MXPA96003351A - Agglutinants for hearts and molds - Google Patents

Abstract

The present invention relates to an inorganic binder system for casting compositions that includes an added silicate and phosphate. The composition produces a binder having advantageous strength properties for a silicate binder system having the dispersibility properties of a phosphate binder system. The methods for preparing and using the binder systems and the resulting products are of particular interest for the foundry technique

Description

BINDERS FOR HEARTS AND MOLDS FIELD OF THE INVENTION The present application is generally related to systems of inorganic binders cured by heat for particulate material, which has utility in the manufacture of molds, cores, mandrels or other conformations that can be used in the production of metallic and non-metallic parts.

BACKGROUND PE THE INVENTION Organic and inorganic systems are currently used as binders in the formation of conformations from a mixture containing an aggregate material such as sand. Normally, the aggregate material and the binder are mixed, the resulting mixture is tamped, blown or charged in a pattern to form a desired shape and then cured with the use of a catalyst, a co-reactant and / or heat to a state solid cured These binders find use in many applications to bind particulate material and are frequently used in foundry applications. The most acceptable binder systems used in the foundry technique are organic binder systems. A particular organic system used as a binder in the casting technique is a urethane binder. The two main components of this system are a polyhydroxy component and a polyisocyanate component. These two components are added to an aggregate and are cured. In the "cold box" process a gaseous amine catalyst is used to catalyze the reaction between the polyhydroxy component and the isocyanate component to form a conformation. This system does not require heating to achieve curing (see for example U.S. Patent Application No. 08 / 285,108 filed August 3, 1994 and incorporated herein by reference). In another process, the process of "hot box" the aggregate, the binder and the catalyst are mixed and then blow or charged in a hot pattern. The curing is effected by transferring heat from the standard to the aggregate mixture. Without taking into account the type of organic binder system, the organic binder used to produce desired conformations will volatilize during curing and / or burning at the metal casting temperature. These processes produce smoke, odors and additional undesirable and dangerous emissions that may make it necessary to restrict them to local and central government regulations. Another shortcoming of organic binder systems is their relatively short bank life. To eliminate the deficiencies of organic systems, some smelters use inorganic binders systems. One type of inorganic binder that is widely applied is an aqueous solution of a silicate such as sodium silicate, i.e., liquid glass (see U.S. Patent No. 4,226,277 incorporated herein by reference). Although the binding properties of the silicates are generally satisfactory, when compared to the organic systems, they show a lower flowability of the binder / aggregate mixture due to the high viscosity of the silicate. Additionally, when subjected to casting or casting temperatures of the metal, the silicates tend to melt making it difficult to remove the molten shapes from the castings by mechanical shaking methods. The molten conformations also lack water solubility which prevents their removal or dissolution by dispersion with water. A second inorganic system comprised of an aqueous solution of a polyphosphate glass was presented in WO 92/06808 which is incorporated herein by reference. These binders when cured show satisfactory strengths, excellent rehydration and breakage of the aggregate conformation after being exposed to the casting temperatures of the metal. The deficiencies of this binder system include: poor moisture resistance, softening of the aggregate system at high temperatures that restricts its use in ferrous alloy applications; and when compared to organic binders, low aggregate fluidity due to the relatively high levels of binder required for adequate strengths. A third inorganic system is known to be comprised of a main portion of a finely divided refractory material blended with a minor portion of a dry phosphate, to which a minor portion of an aqueous alkali metal silicate is subsequently added, as presented in FIG. U.S. Patent No. 2,895,838 (the complete disclosure of which is incorporated by reference) for preparing gas curable molds. This composition chemically reacts with a gaseous agent such as carbon dioxide, to cure the composition by reacting the phosphate with an alkali metal carbonate formed by curing the inorganic system with carbon dioxide. Another known inorganic binder system, which includes a combination of silicate and polyphosphate, is presented in the work of D.M. Kukuj et al, "Modification of Waterglass with Phosphorus Containing Inorganic Polymers" (whose complete presentation is incorporated as a reference). The method for preparing this binder includes the processing of the silicate and the polyphosphate at high temperatures and pressures in an autoclave to cause the chemical reaction of the inorganic polymers. The binder was then coated on sand and cured using CO2 at ambient temperatures. For this work, only a low level of polyphosphate could be incorporated in the preparation of the binder. In addition, Kukuj et al, found that the maximum resistance of the system had only 5% polyphosphate modifier and the resistance dropped dramatically when the binder contained more than 7% polyphosphate. Kukuj et al also found that small additions of polyphosphate in their binder (approximately 1 to 3%) caused a dramatic increase in binder viscosity before their addition to the aggregate. In this way, the deficiencies of this system include: high temperature and high pressure processing required to produce the binder, - the formation of new chemical compounds with high viscosity; and the low fluidity of the agglutinant / aggregate system. Also, like U.S. Patent No. 2,895,838, the chemical interaction of the binder system with a gas containing carbon dioxide was necessary to cure the system.

The gelation of the inorganic binders under appropriate conditions provides binding properties; however, unexpected gelation may occur prior to incorporation into the aggregate even if there are minor physical and / or chemical changes in the binder solution. This unintentional gelling, of course, is detrimental to the utility of the binder systems and has been witnessed in compositions of the present invention. The present inventors have conducted extensive studies in the silicate / phosphate systems and have achieved unexpected results in view of the results presented in U.S. Patent No. 2,895,838 and in that of Kukuj et al. The inventors of the present have also learned that gelation of the inorganic systems before addition to the aggregate is not inevitable. The inventors have found that if premature gelation occurs in the silicate / phosphate system of the present invention, the gelation condition can be overcome if agitation is used or if an aqueous addition is made or if the pH is adjusted upward. Taking these steps, the gelled composition will be a solution again.

SUMMARY OF THE INVENTION A principal objective of the invention is to provide novel inorganic binder systems as a substitute for the organic and inorganic binder systems known in the prior art. The new inorganic binder and aggregate systems have improved flowability (lower viscosity), improved moisture resistance and neither melt nor soften at high temperature, making it possible to use it with refractories and foundry sands to be used as foundry molds or hearts in contact with molten metal, including casting processes of ferrous metals. In addition, the problems associated with the undesirable gelling of the binders are avoided in the present invention. Moreover, the binder systems of the present invention produce good cold and hot tensile strength properties in aggregate conformations bonded with the binder of the present invention, even at low levels of binder. The binder systems of the present invention are not limited to narrow proportions of silica / soda or silicate / phosphate, but are effective in a wide range of proportions. The phosphates can be orthophosphates, condensed phosphates or mixtures thereof. The phosphates can be prepared in-house, in the presence of other ingredients, for example, silicate and / or aggregate, by the addition of a phosphoric acid and a base, for example, sodium hydroxide or converted from one phosphate to another in itself. by the addition of acid or base. An object of the present invention is to produce an inorganic binder system that when mixed with a particulate material can be used to prepare useful conformations with satisfactory handling and processing properties. Another object of the present invention is to produce an array of inorganic binder compositions containing silicates and phosphates which, when mixed with a particulate material, can be used to prepare useful conformations. Another object of the present invention is to produce an array of inorganic binder compositions essentially free of organic compounds. Another object of the invention is to produce an array of low viscosity binder compositions and to allow the dissolution of the premature gelling of these binder compositions. Another object of the invention is to produce a binder system containing phosphates for the casting of metals, for example, ferrous metals. Another object of the invention is to produce a binder system containing phosphates for molding non-ferrous metals and non-metallic compounds. Another object of the invention is to produce an array of binder compositions for aggregate conformations exhibiting good properties for shaking or disassembling in water, after exposure to the casting temperatures of the molten metal, for easy removal of the formed conformation. . Another object of the invention is to produce a binder that does not deform or soften significantly at temperatures below about 500 ° C Another object of the invention is to produce a binder composition that is heat curable. Therefore, additional objects of the invention are to provide methods of preparation and methods of using the novel binder systems of the invention to solve the problems associated with the prior art and form useful cured conformations, suitable as polymer and metal contact surfaces. melted, including casting and injection molds, casting molds, cores and mandrels. These and other objects of the invention will be apparent after considering the following descriptions and examples.

DETAILED DESCRIPTION OF THE INVENTION The present inventors have found that inorganic binder systems composed of silicates and phosphates are very versatile for binding particulate material during the manufacture of, for example, cores, molds, mandrels, wood particle boards, plastic compositions, briquettes and the agglutination of other forms to produce conformations with improved resistance to hot and cold tension. The inventors have found that in the inorganic binder system several variables can be adjusted so that a formulator can prepare or adapt a product to the needs of a customer. For example, the formulator can easily adjust the relative amounts of silicate and phosphate to change the properties of a particular shape that has formed. Additionally, the use of a specific phosphate or silicate can be selected by the formulation designer to obtain the desired results. In fact, the formulation designer using the invention can create binder systems that exhibit synergy with respect to the hot or cold tensile strengths of particle molds and cores. One can improve the mechanical and wet-shaking properties of the shaped shapes exposed to the temperatures of the molten metal using the binders of the invention instead of a binder containing 100% silicate. Furthermore, using the binder of the invention, the moisture resistance of molds and cores of particulate materials relative to all phosphate binders can be improved. These results can be obtained even with larger amounts of phosphate present in the binder system than the amounts presented in either U.S. Patent No. 2,895,838 or Kukuj et al. Furthermore, the compositions of the invention have the advantage of avoiding the use of the carbonates and the special gases containing carbon dioxide necessary for the production of these carbonates. The cured hearts and molds of the present invention also have the advantage of avoiding having an excess of water. This contrasts with the cured forms of the carbon dioxide curing process that contain an excess of water. This excess water is harmful when the conformation containing this excess is exposed to the casting temperatures of the metal. This often leads to low quality castings and restricts the use of cured conformations to simple configurations.

Silicates The silicates used in the binders of the invention can include various alkali metal silicates including potassium, sodium, cesium, rubidium and lithium. Other silicates such as ammonium silicates can be used. In general, the silicates are available commercially as solids or as aqueous solutions. Throughout this application, the silicates, as a component of the binder of the invention, are preferably aqueous alkaline solutions characterized by a solids content of about 45% by weight unless otherwise specified. Optionally, a solid silicate can be used. Soluble glass, that is, sodium silicate which is the preferred alkali metal silicate used in the binder of the invention, can be characterized by the general formula XSÍO2 and Na2 ?. The ratio of x and y, i.e., silica / alkali used in the present invention ranges from 0.6: 1 to 3.85: 1, preferably 1.1: 1 to 3.22: 1 and, more preferably from 1.1: 1 to 2.58: 1. Minor amounts of other elements such as alkaline earth metals, aluminum and the like may be present in varying proportions. The water content of the sodium silicate can vary depending on the properties, for example, the viscosity desired by the end user.

Phosphates The phosphates used in the binders of the invention include a salt of a phosphorus oxyacid which includes salts of phosphoric acids such as orthophosphoric acid, polyphosphoric acid, pyrophosphoric acid and metaphosphoric acid. The phosphate generally used is alkaline phosphate which includes both alkali metal phosphates and alkaline earth metal phosphates as well as ammonium phosphates. As used throughout the specification and claims, the term "phosphate" is intended to mean in the generic sense both crystalline and amorphous inorganic phosphates, for example, sodium phosphate glasses. Additionally, the phosphate is intended to include, but not be limited to, orthophosphates and condensed phosphates. Orthophosphates are compounds that have a monomeric tetrahedral ion unit (PO4) .3 Typical orthophosphates include sodium orthophosphates, for example, monosodium phosphate, disodium phosphate or trisodium phosphate, potassium orthophosphates and ammonium orthophosphates. which have more than one phosphorus atom, where the phosphorus atoms are not linked together, however, each phosphorus atom of the pair is directly linked to at least one same oxygen atom, for example, POP. of condensed phosphates in the present application includes linear polyphosphates, metaphosphates, pyrophosphates and ultraphosphates Metaphosphates are cyclic structures that include the ionic part ((P? 3) n) n ~, where n is at least 3, for example, (Nan (P? 3) n) Ultraphosphates are condensed phosphates in which at least some PO4 tetrahedra share 3 vertex oxygen atoms. in an ion (P2O2) ", for example, Nan H4-n (p2 ° 7) where n goes from 0 to 4. Linear polyphosphates have linear chains POP and include an ionic part of general formula ((? 3) nO), where n is the length of the chain ranging from 3 to several hundred, for example, 500, depending on the number of chain breakers, for example, H2O present. Commercial polyphosphate generally contains mixtures of linear polyphosphates and often also metaphosphates and are characterized by an average chain length ranging from at least 3, usually from 3 to about 45 and limited to 45 only by market demands, preferably the average varies from 3 to 32, more preferably from 4 to 21. A preferred category of polyphosphate is that of amorphous condensed phosphates, for example, water-soluble phosphate glasses. In view of the above teachings, one skilled in the art could produce mixtures of phosphates as defined above and still include small amounts (up to 10%) of modifying ions such as calcium, magnesium, zinc, aluminum, iron or boron in phosphates. soluble and produce a phosphate that is within the range of the present invention. In general, phosphates are comprised by the following formula for the molar ratio of oxide: (x M? + and M2 + z H20): P205 wherein Mi is selected from the group consisting of LÍ2O, Na2 ?, K2O, and (NH3) 2 '(H2?) and mixtures thereof. IY-2 is optional and is selected from the group consisting of CaO, MgO, ZnO, FeO, Fe203, A1203, B203. The total oxide ratio R = (x + y + z) / moles of P2O5 and varies from about 0.5 to 3.0 or greater, for example, 5. Typically, phosphates are classified by categories according to the value of R as shows below in Table A: It should be noted that the phosphates can be added directly to other ingredients, for example, added or silicates, or created in itself with the other ingredients. Creation in itself can be carried out using acids, for example, any of the phosphoric acids, or bases, for example, hydroxide or alkaline oxide. For example, phosphoric acid and sodium hydroxide could be added together or sequentially to prepare a phosphate in itself with other binding ingredients. The phosphates can still be converted into other phosphates by the addition of base or acid. For example, disodium phosphate can be converted to trisodium phosphate by the addition of sodium hydroxide, or converted to monosodium phosphate by the addition of phosphoric acid. The phosphates can be used in solid form or as aqueous solutions. The pH of the aqueous solutions can be acidic or alkaline. For condensed phosphates, the pH is related to factors such as the length of the phosphate chain.

Particulates The silicate / phosphate binder components can be used to mold conformations of water-insoluble particulate material consisting of, for example, plastics, earth, wood and preferably a refractory material such as silica, zircon, alumina, chromite, chamotte, olivine, silicon carbide, magnesite, dolomite, aluminum silicate, mulite, carbon, forsterite, chromite-magnesite and mixtures thereof. A preferred mold, core or mandrel for the formation of products for casting applications, for the casting of products of for example cast iron, brass, bronze, aluminum and other alloys and metals is produced from any of the sands identified above. . The molds, hearts and sand mandrels are well known to those of ordinary skill in the art.

Binder (composed of a silicate component and a phosphate component). The amount of a particular binder component (silicate or phosphate component) and the total amount of binder used to create a shaping, such as a mold, core or mandrel, depends on the strength requirements as well as the shaking requirements and / or dismountability in water of the conformation. The total weight percent of the binder, based on the weight of the particulate material used to form a conformation, is defined by the amount of solids present in the binder components combined unless otherwise specified. In the present invention, the weight percent solids of the binder, based on the weight of the particulate material is preferably 0.4-5.0% and more preferably 0.4-2.5% and more preferably 0.6-1.6%. The ratio of silicate / phosphate in the binder formed of a silicate component and a phosphate component of the invention is from 97.5: 2.5 to 5:95; preferably from 95: 5 to 25:75 and more preferably 90:10 to 50:50. The proportions within the range of 39: 1 to 31: 1 and from 1: 2 to 1:19 are also of particular interest. The silicate and phosphate components are mixed and in no way subjected to high temperatures before mixing the binder with the aggregate. By high temperature it refers to temperatures above about 90 ° C. Preferably, the binders are mixed at room temperature or near ambient.

Additives The additives are used in special cases for special requirements. The binder systems of the invention may include a wide variety of additional materials. These materials may include alkali hydroxides, for example, NaOH, water and various organic and inorganic additives. NaOH (eg, 45% -50% solutions) may be present in the binder of the invention in amounts of up to 10% -40% by weight (solutions). Additional water may be present in amounts of 0% -15% of the binder by weight. Preferably, the aqueous binders of the present invention contain water in an amount from about 30 to about 80% by weight of the binder. Lesser amounts of other additives such as surfactants may be present. The surfactants may be anionic, nonionic, amphoteric cationic or mixtures thereof. Examples of water-soluble surfactants are the anionic surfactants selected from organic sulfates, organic sulfonates and organic ester phosphates, for example, potassium 2-ethylhexyl phosphate. Certain surfactants also operate as flow control agents. A typical flow control agent includes an agent sold under the trade name PA 800K, more fully defined as potassium 2-ethylhexyl phosphate, which is commercially available from LAKELAND LABORATORIES Ltd., Manchester, England. Other flow control agents include 2-ethylhexyl acid phosphate, the anionic / non-ionic surfactant DISPERSE-AYD W28 sold by Daniel Products, 400 Claremont Avenue, Jersey City, NJ. E.U.A., and DISPEX N40V, a sodium salt of a polyacrylate sold by Allied Colloids, Suffolk, VA, E.U.A. Other additives include moisture resistant additives, removability (or breakdown) enhancers, preservatives, inks, bulking agents, additives for hot strength or flow improvers. Moisture resistant additives include potassium tetraborate, zinc carbonate, zinc oxide. The removability (or breakdown) improvers include sugar, for example, sucrose, dextrin and sawdust. Still other additives include release agents, adhesion promoters for example, silanes, additives to improve metal casting, for example, red iron oxide, black iron oxide or clay, etc. Refractory coatings can be used to improve the finish of the laundry. Of course, the additives may be added alone or in combination.

Mixing of the Binder and. The Particulate The process for mixing the binder with the water insoluble particulate may include the modification, if necessary, of the ratio of silica / sodium silicate soda by treating the sodium silicate with alkali. In general, an alkaline aqueous solution of sodium silicate having an appropriate ratio of silica to soda is added to a foundry aggregate by pouring the solution into the mixer. Next, the aqueous phosphate is added and mixed, and optionally a flow agent is added followed by further mixing. Alternatively, a solid phosphate component may be included in the particulate, which is first mixed with water and then an alkaline aqueous sodium silicate solution is added thereto. This composition blends perfectly. In a further alternative, the silicate and phosphate components can be premixed together to form an aqueous solution and stored even in this condition before being added to the sand. At least in some embodiments, the premixed solution is a clear (transparent) mixture at least before mixing it with the aggregate.

In another alternative, the silicate, phosphate and aggregate components can be mixed dry and stored in that condition. When they are ready, water can be added to this mixture. As an alternative to provide the phosphate as a separate ingredient, this can be formed in itself by adding phosphoric acid and a base as binder ingredients before or after mixing with the aggregate or the silicate. Moreover, the phosphate in the binder can be changed in itself into a different phosphate by the addition of acid or base. After the binder and particulate are mixed, the mixture is loaded in a pattern to form a conformation and the shaping is cured. The curing is effected by dehydrating the conformation generally by the expulsion of the free water. Preferably, the shaping is dehydrated to less than 1% water by weight by blowing inert gas through the shaping, applying vacuum through the shaping and / or heating. As used throughout the specification and in the claims, the term "mold" is taken in a generic sense to refer to casting configurations that include both the molds and the hearts, this invention is in no way limited to the former. Moreover, "mold" is intended to include various patterns for use in the molding technique including casting and injection molds, as well as shell molds including shell forming elements in addition to a finished shell mold structure prepared by the assembly of two or more complementary elements of thin-walled shell mold. From here, it will be appreciated that the term "mold" is used to include a shape or surface that generally defines a cast and, specifically, includes molds, hearts and mandrels. The invention may be further illustrated with reference to the non-limiting examples as set forth below: Process of Held Cane Helps with Air General Procedure A binder that contains an aqueous solution of sodium silicate that has a ratio of Si? 2 / Na2? of 3.22, that is, the commercially available OXYCHEM and sold under the designation "Grade 42" (it has a solids content of 38.3%) and / or an aqueous polyphosphate solution that has an average chain length of 21, where the silicate and / or the phosphate were present as shown in Table 1 were added to the sand as follows: 3000 gm of silica sand WEDRON 530 were placed in a Hobart mixing bowl. In the sand depressions were made. In the separated depressions, appropriate amounts (see Table 1) of aqueous sodium silicate and / or sodium polyphosphate (1.57% total solids at binder level, based on sand) were placed. The mixer was ripped off and mixing continued for 2 minutes. Care was taken to ensure uniform mixing of the binder components. The coated sand was then blown at 85 psi air pressure for 1 second in a box of three-cavity dog bone hearts., which was equilibrated at 105 ° C ± 5 °, using a Heart Redford Cartridge Blower (Redford Iron and Equipment Company, Detroit, MI). Curing was carried out by blowing air at 120 ° C ± 5 ° through the heart box at 30 psi for 60 seconds. Using the previous methodology, additional sets of dog bones were made from the same sand. In this regard, the sand is mixed and tested to determine the average values of hot tensile strength (Table 1), the resistance to the cold tension (Table 2), the resistance retained after 15 minutes of treatment at 925 ° C (Table 6), and the time for softening with water after 15 minutes of treatment at 925 ° C (Table 7). The Example numbers in Table 1 should also be used in association with Tables 2, 6 and 7. The values reported in the Tables below are generally averages of at least three measurements.

Example 1 (Comparison) This example used the above procedure with the aqueous solution of sodium silicate having a proportion of Si? 2 / a2? of 3.22, that is, the one commercially available from OXYCHEM and sold under the designation "Grade 42" (which has a solids content of 38.3%).

Examples 2-9 The procedure described above was repeated, wherein the weight ratio of silicate to phosphate varied as shown in the first row of Table 1 below.

EXAMPLE 10 (Comparison) The general procedure described above was repeated using 100% phosphate binder (see the right-most column of the silicate-to-phosphate weight ratio data of Table 1 below).

Examples 12-19, 22-29 and. 32-39 The procedure of Example 2 was repeated, with the exception that in all cases a commercially available sodium silicate with a Si 2 / Na 2 ratio was used. 2.58, and for examples 12-19 a polyphosphate having an average chain length of 32 was used; for examples 22-29 an average chain length of 21 was used and for Examples 32-39 an average chain length of 7 was used. All Examples starting from Example 12 were completed with 45% silicate solutions in weight and with 45% by weight phosphate solutions.

Examples Pairs 11,20; 21.30 y. 31.40 (Comparison) The comparative examples, shown in the far left and right columns of the silicate to phosphate weight ratio data of Table 1 were prepared containing in the first case (ie, in Examples 11). , 21 and 31) 100% sodium silicate with proportions of Si? 2 / Na2? of 2.58, and in the second case (ie, in Examples 20, 30 and 40) 100% polyphosphate with average chain lengths of 32, 21 and 7, respectively.

And emplos 42-49, 52-59 y. 62-69 These examples were prepared as in Example 2, with the exception that a silicate having a SiO / NanO do ratio was used? .00 (which is commercially available) and the average length of the polyphosphate chain varied according to 32, 21, 7 as above.

Examples Pairs 41.50; 51.60 y_ 61.70 (Comparison) The comparative examples shown in the far left and right columns of the silicate-to-phosphate weight ratio data of Table 1 were prepared and contained in the first case (i.e. Examples 41, 51 and 61) 100% sodium silicate with proportions of Si? 2 / Na2? of 2.00 and in the second case (ie, in Examples 50, 60 and 70) 100% polyphosphate with average chain lengths of 32, 21 and 7.

Examples 72-79, 82-89 and 92-99 These examples were obtained as described in Example 2 above, with the exception that a sodium silicate with a Si 2 / Na 2 ratio was used. of 1.60 and the average chain length of the polyphosphate varied as shown in Table 1. A silicate having a SiO2 / Na2 ratio. of 1.60 is not commercially available but can be produced by adding 22.06 grams of 45% NaOH to 100 grams of an aqueous sodium silicate having a proportion of Si? 2 / Na2? of 2.58.

Examples Pairs 71.80; 81, 90 and 91,100 (Comparison) The comparative examples shown in the far left and right columns of the silicate to phosphate weight ratio data of Table 1 were prepared and contained in the first case (Examples 71, 81 and 91) 100% sodium silicate with proportions of Si? 2 / Na2? of 1.60, and in the second case (Examples 80, 90 and 100) 100% polyphosphates with average chain lengths of 32, 21 and 7.

Examples 102-109, 112-119 and 123-130 The procedure for obtaining these examples was repeated as set forth in Example 2 above, with the exception that a sodium silicate having a SiO2 / Na2 ratio was used. of 1.30 and that is not commercially available. And that can however be produced by adding 35.49 grams of 45% NaOH to 100 grams of an aqueous sodium silicate having a Si2 / Na2 ratio? of 2.58.

Examples Pairs 101, 110; 111, 120 and. 121, 130 (Comparison) The comparative examples shown in the far left and right columns of the silicate to phosphate weight ratio data of Table 1 were prepared and contained in the first case (Examples 101, 111 and 121). ) 100% sodium silicate with proportions of Si? 2 / Na2? of 1.30 and in the second case (Examples 110, 120 and 130) 100% phosphates with average chain lengths of 32, 21 and 7.

Examples 132-139, 142-149 and 152-159 The procedure for obtaining these examples was repeated as set forth in the aforementioned Example 2, with the exception that a silicate having a proportion of Si 2 / Na 2? of 1.00 and that is not available commercially. However, it can be produced by adding 56.95 grams of 45% NaOH to 100 grams of an aqueous sodium silicate having a proportion of Si? 2 / a2? of 2.58.

Examples Pairs 131,140; 141,150 and 151,160 The comparative examples shown in the far left and right columns of the silicate to phosphate weight ratio data of Table 1 were prepared and contained in the first case (Examples 131, 141 and 151) 100% of sodium silicate with proportions of Si? 2 / Na2? of 1.00 and in the second case (Examples 140, 150 and 160) 100% phosphates with average chain lengths of 32, 21 and 7. or The following key should be used in association with Tables 1, 2, 6, 7, 15, 16, 17 and 18. a. This sodium silicate is obtained commercially as a solution at 38.3% solids. The level of binder used was adjusted so that the same level of solids was used in other experiments. b. A liquid sodium silicate with this ratio of SÍO2 to Na2? It is not commercially available. However, the ratio of SÍO2 to Na2? was adjusted by adding the appropriate amounts of 45% NaOH to a silicate with a ratio of 2.58. c. Averages of two experiments are reported. d. Under the experimental conditions it was difficult to prepare dog bones. In severe cases, no dog bone was prepared successfully. When the box of hearts was opened, the dog bones were broken. However, there is evidence that the binder was cured under these conditions. Note l: When empty spaces appear in Tables 1, 2, 6, 7 and 15-18, this indicates that the experiment was not run. In this way, no dog bone was produced. For example, Example 72 is a ghost example, no dog bone was produced. Note 2: In all the Tables and in some other place ND means "not determined".

Resistance to Hot and Cold Tension After curing, the heart box opened and the dog bones were removed. A dog bone was used for the immediate determination of the tensile strength (hot) (Table 1 above). All stress resistance measurements were made with an Electronic Voltage Tester Model ZGII-XS (Thwing-Albert Instrument Company, Philadelphia, PA). As used throughout the specification and in the claims the "hot" tensile strength refers to the strength of the shape as it is "separated" from its pattern and the "cold" tensile strength refers to the Resistance 30 minutes after stripping to the shape of your pattern. Hot and cold tensile strength properties are critical when developing a commercial binder system. It is essential that the hearts and molds made with these binders have sufficient strength to be manipulated during the making and handling of the heart and the mold. As shown in Table 1, synergistic results of hot tensile strength are obtained using a binder combination of sodium silicate and sodium polyphosphate against binders containing either 100% sodium silicate or binders containing 100% phosphate. These results can be manipulated as shown in Table 1 by adjusting the ratio of Si? 2 / Na2? of the sodium silicate binder varying the average chain length of the phosphate component or changing the weight ratio of the silicate component / phosphate component. As shown, the maximum hot stresses in these series of non-limiting examples were obtained for Examples 33 and 34, respectively, (151 psi and 163 psi, respectively), using a sodium silicate component having a Si? 2 / ratio a2? 2.58, a polyphosphate component having an average chain length of 7 and weight ratio of sodium silicate binder component: polyphosphate binder component of 83.3: 16.7 (Example 33) and 75:25 (Example 34) . In general, for a sodium silicate given in the combination of binder systems of the invention, the impact of sodium polyphosphates on the hot tensile strength was relatively small when compared to the same silicate level. This is the best shown in the series of silicate experiments of 2.58 and 2.00. On the other hand, sodium silicate is essential to obtain good hot resistances from the systems. While the combination of binders with the silicate of proportion 2.S8 appeared to have the highest total hot strength, there are some binding systems with silicates of proportions 3.22 and 2.00 that produce hot resistances that approximate those with a silicate of 2.58 ratio. It should be noted that the addition of sodium polyphosphates in low proportion silicates (proportion <2.0) allowed the preparation of dog bones in some examples shown in Table 1. The two remaining dog bones were used to determine the cold tensile strength (Table 2) and the weight of the dog bone. Resistance to cold stress and the weight of the dog bone were measured after the dog bones were cooled for 30 minutes. Weight comparisons of dog bones (not shown in the Tables) provide a good gauge of the fluidity of the binder / aggregate systems. Heavier dog bones indicate better fluency. In general, dog bones prepared from 100% silicate binders weighed less than dog bones prepared with silicate / phosphate binders. These results indicate that the aggregate or particulate materials coated with the binder combination of the invention have improved flow properties. Sf-q? 'M i; In Table 2, synergistic results of the cold tensile strength are obtained using a combination binder of sodium silicate and polyphosphate (see especially Examples 43, 44, 52, 53, 54 and 64). against binders that contain either 100% sodium silicate or binders that contain 100% phosphate. These results can be manipulated in an additional way, as shown in Table 2, by adjusting the proportion of Si? 2 / Na2? of the liquid sodium silicate component, varying the length of the polyphosphate component chain or changing the weight ratio of the silicate component / polyphosphate component. In general, Table 2 also shows that dog bones produced with sodium silicates having ratios of 2.58 and 2.00 of Si? 2 / Na2? They exhibit the highest total cold stress and with the broadest range of silicate to polyphosphate ratio have good resistance to cold stress. It is important to note that, for low proportion silicates (proportion <2.0), the addition of polyphosphate allows the preparation of dog bones shown in Table 2. 1 C fifteen twenty Effect of Using Various Phosphates The phosphate component of the binder can be prepared from a variety of phosphates as previously reported. In general, phosphates have an average chain length value of n, n is the average number of phosphate groups in the chain. Table 3 exemplifies the variety of phosphates usable in the present invention. As shown in Table 3, the binder compositions containing phosphate chains wherein n = 1, 2, 3, 4 and 21 were used to make dog bones. The phosphates were dissolved in water to give 45% (by weight) solutions in most examples. If 45% solutions could not be prepared, saturated phosphate solutions were prepared and adjustments were made to account for differences in solids. It was observed that sodium tripolyphosphate is not very soluble in water. It could only be prepared at 14% (by weight of solution). To maintain a silicate to phosphate ratio consistent with the other binders in Table 3, additional sodium tripolyphosphate solution was added to the binder. The components of the binder mixed with the sand were loaded into a heart box of three dog bones and cured by expelling the water. The dog bones with the binder combination of the invention were successfully produced using the various phosphate compounds as listed in the heading of Table 3. ? 0 The following key is associated with Table 3. a. The sodium silicate has a weight ratio of SÍO2 to Na2Ü of 2.58. BOS is defined as weight based on the weight of sand. b. The phosphates were dissolved in water to provide 45% (by weight) solutions. If 45% solutions could not be prepared, saturated phosphate solutions were prepared and adjustments made to explain the difference in solids. c. Average of two tests. d. Sodium tripolyphosphate is not very soluble in water. It could only be prepared at 14% (by weight of solution). To maintain the ratio of silicate to phosphate, additional water was present in the binder. A longer curing time (90 seconds) was used to completely remove the water during curing. and. VITRAFOS is a sodium polyphosphate available from Rhéne-Poulene Basic Chemicals Co., Shelton, CT. F. BUIDA 9 is a sodium polyphosphate available from Cometáis, Inc., New York, NY.

Gelification When Silicates are Mixed and. Phosphates As discussed above, unexpected gelation can occur in these inorganic systems even if there are only minor physical and / or chemical changes in the solution. The premature or undesirable gelling of the inorganic polymers before their addition to the aggregate or particulate is detrimental to the utility of the binder systems. Experiments were conducted to study the propensity of gelation of the binder system of the invention. Sodium silicates and polyphosphates were mixed in various proportions. Observations were made as they were mixed. The results are shown in Table 4.

In all cases, when sodium silicates (with proportions of 2.00 and 2.58) and sodium polyphosphates (average chain length = 1, 21 and 32) were mixed, a gel was formed as these materials came in contact with one another. For mixtures in which the sodium silicate component with a ratio of 2.58 accounted for more than 30% (by weight) of the total mixture, the gel was dissolved with stirring (i.e., clear solutions were obtained). Normally, the gel dissolved in less than one hour. As the gel dissolved, a small amount of spongy particles was normally observed in the solution. For mixtures containing 30% by weight or less of the sodium silicate with a ratio of 2.58, the gel was not affected by agitation for an extended period (38 hours). By contrast, for sodium silicate with a ratio of 2.00, the gel formed by combining 30% sodium silicate with 70% polyphosphate (by weight) was dissolved with stirring, suggesting a higher solubility of the gel in liquid silicates more alkaline Another important observation is that all the gels were easily dissolved with the addition of water, alkali hydroxide and / or ammonium hydroxide. The dissolution of the gel by addition of water and / or sodium hydroxide is shown in Table 5 The gels were formed by combining sodium silicate at 75? > by weight (silica / soda ratio of 2.58) and 25 weight percent of VTTRAFOS (45% solution).

As shown in Table 5, the sodium hydroxide solutions were very effective in dissolving the gels produced by the formation of a silicate and polyphosphate binder combination. Of course, other alkalies such as KOH, NH 4 OH, LiOH, etc. may be used. The water alone was also effective in dissolving the gels; however, a large amount of water was required to dissolve these gels.

Fluidity The binder combination of the present invention has a reduced viscosity as shown in the physical properties of Table 5A. When the binder of reduced viscosity is mixed with the aggregate, it will impart an improved flow to the mixture. This allows the flow in molds in an intricate way. If desired, the fluidity can be further improved by the addition of flow improvers and / or flow control agents. In Table 5A, BOR means the weight based on the resin weight. a - The weight ratio of silica to soda is 2.58. b - The phosphate component is a 45"solution, the phosphate is VITRAOS that has a chain length of 21. c - The ratio of silica to soda is 2.0 Shake A main disadvantage of the sodium silicate binder are its poor properties of mechanical shaking or hot and cold disassembling During the casting process, when the temperatures of cores and molds reach temperatures above 700 ° C, the sodium silicate is thermally transformed into a vitreous matrix and this gives Mechanical shaking is usually done by vibrating or impacting the cast metal that combines with the heart, in fact, a difficult mechanical shaking can cause stresses in the cast metal, in these cases, it is necessary to treat or recose the casting to recover the properties of the metal, in these cases, it is necessary to heat, treat or recoser to the casting to recover the malleability of the metal.

The dismoatability of the 100% silicate binder is also difficult due to the insolubility of the vitreous silicate matrix formed by the exposure of a mold or core to the temperatures of the molten metal. In the invention, a fluid such as water can be used to dismantle the heart and drag the refractory sands for recovery and reuse. The phosphates alone also exhibit poor cold and hot mechanical shaking properties after exposure to pouring temperatures. The data in Table 6 show that the dog bones produced with the combination of binders of the invention and subjected to temperatures of 925 ° C in a muffle furnace for fifteen minutes, have a much more favorable detachability and shaking properties (resistance to the lesser retained tension as tested in a Thwing Albert Tester), that the shaking properties of dog bones produced with 100% of a single binder component (100% silicate or 100% phosphate). Of course, the more favorable the mechanical shaking properties, the less likely metalworking will be damaged. In view of the foregoing, the binders of the invention are recommended for the production of cast metals, especially ferrous castings. fifteen Table 7 represents the softening and thus, the recovery properties of the binder systems of the invention when water is used as an agent to recover the aggregate. The reported results suggest that many of the binder combinations can be dispersed with water more easily than systems with single binders of sodium silicate and polyphosphate. The faster softening of the binder combination suggests easier removal of spent binder in the aggregate. Of course this translates into benefits for the recovery of the aggregate. ¿00 fifteen twenty Hydroxides other than sodium hydroxide can be used successfully to modify the sodium silicates. Table 8 below shows that the potassium and ammonium hydroxides can be used successfully in the applications of the invention. Mixtures of these hydroxides can also be used.

The binder combination used in the previous series of experiments was composed of a silicate with a weight ratio of SIO2 to Na2? of 2.58 and VITRAFOS polyphosphate with an average chain length of 21. In these sand tests, the binder level was 3.5% by weight BOS or 1.575% by weight of BOS solids. The weight ratio of silicate to phosphate was 3: 1. The potassium silicate can replace the sodium silicates in the binder systems of the invention. Potassium silicates can also be used in conjunction with sodium silicates as a first component of a binder system. Table 9 below illustrates the above.

The potassium silicates used in the above experiments was KASIL # 6, available from PQ Corp., Philadelphia, PA. The silicate has a ratio of SIO2 to K2O of 2.1. A sodium silicate with a weight ratio of SiO2 to Na2? of 2.58.

Reblancing of the Combination of Binders at High Temperatures. Specimens prepared with 100% sodium polyphosphate aqueous binder systems tend to soften when heated to temperatures near 250 ° C. If a heart and / or a mold soften at the elevated temperatures experienced during the metal casting processes, serious casting defects will result. Comparative tests were conducted to determine if any softening occurs with the binder combination system of the invention at 500 ° C. Softening at 500 ° C was measured as follows: A dog bone was supported at both ends and a weight of 200 grams was hung at the midpoint. The apparatus was then placed in an oven at 500 ° C. The time at which the dog bone broke was recorded. The results of the test are shown in Table 10. 2. The sodium silicate used in this was the? B 41, which has a silica / soda ratio of 2.65. Ul r-. 3UDIT 4, 7, 8 and S are sodium phosphates with different ostensible chain lengths from Cometáis, Inc., Ne York, NY. : ALUSIL ET is an aluminum and sodium silicate and is used as an additive for resistance in alley. - :. PA 800K is a phosphate of 2-et? Lhex? Lpotas? O and was used as a flow agent available from Lakeland Laboratories Ltd., Manchester, England. and. Mixture of SB 41 with sucrose. F. Polyphosphate solutions at 45 * by weight were used. 10 g. Polyphosphate powder was used.

The whole phosphate system broke rapidly (21 seconds) when the specimen was placed in the oven at 500 ° C. In fact, no softening of the binder combination was observed at temperatures up to 500 ° C. The all-sodium silicate binder also did not soften at temperatures up to 500 ° C.

Application of the Binder Combination There are several ways in which combinations of sodium silicate binders and phosphate binders can be applied. A part of the binder system is preferred. Providing customers with products that contain both the silicate and phosphate systems will simplify the handling and storage requirements in foundry operations. However, this requires the premixing of phosphates either as liquids or as a solid in a liquid or as a mixture of two solids. Alternatively, the use of two-component systems is possible. It is feasible to supply the separated silicate and phosphate as liquid components. Additionally, a multicomponent binder system can be formulated with liquid sodium silicate, solid polyphosphate and water (or hydroxide) as individual ingredients. The individual components can be added to the foundry sand simultaneously (or in sequence) to provide a curable sand mixture. The modes of the selected component were evaluated and the data is shown in Table 11.

LD.

The weight ratio of SiO; to Na20 is 2.58 The data in Table 11 shows that all these methods of applying the binder combination system can be used successfully.

Aging of the Binder Combination As previously stated, the one-part binder system is preferred for ease of use. The binder from one part was prepared, and subjected to accelerated aging at 40 ° C. The aged binder was mixed with the aggregate and used to prepare dog bones. The results are shown in Table 12. to. The binder combination contained 3 parts of SB 41, a part of 50% NaOH, a part of water and parts of BUDIT 7 (45 V solution by weight). 47, the binder was coated on CONGLETON 60 sand. B. The curing was carried out by blowing air at 140 ° -150 ° C for 60 seconds with the heart box at 120 ° C. c. The time for rupture at 500 ° C was measured as reported in Table 10.

The hot tensile and softening properties of the hearts produced with this binder combination did not change significantly during 28 days, suggesting that the binder composition of one part did not age appreciably at 40 ° C until between 28 and 35 days .

Use of Other Silicates High-ratio sodium silicate (ratio of 3.85) and lithium silicate were evaluated in the binder combination. These silicates are available from Crosfield Chemicals (Arrington, England). Several formulations were prepared and tested. The results are shown in Table 13.

L? oo fifteen to. This sodium silicate CRYSTAL 52, available from Crosfield Chemicals, Arrington, England. b. Lithium silicate CRYSTAL L40, available from Crosfield Chemicals, Warrington, England, Si02 / Li20 = 8.8. c. This SB 41 sodium silicate, available from Crosfield Chemicals, Warrington, England, d. Dust. The data in Table 13 indicates that a silicate with a ratio of 3.85 and a lithium silicate can be used successfully as silicate. No significant difference in performance was found.

Effect of Sand on the Combination of Binder Some casting binders are very sensitive to the type of sand and can fail miserably if unacceptable sand is used. The following tests were conducted with several sands to determine the effect of sand type on the tensile strength. The data are shown in Table 1. to. Sand test procedure: the binder was added to the sand and mixed for 2 minutes with a KENWOOD CHEF mixer. Using a blow machine, the coated sand was blown in a box of dog bone hearts at 120 ° C and cured with a hot air purge (140-150 ° C) at 50 psi pressure and a flow of 5 liters / second for 60 seconds. The tensile strengths were measured using a universal RIDSDALE sand resistance machine. b. Number of fineness of the grain of the American Foundrymans Society. The data in Table 14 show that the binder combination of the invention can be used with a wide range of sands, including silica, zircon, chromite and olivine.

Process of Warmed Box In a similar way to the experiments conducted previously for the process of heated box aided with air, these tests were designed to determine but do not define the range of use of the binder combination. The general procedure for testing the sand for the heated box process is as follows: the binders used in these experiments contained 45.0 + 0.5% solids, unless otherwise specified. 3000 gm of silica sand WEDRON 530 were placed in a Hobart mixing bowl. Two depressions were made in the sand. Appropriate amounts of sodium silicate and sodium phosphate (see Table 15) (3.5% total binder level, based on the weight of the sand) were placed in the separate depressions. The mixer was ripped off and mixing continued for 2 minutes. Care was taken to ensure even mixing of the binder components. The coated sand was then blown at 85 psi air pressure for 1 second in a box of hearts for 3 dog bones, which was equilibrated at 218 ° C, using a Heart Redford Cartridge Blower (Redford Iron and Equipment Company, Detroit, MI). After 60 seconds, the heart box was opened and the dog bones were removed. A dog bone was used for the immediate determination of the tensile strength (hot). The two remaining dog bones were used to test dog bone weight and cold stress. The cold tension was measured after the dog bones were cooled for 30 minutes. The averages of at least 3 measurements were reported. Additional dog bones were prepared to test the moisture resistance, the retained tensile strength and the softening in water after exposure to the metal casting temperature (925 ° C).

Resistance to Hot Tension Table 15 shows the variations of the hot tensile strengths with respect to the composition of the binder composition.

Note: See Table 1 for the footnotes of Tables 15-1E Under the experimental conditions, the systems of all sodium silicate with sodium silicates with proportions of 3.22, 2.58 and 2.00 were cured to have sufficient resistances to prepare dog bones. The addition of sodium phosphate resulted in a higher hot stress for the systems of the binder combination. The cold tensile strengths of Table 16 show that dog bones produced with Si? 2 / a2Ü ratios of 2.58 and 2.00 had the highest total cold stress. These results are consistent with those reported in Table 2. With silicates of other proportions, the resistance to cold stress is slightly lower. However, molds produced with the combination of binders at other proportions are strong enough for common casting practices. It is important to note that sodium silicates with minor proportion, dog bones could not be made with sodium silicate alone. The addition of phosphate made it possible to prepare dog bones and the resistance data suggested that these binder systems are practical in casting applications. yes Table 17 represents the retained tensile strengths of the binder combination systems after exposure to 925 ° C in a muffle furnace for 15 minutes.

The data in Table 17 strongly suggest that the binder systems of the invention had much more favorable mechanical shaking properties than all silicate binders. These data are consistent with the data of Table 6. Table 18 represents the softening properties and, thus, the recovery properties of the binder systems of the invention using water. The data are consistent with those reported in Table 7.

The results suggest that many of the binders in the combination require their solubility and could dissolve with water much more easily than systems with sodium silicate binders alone. The dog bones produced with the. combination of binders with high silicate levels (> 90%) were more resistant to softening with water. As explained above, this is probably due to the formation of "vitreous silicate" during exposure to elevated temperatures. The faster softening of the binders in the combination suggest an easier removal or removal of the spent binder from the sand. These results again translate into a benefit for sand recovery. A wet shake and an improved sand recovery are clearly other advantages of the combination binders. These results are consistent with the results reported in Table 7. With a composition of binder composition having 75% by weight of sodium silicate with a ratio of 2.58 and 25% by weight of sodium phosphate VITRAFOS (45% solution in weight), the effect of various levels of binder was investigated. The results are shown in Table 19.

As expected, the results show that at higher binder levels the tensile properties and the scratch hardness are increased. However, within the range of binder level studied, the binders of the combination, after exposure to 925 ° C, were very low in the resistances to the retained tension and could soften in water very quickly.

The curing conditions were also examined. Again with a binder combination composition having 75% by weight of sodium silicate with a proportion of 2.58 and 25% by weight of sodium phosphate VITRAFOS (45% by weight solution), different box temperatures were evaluated for curing and resting times. Tension strengths (cold and hot), scratch hardness and retained strength after high humidity storage were monitored and the results are shown in Table 20.

The data in Table 20 show that the hot tensile strength increased in general with a higher case temperature and a longer dwell time. For box temperatures at 177 ° and 218 ° C, longer dwell times did not have a greater impact on the cold tensile strength. A very interesting observation is the resistances retained after exposure to high humidity. Curing at a higher box temperature and a longer resting time made the cured dog bones less susceptible to moisture. As discussed in the above procedure, an air purge was not used in the heated box process. Because the binder combination system generates a large amount of water vapor during the curing process, an air purge (to remove water vapor more effectively) was incorporated in this series of experiments during the cycle of Cured to determine the benefits, if any, on curing. The data is shown in Table 21. 1. The binder includes 75Y, by weight of a sodium silicate with a proportion of 2.58 and 25% by weight of VITRAOS (45% by weight solution). The total level of binders was 3.5%, based on weight and sand. WEDRON 530 silica sand obtained from edron Silica Co., Wedron, Illinois was used. 2. Ambient air was introduced into the heart box at 30 psi. With a short-lived ambient air purge, improvements were observed in the cold tension resistance. However, hot tension and scratch hardness were little cted. As an alternative to the air purge, vacuum can be drawn through the form to aid dehydration of the form. The effect of incorporating borate ions in the binder combination was studied. Potassium tetraborate tetrahydrate was dissolved in water to obtain a 10 wt% solution. The solubility of potassium tetraborate in water is limited. This solution was added to the sand as the binder components were added. The resulting sand mixture was evaluated. The results are shown in Table 22 1. Using a potassium tetraborate tetrahydrate, a 10 wt% solution was prepared. This solution was added to the sand mixture as the binder components were added. The curing was carried out by heating the coated sand in a pattern at 218 ° C for 60 seconds. The data in Table 22 show that the addition of potassium tetraborate caused a drop in cold tensile strength. However, and most significantly, the system containing potassium tetraborate was more resistant to moisture. It is also important to note that mechanical shaking properties (dry and wet) were not cted by the addition of tetraborate. From all the above data, it is evident that a binder and a method for improving the characteristics of an inorganic mold for use in casting, as well as in the fields of forming, casting and molding have been provided in accordance with the present invention. of products, such as injection molding, polymer casting, concrete casting, etc. The molds of the present invention are superior when the surface of the mold has recesses or other shape that prevents separation of the mold and the article. The improved disassembly of the molds and cores of the present invention facilitates this use each time separation of the article is a problem. While the invention has been described in conjunction with the specific embodiments thereof and with reference to the Tables presented therein, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the above description. . For example, the methods of the invention require dehydration of the shaped aggregate to cure the shaping. The description of dehydration has included heating and purging with hot air. Dehydration under vacuum could also be used. Nevertheless, it will be understood that for the purposes of this specification, air is considered an inert gas and could be replaced with any other inert gas, such as hydrogen, argon, etc. or mixtures of inert gases. The temperature of the air or other inert gas is such that the dehydration is effected and adequate results have been obtained at a temperature of 90 ° C and above. The inert gas can be used to effect only dehydration or it can be used in combination with the heated box mode. In some situations, ambient air or other inert gas may be used rather than hot air or other inert gas. Thus, vacuum aid can also be used alone or in combination with the other modalities to facilitate dehydration. In accordance with the foregoing, it is intended that the present invention include all of these alternatives, modifications and variations as set forth and which are within the spirit and scope of the appended claims.

Claims (58)

CLAIMS;

1. A binder composition characterized in that it comprises: (a) an unreacted mixture of a silicate and a phosphate in an aqueous medium; (b) where the resulting mixture is a solution.

2. The binder composition of claim 1, characterized in that the silicate is at least one selected from the group consisting of alkali metal silicates and ammonium silicates.

3. The binder composition of claim 1, characterized in that the phosphate is at least one which is selected from the group consisting of alkali metal phosphates and ammonium phosphates.

4. The binder composition of claim 1, characterized in that the silicate comprises sodium silicate and the phosphate is at least one polyphosphate selected from the group consisting of sodium polyphosphate and potassium polyphosphate.

5. The binder composition of claim 4, characterized in that the polyphosphate has an ionic part with formula ((P? 3> nO) where n is the average length of the chain and is between 3 and 32, inclusive.

The binder composition of claim 1, characterized in that it further comprises a surfactant

7. The binder composition of claim 1, characterized in that it further comprises a water-soluble anionic surfactant selected from the group consisting of organic sulfates, organic sulfonates, esters of organic phosphate and mixtures thereof

8. A heat-curable binder composition characterized in that it comprises a water-soluble silicate and a water-soluble phosphate in an aqueous medium, wherein the water content of the composition is such that the The composition is heat curable

9. The heat-curable binder composition of claim 8, characterized in that the water content is it is from about 30% by weight to about 80% by weight of the binder composition.

10. The binder composition of claim 8, characterized in that the silicate: phosphate ratio is from about 39: 1 to about 1:19 by weight based on the solids.

11. The binder composition of claim 10, characterized in that the silicate: phosphate ratio is from about 39: 1 to 31: 1 by weight based on the solids.

12. The binder composition of claim 10, characterized in that the silicate: phosphate ratio is from about 1: 2 to 1:19 based on the solids.

13. A unreacted and uncured binder composition for binding particulate material characterized in that it comprises a mixture of an inorganic silicate and an inorganic phosphate, wherein the mixture is not subjected to high temperatures before mixing the mixture with the particulate material.

14. A composition characterized in that it comprises a dry silicate component, a dry particulate component and a dry phosphate component.

15. A method for preparing a binder composition characterized in that it comprises: mixing a silicate and a phosphate in the presence of water; wherein the mixing is carried out at room temperature in the absence of an aggregate.

16. A method for liquefying a gelled binder composition containing a mixture of aqueous silicate and phosphate components, characterized in that it comprises agitation of the gelled composition.

17. A method for liquefying a gelled binder composition containing a mixture of aqueous silicate and phosphate components, characterized in that it comprises the addition of water thereto.

18. A method for liquefying a gelled binder composition containing a mixture of aqueous silicate and phosphate components, characterized in that it comprises raising the pH of the mixture.

The method of claim 18, characterized in that the pH is raised by adding thereto at least one compound selected from the group consisting of alkali hydroxide and ammonium hydroxide.

20. A method for agglutinating particulate materials with a binder, the method is characterized in that it comprises: providing an aqueous binder system comprising a mixture of at least one silicate, at least one phosphate and the particulate materials that will be agglutinated; form the mixture, - and dehydrate the mixture.

The method of claim 20, characterized in that the step of dehydration dehydrates the mixture to a water content of less than 1% by weight, based on the weight of the particulate materials.

22. The method of claim 20, characterized in that the delivery of the at least one phosphate comprises the in situ formation of the phosphate.

23. The method of claim 22, characterized in that the formation in si tu comprises contacting a phosphoric acid with a base.

The method of claim 23, characterized in that the "in formation" comprises contacting a precursor phosphate with a member of the group consisting of an acid and a base to form the phosphate in situ.

25. A method for preparing conformations from particulate material, characterized in that it comprises: forming a mixture of the particulate material, a silicate, a phosphate and water; form a conformation with the mixture; and dehydrate the conformation.

26. The method of claim 25, characterized in that the step of dehydration comprises heating the shaping.

27. The method of claim 25, characterized in that the step of dehydration comprises forming in a heated box.

The method of claim 25, characterized in that the step of dehydration comprises blowing an inert gas through the shaping.

29. The method of claim 27, characterized in that the step of dehydration comprises blowing an inert gas through the shaping.

30. The method of claim 25, characterized in that the step of dehydration comprises the application of vacuum through the shaping.

The method of claim 27, characterized in that the step of dehydration comprises the application of vacuum through the shaping.

32. A method for preparing conformations from particulate material characterized in that it comprises: adding a binder comprising a silicate component and a phosphate component to a particulate material; mix the binder and the particulate material to form a mixture, - load the mixture in a heated pattern, - and cure the mixture.

33. The method of claim 32, characterized in that curing comprises dehydrating the mixture.

34. The method of claim 33, characterized in that the step of dehydration comprises blowing inert gas through the mixture.

35. The method of claim 34, characterized in that the inert gas is heated to at least about 90 ° C.

36. The method of claim 33, characterized in that the step of dehydration comprises applying vacuum through the mixture.

37. The method of claim 32, characterized in that the heated pattern is maintained at a temperature of at least about 90 ° C.

38. The method of claim 32, characterized in that the silicate and the phosphate are simultaneously added to the particulate material.

39. A mold removable in water characterized in that it comprises, a mass of shaped particles, the individual particles of the mass are bonded with a binder comprising at least one water-soluble silicate and at least one water-soluble phosphate, the resulting binder is soluble in water and has a water content less than 1% by weight based on the weight of the mold.

40. The mold of claim 39 is removable in water even when exposed to a temperature of up to 1200 ° C.

41. The mold of claim 39 is removable in water even when it is exposed to a temperature in the range of 700 ° -1200 ° C.

42. The mold of claim 39, characterized in that the particles are made of at least one material selected from the group consisting of silica, alumina, silicon carbide, magnesite, dolomite, aluminum silicate, mulite, carbon, forsterite, chromite. -magnesite, zircon, clay, chromite, chamotte and olivine.

43. A mold removable in water characterized in that it comprises, a mass of shaped particles, the individual particles of the mass are bonded with a binder comprising at least one water-soluble silicate and at least one water-soluble phosphate, wherein the mold It is a mold cured by heat.

44. The mold according to claim 43, characterized in that the particles are made of at least one material selected from the group consisting of silica, alumina, silicon carbide, magnesite, dolomite, aluminum silicate, carbon mullite, forsterite, chromite, magnesite, zircon, clay, chromite, chamotte and olivine.

45. A mold characterized in that it comprises a mass of agglutinated refractory particles, the mass is agglutinated with a binder comprising a silicate and a phosphate, the carbonate content of the mold is less than 0.05% by weight based on the weight of the mold.

46. The mold of claim 45, characterized in that the silicate and the phosphate are soluble in water, whereby the mold is removable in water.

47. The mold of claim 45, characterized in that the binder provides the mold with dry shake properties.

48. A method for increasing hot and cold tensile strengths of casting hearts and molds characterized in that it comprises: providing a binder containing sodium silicate and a phosphate in an aqueous medium; mix the binder with a casting sand; and then heal the binder with heat.

49. The method of claim 48, characterized in that the phosphate has "n" number of phosphate units (P? 3) nO) where n is an average number from 3 to 32 inclusive.

50. The method of claim 49, characterized in that n is 4 to 21 inclusive.

51. The method of claim 48, characterized in that the silicate has a SiO2: Na20 ratio of 0.6: 1 to 3.85: 1.

52. The method of claim 48, characterized in that the silicate: phosphate ratio ranges from 97.5: 2.5 to 5:95.

53. The method of claim 48, characterized in that no isomorphic replacement of the silicate ions with the phosphate ions occurs prior to mixing the aren with the binder.

54. The method of claim 20, characterized in that the aqueous binder system is formed by adding a solution of sodium silicate to an aqueous mixture of the particulate materials and the at least one phosphate.

55. A method for increasing the curing speed of a silicate binder characterized in that it comprises the addition of a soluble phosphate to the silicate binder.

56. A method for preparing a metallic melt characterized in that it comprises providing a mold according to claim 43 and casting a molten metal against the mold.

57. A method for preparing a metallic melt characterized in that it comprises providing a mold according to claim 45 and casting a molten metal against the mold.

58. A method for agglutinating particulate materials with a binder, the method is characterized in that it comprises: providing an aqueous binder system comprising a mixture of the at least one silicate, the at least one phosphate, X and the particulate materials which will be agglutinated; wherein the supply of the at least one phosphate comprises the in formation of the phosphate.