject to attachment to another ring as well as with resorcinolper se in order to blance the molecules.

' While there is herein included not only specific technical data which has been exactly obtainedas to the characteristics of RM 441, there is also included all that is presently known of this material. It will be understood that any theory expressed therein in'this connection is given for what it may be worth, and is not to be considered as specifically limiting upon the definition of the material, but that any material derived from the sources above set forth and/or having physical and chemical characteristics generally similar to that particularly described for RM 441,.is to be considered as RM 441 for the purposes of this application, including the claims appended hereto.

It will further be understood that inasmuch as RM 441 is obtained commercially as a still residue, and as the distillation operation by which it is produced may be a batch operation, the composition may differ somewhat from time to time.

RM 441 may be briefly defined as a solid resinous material comprising a residue remaining in the still after removing technical grade resorcinol as a distillate.

Contrary to the above teaching that RM 441 is soluble in water only inamounts of up to about 25 percent,

it now has been found that aqueous solutions contain: ing up to about 99 parts of RM 441 per part water can be prepared. Indeed, the aqueous solution characteristics of RM 441 appear to be much more complex than implied by the above-quoted reference. Specifically, when RM 441 and water are mixed in proportions of less than about 0.25 to about 0.35 parts resin per part water, there is obtained a milky suspension which, after standing for a few minutes, forms a water-insoluble, black tarry residue comprising about 8-10 percent of the product and which contains about 18 to 19 weight percent water. The residue will redissolve on increasing the solids content to above about 25 percent, and at proportions of RM 441 to water above from about 0.25 to about 0.35 parts resin per part water there is formed a two-phase system comprising a minor amount (generally not more than about 1.2 weight percent of the total) of a solid'dispersed in a clear, dark red or brown, slightly acidic solution having a composition substantially equal to that of the total composition. For example, if 2 parts of resin are admixed with 1 part of water there is obtained a mixture comprising about 0.03 parts of solid and the balance a solution of about 2 partsof solute in 1 part of water having a pH-of about 5.2. Because the density of the solid is close to that of the liquid phase, especially at higher ratios of resin to water,

it does not readily settle but it can be isolated through techniques such as filtration or centrifugation. The

pure solid is a white, crystalline material, and when admixed with an equal amount of water, dissolves upon heating to a temperature of at least about 59F. This solid can also be dissolved by making the aqueous composition alkaline (pH greater than 7), as by the addition of ammonia or an alkali metal hydroxide, e.g., lithium, sodium or potassium hydroxide.

The aqueous solutions are prepared by any convenient technique, but preferably by adding heated water to F. to particulate resin having a particle size of not greater than about 2 inches in the desired proportions. The resulting mixture is then stirred to promote dissolution and base may be added if desired. It is not necessary that the solution be free of any undissolved solid, although the solid can be removed if desired.

it has been further found that distillation fractions of RM 441 are useful in accordance with this invention. For example, aqueous solutions of the abovementioned only distillate and the residue resulting therefrom are useful in accordance with this invention. However, solutions of the distillate are somewhat less active and solutions of the residue are somewhat more active than solutions of the resin RM 441 for the applications discussed below.

The distillate, if added to water in a weight ratio'in excess of 121, forms a solution, especially on heating, and the solution can bediluted without forming a precipitate. If, however, the initial solution is allowed to stand for one or two days, crystallization occurs and, upon dilution, a pearlescent precipitate forms which can be redissolved by the addition of base as described above or upon heating. It is to be noted that the aqueous solutions of this invention includes those which are free of suspended matter, such as the alkaline or heated solutions mentioned above as well as solutions including the insoluble solid.

The similarity of RM 441 to pure trihydroxydiphenyl is evidenced by the similarity of their infrared spectra as set forth in FIGS. 1 and 2, of which FIG. 1 is the spectrum for 98 percent pure 2,3,4- trihydroxydiphenyl and FIG 2 is the spectrum for RM 441.

Although RM 441 is the only acceptable source of crude trihydroxydiphenyl presently known to applicant to be available on -a commercial basis, it is contemplated by this invention that similar resinous materials containing a substantial proportion (i.e., at least 50 weight percent trihydroxydiphenyl) may likewise be employed without departing from the spirit of this invention. Accordingly, as employed herein, trihydroxydiphenyl has reference to the pure compound as well as to resinous compositions containing a substantial proportion of the hydroxydiphenyl.

It is essential 'to this invention that the trihydroxydiphenyl be employed in the form of an aqueous solution, for the additive alone is of little or no practical use as afoundry green molding sand additive. It is believed that the water performs a function over and above that of a mere diluent, and that the plasticizing action of the solution is greater than that of the trihydroxydiphenyl .or water separately.

The amount of trihydroxydiphenyl in the aqueous solution can vary widely, and generally will be in the range of from about 0.1 part to about 10 parts per part of water. However, the advantage of low water content in the foundry green molding sand is not achieved unless the aqueous composition contains at least about 0.5 parts trihydroxydiphenyl per part water, and preferably at least about 1 part per part water. Moreover, concentrations in excess of about 5 parts trihydroxydiphenyl per part water ordinarily are too viscous to permit ready distribution throughout the sand. A ratio in the range of from about 1 to about 2 parts trihydroxydiphenyl per part water is preferred. A solution of equal parts trihydroxydiphenyl and water is especially preferred, since green molding sands made employing more concentrated solutions tend to creep, especially in large mold masses (i.e., 100 pounds or more).

Higher green strength and shear values are obtained in the green molding sand when the solution also contains a water soluble hydroxide in amounts of up to about 25 percent, based upon the weight of the resin. Alkali metal hydroxides, especially sodium hydroxide, are preferred, although ammonium hydroxide is also useful. Preferred amounts are in the range of from about 1 to about weight percent, more preferably from about 5 to about 10 weight'percent.

Although it is in principle possible to blend dry trihydroxydiphenyl with sand and clay and then add water, thereby forming the solution in situ, it has been found that as a practical matter the solution must be formed and then admixed with the sand, clay and, if necessary, additional temper water. When dry hydroxydiphenyl is blended with the sand and clay and water is subsequently added, long delays, generally 12 to 24 hours, are encountered before the clay is plasticized and useful green strength is developed. In contrast, when an aqueous solution is admixed with sand andclay, plasticization occurs within 5 minutes and thus the sand is ready for use upon mixing. The amount of solution added to the sand is not critical, provided it is present in an amount sufficient to impart the desired property, be it cohesion, facing activity, tempering, plasticity or the like. Normally this amount will be less than about 5 parts per 100 parts sand withfrom about 1 to about 3 parts being most usual.

The solution is admixed with the sand and clay in any suitable manner. The temperature of the solution is not critical provided the solution is sufficiently fluid to be easily dispersed throughout the sand or clay. For example, a composition composed of 2 parts RM 441 and 1 part water may be used at a temperature within the range of from about 32F. to about 120F.

The additive can be mixed directly with a natural or synthetic molding sand, or it can be added in combination with other additives, such as clay binders of the bentonite, ilite or kaolinitic type. In this regard, it has been found that the additive acts as an activator and plasticizer for clays of this type, and these compositions are able to develop high green strength with the attendant advantage of low water content imparted by the clay binder. Thus a molding sand including both the additive of this invention and a clay binder has extremely desirable properties. i

Although the trihydroxydiphenyl solution is most commonly admixed with the sand prior to forming the green sand mold, it is also useful as a face dressing or facing agent and can beapplied to the mold surface after the mold has been formed.

The solution may be applied to the mold surface by any convenient technique, as by brushing or spraying, with spraying being preferred. When spraying is employed, airless spray techniques are preferred to minimize the incidence of air-entrained particles. The solution diffuses into the sand at the mold surface without leaving a residueat the surface. Thus there is no loss of detail, such as is encountered with commonly employed surface sprays or washes containing fine particles of an inorganic refractory material.

The concentration of the trihydroxydiphenyl is not critical, provided the solution has a consistency which pennits its application to the mold surface and yet contains sufficient resin to permit application of the desired amount to the surface without requiring excessive amounts of solution. In general, however, amounts of trihydroxydiphenyl varying from about 0.35 to about 3 parts per part water have been found satisfactory for application as a spray.

The following examples are illustrative. All parts and percentagesare by weight unless otherwise specified.

EXAMPLE 1 Molding sand compositions containing 400 parts Ottawa A.F.S. Testing Sand, 24 parts anhydrous clay and either 12 parts of a 2:1 solution of RM 441 in water or 12 parts water as a control were made up. Those containing water only were prepared by mulling clay and sand for 5 minutes, adding water and mulling for 10 minutes, whereas those containing RM 441 solution were prepared by mulling sand plus solution for 5 minutes, adding the clay and mulling for 10 minutes. Comparative testing was performed on compositions employing either Western Bentonite, Southern Bentonite, Cedar Heights fire clay or Bondrite Bond Kaolinitic Clay as the clay, and the molding sand compositions were evaluated for percent moisture, green compressive strength, green shear strength and green deformation. The data are summarized in tabular form as follows:

Table l A Physical Properties of Molding Sands Green Green Green Deforcompr. shear mation, Compositions Moisture str.,psi str.,psi in/in.

W. Bentonite Clay Test 0.8 9.2 3.7 Control 3.0 8.7 2.4 0.23

S. Bentonite Cla lest 0.72 10.2 3.7 Control 2.4 10.0 2.6 0.030

Cedar Heights clay Test 0.7 4.0 1.2 0.025 Control 2.6 2.8 0.6 0.02l

Bondrite Clay Test 0.72 5 3 1.6 0.022 Control 2 6 3 5 0.8 0.02l

" Plastic deformation.

It is readily apparent that the molding sand test compositions incorporating the aqueous RM 441 were su: 'perior to their corresponding controls in green physical properties, despite the presence of less than 1 percent water in the molding sand.

EXAMPLE 2 Molding sand compositions composed of 100 parts AFS 80 sand, 5 parts Western Bentonite and 2.5 parts of a 2:1 solution of RM 441 in water were employed under commercial casting conditions to make castings of gray iron, Navy M and 85-5-5 copper based alloys and aluminum. 1n all instances the castings were free from rat-tails, buckles and scabs and-exhibited improved surface smoothness, reduced casting weight (generally 3.0 to 4.5 percent less), and closer conformity to pattern size when compared with castings made employing conventional moldingsand compositions. Similarly superior results were obtained employing a formulation composed of 100 parts AFS 130 sand, 6 parts Western Bentonite and 3 parts of a 2:1 resin RM 441/water solution.

EXAMPLE 3 A test sand containinga 2:1 solution of RM 441 in water and a control-sand were used to make iron castings at 2, 700F. using 50 percent new iron ingot and 50 percent remelt iron. The pattern employed consisted of a polystyrene cylinder having a length of about 8 3/16 inches and a diameter of about 2.5 inches and one end thereof sealed off with an aluminum disc having mounted thereon an aluminum cube having 0.995-inch square sides. The molds were made up so that the parting line was at the juncture of the cylinder and the disc, with the cube being below the parting line in the'drag.

The test sand comprised 200 parts New Jersey A.F.S. 130 Fineness Sand, 6 parts of the resin solution and 12 parts of Western Bentonite retempered with about 1 percent water to provide amixture having a moisture content of 1.2 percent. After ramming, the mold hardness around the drag edge of the pattern was 7882. After casting, the cube portion was measured to determine its dimensions from the centers of its opposing sides and from the centers of its opposed top edges. The side-to-side shrinkage of the cube was 0.007 inch and 0.01 1 inch, or slightly less than the normal shrinkage of 1 inch of iron (0.013 inch), and the edge-to-edge shrinkage was 0.004 inches in one direction and zero in the other.

The control sand was composed of 200 parts New Jersey A.F.S. 130 Fineness Sand, 6 parts Southern Ben- I tonite, 6 parts Western Bentonite and 7 parts water. The mold hardness around the drag edge of the pattern was 78 to 85. Measurements of the cube showed a sideto-side gain of 0.008 inches, and an edge-to-edge gain of 0.020 inches in one direction and 0.025 inches in the other.

After making allowance for the natural shrinkage of iron, one can compute the extent of mold wall movements. For example, using the side-to-side dimensional shrinkage from the pattern dimension of 0.007 inches, the mold wall movement would be 0.013 less 0.007 or 0.006 inch. The calculated mold wall movements are summarized as follows:

Table 11 Mold Wall Movement inches Sand Composition side-to-side edge-to-edge Test 0.002; 0.006 0.009; 0.013 Control 0.021 0.033; 0.038

It is readily apparent that there was little or no mold wall movement when the resin solution of this invention was employed in the sand, whereas there was considerable mold wall movement in its absence.

EXAMPLE 4 EXAMPLE 5 Employing a sand composed of parts New Jersey A.F.S. Fineness Sand, 3 parts Southern Bentonite, 3 parts Western Bentonite and 3.5 parts water, a 2- cavity mold was prepared to make two step castings,

each having a rectangular drag surface measuring 4 inches by 12 inches, a cope surface provided with three steps measuring 4 inches by 4 inches, and thicknesses of one-half inch, one inch and 2 inches. One cavity was sprayed with a solution of 2 parts of RM 441 in 1 part of water and the other with a solution of equal parts molasses. and water commonly used as a mold surface dressing agent. Casting was with grey iron (50 percent new iron) at 2640F., and shake out was after 45 minutes. The casting made in the cavity sprayed with the RM 441 solution had a light bum-on on some of the drag surface, and the sides had somewhat heavier burnon, while the tops of the steps were perfectly clean. In comparison, the casting from the cavity sprayed with molasses had severe burn-on on all surfaces.

EXAMPLE 6 Employing an 8.5-inch by 8.5-inch by 0.5-inch plate as a pattern, a mold was made of a composition containing 100 parts New Jersey A.F.S. Fineness Sand, 3 parts Southern Bentonite, 3 parts Western Bentonite and 3.5 parts water, and provided with two gates at one of the cavity surface adjacent the other gate was sprayed withTop Bond, a commercially available top dressing. The mold was cast at 2750F. using about 60 percent new iron and the casting was removed after about 1 hour. All of the sand in the path of themetal on the surface sprayedwith Top Bond washed away,

while about 25 percent of the sand on the side sprayed with RM 441 remained in place in the path of the metal. Thus the RM 441 proved to be a superior top dressing. The surface of the casting corresponding to the mold surface which was not sprayed exhibited sematerial being a dark brown, brittle material having a ball and ring softening point of 80C. to 88C. and an isopropyl alcohol solubility of 94 percent to 98% percent, the proportions of water and the said resinous maaqueous solution of a solid resinous material comprising a residue remaining in the still after removing technical grade resorcinol as a distillate, said solid resinous vere burn-on. 5 terial in said aqueous solution and the amount of said EXAMPLE 7 solution in said molding sand being sufiicient to impart A series of solutions of equal parts RM 441 and a sol-, lmpl'qved greer} sand propajmes to sfild composlhtlonj vent were prepared. Each of the solutions was then em- P according to clalm 6 wherem i l d to prepare a ldi d composition i solution contains from about 1 to about 2 parts of said ing 1,500 parts of dry No. 24 sand, 90 parts of anhyl0 resinous materlal P P 1 Water; drous bentonite and 45 parts of the solution. Each of 8. A composition according to claim 6 wherein said the resulting compositions .were evaluated for moisture solution contains about equal parts of said resinous macontent, the weight of a 2-inch specimen, green comterial and water. pression strength, green shear strength, green deforma- 9. A foundry molding sand according to claim 8 contion and mold hardness. 'The results of these experil taining up to about 5 parts of said solution per 100 ments are summarized as follows: parts of sand.

Sand Composition Property I o I Deforrn- Hard- Moisture Weight Compr. Shear mation, ness Solvent gm str.psi str.psi in/in psi Propylene 0.06 140 2.1 0.6 w 70 glycol Triethylene 0.06 145.5 1.66 0.57 62 glycol Methyl ethyl 0.06 150.7 1.22 0.47 0.0240 66 ketone n-Hexanol 0.06 154.8 0.65 0.37 0.0188 58 Glycerine 0.06 139.0 2.36 0.74 w 69 Furfuryl alcohol 0.06 146.0 1.96 0.63 0.0325 70 lsopropanol 0.06 152.0 1.01 0.35 0.0236 63.5 Acetone 0.06 141 2.67 0.84 0.0365 72 Diethylamino 0.06 152 1.23 0.42 0.0247 64.6

propylamine Ethylene glycol 0.03 139 2.90 0.93 71 Water 1.10 147 6.46 1.66 0.0185 82 Sand dried rapidly, becoming friable.

From the foregoing data, it is evident that only the 1 foundry molding Sand according to claim 8 aqueous solution of RM 441 provided a sand composicontaining from about 1 to about 3 parts of said solution combining high compression strength, shear tion per 100 parts of said sand. strength and hardness and low deformation. 11. A foundry molding sand according to claim 8 What is claimed is: 1 wherein said aqueous solution contains up to about 1. In a foundry green molding sand composition com- 0.25 parts of a dissolved, water-soluble hydroxide per prising molding sand, clay and water, the improvement part of said resinous material. comprising trihydroxydiphenyl in the form of a solution 4 12. A foundry molding sand according to claim 11 of trihydroxydiphenyl dissolved in water uniformly ad- 5 wherein said hydroxide is an alkali metal hydroxide. mixed with said composition, the concentration of 13. A foundry molding sand according to claim 12 trihydroxydiphenyl in said solution and in said compowherein said aqueous solution contains from about s1tion being sufficient to impart improved green sand 0,01 t ab ut 0 15 a ts f s di hydroxide per part properties to said composition. of said resinous material.

. 2. A composrtlon according to claim 1 containing up 14. In a foundry green molding sand composltion to about 5 parts of said solution per 100 parts of moldcomprising molding sand, clay and water, the improveing sand. ment comprising from about 0.35 parts to about 99 3. A composition according to claim 1 containing parts of a solid resinous material comprising a residue from about 1 to about 3 parts of said solution per 100 remaining in the still after removing technical grade parts of molding sand. resorcinol as a distillate, said solid resinous material 4. A composition according to claim 1 wherein said being a dark brown, brittle material having a ball and solution contains from about 1 to about 2 parts of trihyrlng f ening pomt of 80C to 88C. and an isopropyl droxydiphenyl per part of water. alcohol solub111ty of 94 percent to 98% percent and 1 5. A composition according to claim 4 wherein said P rt Of Water, id aqueous solution being present in an solution contains about equal parts of trihydroxydipheamount suf ficlent t0 lrnpart lmproved green sand propd water ertres to said composition.

6.1n a foundry green molding sand composition com- A 1 1 0911 a rding to claim 14 wherein prising molding sand, clay and water, the improvement Said q p 9 comprises from about t0 comprising m ldi sa d if r ly ad i d ith an about 5 parts of said resinous material per part of water and up to about 0.25 parts of a dissolved, water-soluble hydroxide per part of said resinous material.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2753312 *May 21, 1952Jul 3, 1956American Hard Rubber CoProcess of making acid-resistant molded articles containing organic fibers, resorcinol residue and asphalt
US3232771 *Jun 29, 1962Feb 1, 1966Pearce John WMolds and methods of preparing same
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3954695 *Jul 13, 1973May 4, 1976Manley Bros. Of Indiana, Inc.Molding composition with resin coated refractory
US4131476 *Aug 5, 1977Dec 26, 1978Whitehead Brothers CompanyAdditive for green molding sand
US4387173 *Apr 16, 1981Jun 7, 1983General Refractories CompanyUse of resorcinal polymer blend as a binder for carbon-containing refractory brick and shape
US4391642 *Feb 4, 1980Jul 5, 1983Foseco International LimitedAlkali metal silicate binder compositions
US4636262 *Mar 11, 1986Jan 13, 1987Reed Edgar HAdditive for green molding sand
DE2834065A1 *Aug 3, 1978Feb 22, 1979Whitehead Bros CoAdditiv fuer einen formsand
DE3212671A1 *Apr 5, 1982Nov 18, 1982Gen Refractories CoFeuerfeste, kohlenstoffhaltige steine und massen sowie deren verwendung
U.S. Classification106/38.35, 106/38.6, 501/129
International ClassificationB28B7/38, B22C1/16, B22C1/20
Cooperative ClassificationB28B7/384, B22C1/20
European ClassificationB28B7/38C, B22C1/20