RU2844835C1 - Composition, core and mould for casting and moulding processes - Google Patents

Abstract

FIELD: foundry.

SUBSTANCE: proposed composition comprises refractory material in the form of particles, binder composition and, at least, one pozzolanic additive. Binder composition contains at least one hydrophilic polymer, wherein the at least one hydrophilic polymer comprises at least one polysaccharide or a polysaccharide derivative. Said binder, which is water-soluble, is added to the composition for making cores to wash the core out of the article with water. Introduction of the pozzolanic additive increases the strength of the core by increasing fluidity of the composition and improving its sealing.

EFFECT: providing sufficient strength of core for its use in casting or moulding processes with simultaneous ability of core to washout from inner cavity of cast or moulded article using only water.

33 cl, 2 dwg, 8 tbl, 4 ex

Description

Field of technology

The present invention relates to a composition for use as a core in a casting or molding process, to a core containing the composition, to casting molds containing the core, and to a method for manufacturing an article using the core. In particular, the present invention relates to a core that can be washed out of the interior of a cast or molded article using water.

State of the art

In a typical casting process, molten metal (or metal alloy) is poured into a pre-formed mold cavity that defines the shape of the casting, with the molten metal filling the mold cavity under gravity. The shape of the hollow sections or internal cavities of the casting may be defined by a disposable core, which is typically made of cured resin-bonded sand. During casting, the extreme heat from the molten metal thermally decomposes the resin binder in the core, allowing the core to break up and easily shake out of the finished casting as the molten metal cools and solidifies. However, in die casting processes in which the metal cools very quickly or the walls of the casting are relatively thin, the core may not be exposed to sufficient heat during the casting process to decompose the binder, making it very difficult to remove the core after the casting has solidified. Examples of such injection molding processes include high-pressure die casting, low-pressure die casting, high-vacuum die casting, semi-solid injection molding (e.g., rheocasting and thixocasting), permanent or semi-permanent mold casting, and extrusion molding. In such processes, the core can typically only be exposed to temperatures up to 300°C and for a limited time, which is not sufficient to thermally decompose traditional resin binders.

In high pressure die casting (HPDC), molten metal is injected into a mould cavity at high pressure (typically around 10-175 MPa) and held in place by compressive force until the metal solidifies. HPDC is extremely fast compared to gravity flow pouring, as the injection pressure causes the molten metal to fill the mould cavity in seconds (or even milliseconds), and the casting can be actively cooled, for example by internal water pipes in the mould wall. HPDC is particularly useful for casting thin-walled parts, where high pressure forces the liquid metal into tight spaces that gravity pouring cannot reach. The technology can therefore be used to reduce the weight of metal parts by allowing parts with thinner walls and hollow interiors to be cast.

Semi-solid injection molding involves a similar process in which the metal (or metal alloy) is injected into the mold (die) in a semi-solid state rather than a fully molten state. In this semi-solid state, the metal develops a globular microstructure that improves the kinematic viscosity and flowability of the metal and thereby improves the quality of the final casting. In rheocasting, the metal is cooled from a fully molten state to a semi-solid state prior to injection, whereas in thixocasting, the solid metal is partially melted to a semi-solid state. Semi-solid injection molding is typically used for high-production applications that require high-quality finishes.

Molds for traditional gravity casting processes are typically made of sand and may be disposable. On the other hand, injection molds are typically made of metal (such as steel) and may need to withstand high pressures and metal velocities. Injection molds may also include injection systems, water cooling systems, and/or vacuum systems. Due to the increased complexity of injection mold systems compared to traditional sand mold systems, the injection mold is often a permanent or semi-permanent mold, with disposable cores used to create the internal spaces in the casting.

In addition to being difficult or impossible to remove after use, traditional sand cores may not have sufficient strength to withstand the pressures and metal velocities involved in some die casting processes, such as HPDC or semi-solid die casting, and may fracture during such use. Traditional resin-bonded sand cores are therefore unsuitable for use in such die casting processes.

In an attempt to reduce these problems, some cores for use in die casting are made from salt, which can then be removed from the finished casting by dissolving in hot water. However, the salt can be molded into the desired core shape while in the molten mold, usually under high pressure, so making salt cores is difficult and expensive.

Other low temperature processes for making molded parts, such as carbon composite molding, can also exhibit the same core release issues. Carbon composite parts are typically autoclave cured at temperatures as high as 200°C, which is not hot enough to decompose the binder in a typical resin-bonded sand core, making it very difficult to remove the core from the interior cavity once the carbon composite part has been installed.

EP 2564951 A1 describes a molding or core sand that is bonded by a biodegradable polymer binder. However, the molding/core sand disclosed in this document is formulated for use in high temperature casting applications and requires the binder to undergo high temperature or microwave induced crosslinking for curing. The binder therefore relies on thermal degradation of the binder to allow the core to shake out of the finished casting and on crosslinking of the polymer for strength. As such, the cores disclosed in EP 2564951 A1 do not have the required strength for applications in which the core may not be exposed to high enough temperatures to crosslink the polymer binder during use, such as injection molding.

WO 2020/146452 A1 describes a method for producing a washout tool for molding carbon composites, which requires three-dimensional printing of a mixture of powdered quartz sand and an amine-containing adhesive polymer. The binder is only water-soluble up to 180°C and is therefore only suitable for ultra-low temperature applications such as molding carbon composites, but not for other applications such as injection molding, in which the core may be exposed to temperatures of up to 300°C.

The present invention is directed to overcoming the above-mentioned problems associated with removing an inner core from a cast or molded article, or at least to providing a useful alternative.

The essence of the invention

Composition

According to a first aspect of the invention, a composition for producing a core for use in a molding or casting process is provided. The composition comprises a refractory material in the form of particles, a binder composition containing at least one hydrophilic polymer, wherein the at least one hydrophilic polymer contains at least one polysaccharide or polysaccharide derivative, and at least one pozzolanic additive.

The inventors have found that rods made from the composition of the first aspect have sufficient strength to withstand the forces to which they are subjected during casting or molding processes, while being able to be washed out of the interior of a cast or molded article using only water. It should be understood that only some components of the composition need be soluble in water per se, while other components (such as the particulate refractory material) need not be soluble in water. However, a rod made from the composition of the first aspect may disintegrate in water due to the degradation of the components that bind the particulate refractory material (and any other insoluble components) together as the binding components dissolve or hydrate, and as such the rod may be referred to as "water soluble" for the purposes of this disclosure. Accordingly, the terms "water-soluble" and "water solubility" are used herein to describe the ability of a rod containing the composition of the first aspect to disintegrate in water, rather than the ability of the composition to form a solution in water.

In some embodiments, a rod made using the composition is water-soluble even after heating to at least 200°C. In some embodiments, a rod made using the composition is water-soluble after heating to a temperature of 200 to 350°C.

In some embodiments, the composition serves to produce a rod for use in an injection molding process and/or in a carbon composite molding process.

The composition of the first aspect is typically a granular solid, which may be substantially dry or partially wet depending on the liquid content and the relative proportion of the binder composition compared to the particulate refractory material used in the composition. Preferably, the composition is a flowable granular solid. In use, the composition is formed into a core in the outer mold of the inner cavity of the article to be cast or molded. The core is typically formed into the desired shape by compacting the core composition in a mold and then curing the composition, for example by drying. This may be achieved using sand-casting equipment. Alternatively, the core may be manufactured by an additive manufacturing process (3D printing). Without being limited by theory, it is believed that the binder composition may bind the particulate refractory material in the rod through physical interaction with the particulate refractory material (e.g., through interlocking or by holding the particulate refractory material in a matrix) as well as through or in place of chemical bonding.

According to the second aspect of the invention, a rod is provided, comprising the composition of the first aspect. The rod can be used in the process of molding or casting metals in order to define an internal cavity of a molded or cast article. In some embodiments, the rod is for use with a casting mold, such as an injection mold. In some embodiments, the rod is for use in the manufacture of a carbon composite article.

In some embodiments, the core comprises a surface coating. The surface coating may perform a number of different functions. For example, the surface may provide: a protective layer to prevent harmful interaction between the molten metal and the core composition; a sealant to prevent metal from entering between the grains of the particulate refractory material in the core, particularly at higher pressures; a smoothing effect on the surface of the core, which in turn may improve the finished surface of the casting; or non-stick properties to allow the core to be easily separated from the casting after solidification. The surface coating may be selected based on the material to be cast or molded, such as being non-wetting for the material to be cast or molded, and based on the function(s) to be provided by the coating. Any surface coating that is suitable for refractory applications may be used, such as coatings containing boron nitride, silicates, titanium dioxide, zirconium dioxide, or aluminum oxide. Surface coatings for refractory applications typically contain a binder that adheres the coating to the surface. In some embodiments of the present invention, the binder of the surface coating is water-soluble so that the coating can be washed out with the rest of the rod, instead of adhering to the surface of the article.

According to a third aspect of the invention, a casting mold is provided, comprising a core of the second aspect. In some embodiments, the casting mold serves to produce an article by casting, and the core serves to define an internal cavity of the article. In some embodiments, the casting mold serves for injection molding. In some embodiments, the casting mold is made of a metal, such as steel. In some embodiments, the casting mold serves for high-pressure casting or semi-solid injection molding.

Composition of the binder

It should be understood that the term "binder composition" as used herein means a composition containing compounds that bind the particulate refractory material. Preferably, the binder composition is an organic binder composition containing organic binder compounds. The binder composition may further contain non-binder components such as surfactants. The binder composition may also contain at least one solvent.

The binder composition comprises at least one hydrophilic polymer. In some embodiments, the binder composition further comprises at least one surfactant.

In some embodiments, when mixing the binder composition with the particulate refractory material to obtain the composition of the first aspect, the binder composition is provided as a pre-mix. In alternative embodiments, when mixing the binder composition with the particulate refractory material to obtain the composition of the first aspect, the binder composition is provided in the form of separate components that are combined together to provide the binder composition when mixed with the particulate refractory material. It should be understood that the resulting composition must contain all components of the binder composition, regardless of whether they are mixed with the particulate refractory material together or separately.

In some embodiments, the composition comprises at least 0.5, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, or at least 20% by weight of the composition of a binder based on the weight of the particulate refractory material. In some embodiments, the composition comprises no more than 50, no more than 40, no more than 30, no more than 20, no more than 15, no more than 10, no more than 5, no more than 2, or no more than 1 wt. % of the binder composition based on the weight of the particulate refractory material. In some embodiments, the binder composition comprises 0.5 to 30, 1 to 20, 2 to 15, or 2 to 10 wt. % of the binder composition based on the weight of the particulate refractory material.

The inventors have found that the viscosity of the binder composition can affect the flowability of the composition, which in turn can affect the ease of manufacture and performance of a core made from the composition. Without being limited by theory, it is believed that a higher flowability of the composition allows the composition to be more easily released from the core-throwing equipment, thereby preventing blockages in the equipment, and to flow into all parts of the core mold cavity so that even a complex core mold cavity can be completely filled without any gaps or voids, thereby increasing the strength of the core and reducing waste due to defective cores. In addition, it is believed that a higher flowability allows for better tight packing and compaction of the composition, which can also contribute to increased core strength.

In general, it has been found that a lower viscosity of the binder composition results in a higher flowability of the composition, and vice versa. A lower viscosity can also help to ensure uniform distribution of the binder composition when mixed with the particulate refractory, which in turn can improve the bonding between the particles, thereby increasing the strength of the core. However, it should be understood that the overall viscosity/flowability of the composition must be balanced with other factors that affect the strength of the resulting core, since a binder composition that is highly diluted to achieve a low viscosity may provide a highly flowable composition, but may not achieve adequate bonding of the particulate refractory, which has a negative effect on the strength of the core.

In some embodiments, the binder composition has a dynamic viscosity at 23°C of no more than 1 Pa*s, no more than 500 mPa*s, no more than 400 mPa*s, no more than 300 mPa*s, or no more than 200 mPa*s. In some embodiments, the binder composition has a dynamic viscosity at 23°C of at least 5 mPa*s, at least 10 mPa*s, at least 20 mPa*s, at least 50 mPa*s, at least 100 mPa*s, or at least 200 mPa*s. In some embodiments, the binder composition has a dynamic viscosity at 23°C of 5 mPas to 1 Pas, 10 mPas to 500 mPas, or 20 mPas to 400 mPas.

It should be understood that the viscosity of the binder composition is the viscosity measured before the binder composition is mixed with the particulate refractory material to formulate the composition, i.e., the viscosity of the binder composition in isolation. It should also be understood that in embodiments in which the pozzolanic additive, when present, is mixed with the binder composition before the binder composition is mixed with the particulate refractory material to formulate the composition, the viscosity of the binder composition is the viscosity of the binder composition alone, and not the viscosity of the binder composition/pozzolanic additive mixture. It should also be understood that in embodiments in which the binder composition is mixed with the particulate refractory material in the form of individual components rather than as a premix, the viscosity of the binder composition is considered to be the total viscosity that the binder composition would have if the individual components of the binder composition were mixed together to provide a premix prior to production.

It should be understood that the viscosity of the binder composition as a whole can be affected by the viscosity of the individual components included therein, for example, the viscosity of at least one hydrophilic polymer, as well as the dilution level of the binder composition. The viscosity of the binder composition can also potentially be affected by viscosity-modifying interactions between the individual components.

In some embodiments, the binder composition comprises at least one solvent, such as water. The solvent may be used to dissolve or hydrate the binder composition components that are supplied in solid form, to ensure proper dispersion of the binder components in the particulate refractory material and/or to dilute the binder composition in order to achieve the desired viscosity. It should be understood that in some embodiments, the binder composition components are supplied in solution, such as an aqueous solution, and therefore at least a portion of the solvent in the binder composition is provided by the component(s) that are supplied in solution. In some such embodiments, additional solvent does not necessarily need to be added to the binder composition in order to achieve proper dispersion and/or the desired viscosity. However, in some embodiments, additional solvent must be added to the binder composition to supplement the amount of solvent provided by the component(s) supplied in solution and to increase the total amount of solvent in the binder composition.

In some embodiments, the binder composition comprises at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, or at least 70 wt. % solvent based on the total weight of the binder composition. In some embodiments, the binder composition comprises no more than 80, no more than 70, no more than 60, no more than 50, no more than 40, no more than 30, or no more than 20 wt. % solvent based on the total weight of the binder composition. In some embodiments, the binder composition comprises 10 to 80, 20 to 70, 30 to 70, or 40 to 70 wt. % solvent based on the total weight of the binder composition.

Hydrophilic polymers

Hydrophilic polymers can generally be considered polymers that have preferential interactions with water molecules, as opposed to hydrophobic polymers, which repel water. Hydrophilic polymers may be water-soluble or may absorb/adsorb water, such as to cause swelling or gel formation. Hydrophilic polymers typically contain charged or polar functional groups that attract water molecules.

In the present invention, the binder composition comprises at least one hydrophilic polymer. The at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative. In some embodiments, the at least one hydrophilic polymer may further comprise at least one synthetic polymer, at least one additional polysaccharide or polysaccharide derivative, or mixtures thereof.

In some embodiments, at least one hydrophilic polymer is in solution, such as in an aqueous solution. In some embodiments in which the binder composition comprises more than one hydrophilic polymer, at least one of the hydrophilic polymers may be in solution. In some embodiments in which the binder composition comprises more than one hydrophilic polymer, all of the hydrophilic polymers may be in solution.

In some embodiments, the hydrophilic polymer solution has a solids content of no more than 80%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, or no more than 30% w/v. In some embodiments, the hydrophilic polymer solution has a solids content of at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% w/v. In some embodiments, the hydrophilic polymer solution has a solids content of 10% to 80%, or 10% to 50% w/v. It should be understood that the solids content of the solution can be selected to achieve the desired viscosity of the binder composition, as mentioned above.

In some embodiments, the binder composition comprises at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, or at least 70 wt. % of a hydrophilic polymer based on the total weight of the binder composition. In some embodiments, the binder composition comprises no more than 80, no more than 70, no more than 60, no more than 50, no more than 40, no more than 30, or no more than 20 wt. % of a hydrophilic polymer based on the total weight of the binder composition. In some embodiments, the binder composition comprises 10 to 80, 20 to 70, 20 to 60, or 30 to 60 wt. % of a hydrophilic polymer based on the total weight of the binder composition.

In some embodiments, the hydrophilic polymer can comprise at least 0.5, at least 0.75, at least 1, at least 1.25, at least 1.5, at least 2, at least 2.5, at least 3, at least 4, or at least 5 wt.% of the composition based on the weight of the refractory material.

In some embodiments, wherein the at least one hydrophilic polymer is in solution, the binder composition comprises at least 50, at least 60, at least 70, at least 80, at least 90, at least 95, at least 99, or at least 99.5 wt. % of a hydrophilic polymer solution based on the total weight of the binder composition. In some embodiments, the binder composition comprises no more than 99.5, no more than 99, no more than 95, no more than 90, no more than 80, no more than 70, or no more than 60 wt. % of a hydrophilic polymer solution based on the total weight of the binder composition. In some embodiments, the binder composition comprises from 50 to 100, from 70 to 100, or from 80 to 99.5 wt. % of a hydrophilic polymer solution based on the total weight of the binder composition.

In some embodiments, the at least one hydrophilic polymer does not undergo crosslinking when the composition is heated at temperatures of up to 250°C, up to 300°C, or up to 350°C. In some embodiments, the at least one hydrophilic polymer does not undergo crosslinking when the composition is heated to a temperature of from 200 to 350°C.

Without being limited by theory, it is believed that temperature-induced crosslinking of at least one hydrophilic polymer can reduce the water solubility of the rod by changing the structural properties of the polymer such that dissolution or hydration of the polymer in water is prevented. Accordingly, hydrophilic polymers that do not undergo crosslinking when the composition is heated at temperatures up to 350 °C allow the production of rods that have good water solubility even after exposure to elevated temperatures during the casting or molding process. However, hydrophilic polymers that undergo crosslinking at lower temperatures (e.g., between 200 and 300 °C) may still be suitable for lower temperature applications down to 200 °C, such as molding carbon composites or casting metals or alloys with relatively low melting points. Furthermore, in practice, only the outer edges or very thin sections of the rod are likely to reach temperatures of up to 300°C (or more) during use. It should therefore be understood that suitable hydrophilic polymers may be selected based on the casting or molding process for which the composition is used and on the shape and dimensions of the intended rod.

Synthetic polymers

Synthetic polymers are generally considered to be polymers that are man-made rather than naturally occurring. Synthetic polymers can be homopolymers, containing only one type of monomer, or copolymers, containing two or more different types of monomer.

In some embodiments, the at least one hydrophilic polymer comprises at least one synthetic polymer. In some embodiments, the at least one synthetic polymer is selected from the group consisting of polyacrylates, acrylate copolymers, polyvinyl alcohol, polyphosphates, polymetaphosphates, and mixtures thereof. In embodiments in which the binder composition is an organic binder composition, the at least one synthetic polymer is selected from the group consisting of polyacrylates, acrylate copolymers, polyvinyl alcohol, and mixtures thereof.

The inventors have found that polyacrylates and polyphosphates in particular provide rods that have excellent strength and water solubility. Furthermore, the inventors have found that polyacrylates and polyphosphates are unlikely to crosslink at temperatures up to 300°C and provide rods with excellent water solubility even after prolonged exposure to such temperatures, whereas polyvinyl alcohol, for example, can crosslink at temperatures above 200°C and may therefore be suitable for lower temperature applications.

In some embodiments, at least one synthetic polymer comprises an alkali salt of a polyacrylate, an acrylate copolymer, or a polyphosphate. In some embodiments, the alkali salt is a sodium salt or a potassium salt. It has been found that alkali salts, such as sodium polyacrylate or sodium polyphosphate, allow the production of rods with very good water solubility, while it has been found that ammonium salts, such as ammonium polyacrylate, allow the production of rods that are less water soluble.

In some embodiments, the at least one synthetic polymer comprises a polyphosphate having a chain length of at least 4, at least 5, at least 6, at least 7, at least 10, at least 12, at least 15, at least 20, at least 25, or at least 30. In some embodiments, the at least one synthetic polymer comprises an alkaline polyphosphate having a chain length of 4 to 30.

At least one synthetic polymer is preferably environmentally friendly, which facilitates the safe disposal or reuse of water used to rinse the rod after use. In some embodiments, at least one synthetic polymer comprises an alkaline polyacrylate salt that is non-hazardous.

In some embodiments, the at least one synthetic polymer has a molecular weight of at most 1,000,000 g/mol, at most 500,000 g/mol, at most 100,000 g/mol, at most 50,000 g/mol, at most 10,000 g/mol, or at most 5,000 g/mol. In some embodiments, the at least one synthetic polymer is in solution, such as in an aqueous solution. In some embodiments, the synthetic polymer solution has a solids content of at most 80%, at most 70%, at most 60%, at most 50%, at most 40%, or at most 30% w/v. In some embodiments, the synthetic polymer solution has a solids content of at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% w/v. In some embodiments, the synthetic polymer solution has a solids content of 10% to 80%, or 10% to 50% w/v.

In some embodiments, the at least one synthetic polymer or (if in solution) the solution of the synthetic polymer has a dynamic viscosity at 23°C of no more than 1 Pa*s, no more than 500 mPa*s, no more than 400 mPa*s, no more than 300 mPa*s, or no more than 200 mPa*s. In some embodiments, the at least one synthetic polymer or the solution of the synthetic polymer has a dynamic viscosity at 23°C of at least 5 mPa*s, at least 10 mPa*s, at least 20 mPa*s, at least 50 mPa*s, at least 100 mPa*s, or at least 200 mPa*s. In some embodiments, the at least one synthetic polymer or synthetic polymer solution has a dynamic viscosity at 23°C of from 5 mPa*s to 1 Pa*s, from 10 mPa*s to 500 mPa*s, or from 20 mPa*s to 400 mPa*s. It should be understood that the molecular weight of the at least one synthetic polymer and/or the solids content of the solution (if the at least one synthetic polymer is in solution) can be selected to achieve the desired viscosity. It should also be understood that the viscosity of the at least one synthetic polymer or synthetic polymer solution is a viscosity measured before the at least one synthetic polymer or synthetic polymer solution is mixed with the binder composition and/or the particulate refractory material to formulate the composition, i.e. viscosity of at least one synthetic polymer or synthetic polymer solution in isolation.

In some embodiments, the at least one hydrophilic polymer comprises at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, or at least 90 wt. % of a synthetic polymer based on the total weight of the hydrophilic polymer. In some embodiments, the at least one hydrophilic polymer comprises no more than 100, no more than 90, no more than 80, no more than 70, no more than 60, no more than 50, no more than 40, no more than 30, or no more than 20 wt. % of a synthetic polymer based on the total weight of the hydrophilic polymer. In some embodiments, the at least one hydrophilic polymer comprises from 10 to 100, from 20 to 90, from 30 to 80, or from 50 to 80% by weight of a synthetic polymer based on the total weight of the hydrophilic polymer.

In some embodiments, the synthetic polymer may comprise at least 0.5, at least 0.75, at least 1, at least 1.25, at least 1.5, at least 2, at least 2.5, at least 3, at least 4, or at least 5 wt.% of the composition based on the weight of the refractory material.

Polysaccharides and polysaccharide derivatives

Polysaccharides are carbohydrates that contain a chain of monosaccharide units. Examples of polysaccharides include starch, glycogen, cellulose, and pectin, among others. Polysaccharide derivatives can generally be considered compounds that are formed from a polysaccharide through a chemical reaction, such as hydrolysis or the addition of a functional group. Polysaccharide derivatives can also be known as modified polysaccharides, such as modified starch.

In the present invention, the at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative (abbreviated hereinafter as "at least one polysaccharide"). In some embodiments, the at least one polysaccharide is selected from the group consisting of starch, starch derivatives, cellulose, cellulose derivatives, and mixtures thereof. Polysaccharides or polysaccharide derivatives suitable for use with the present invention include dextrin, potato starch, carboxymethylcellulose, and mixtures thereof.

In some embodiments, the at least one polysaccharide is in a solution, such as an aqueous solution. In some embodiments, the polysaccharide solution has a solids content of no more than 80%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, or no more than 30% w/v. In some embodiments, the polysaccharide solution has a solids content of at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% w/v. In some embodiments, the polysaccharide solution has a solids content of 10% to 80%, or 10% to 50% w/v.

In some embodiments, the at least one polysaccharide or (if in solution) the polysaccharide solution has a dynamic viscosity at 23°C of no more than 1 Pa*s, no more than 500 mPa*s, no more than 400 mPa*s, no more than 300 mPa*s, or no more than 200 mPa*s. In some embodiments, the at least one polysaccharide or polysaccharide solution has a dynamic viscosity at 23°C of at least 5 mPa*s, at least 10 mPa*s, at least 20 mPa*s, at least 50 mPa*s, at least 100 mPa*s, or at least 200 mPa*s. In some embodiments, the at least one polysaccharide or polysaccharide solution has a dynamic viscosity at 23°C of from 5 mPa*s to 1 Pa*s, from 10 mPa*s to 500 mPa*s, or from 20 mPa*s to 400 mPa*s. It should be understood that the solids content of the polysaccharide solution can be selected so as to achieve the desired viscosity. It should also be understood that the viscosity of the at least one polysaccharide or polysaccharide solution is a viscosity measured before the at least one polysaccharide or polysaccharide solution is mixed with the binder composition and/or the particulate refractory material to formulate the composition, i.e., the viscosity of the at least one polysaccharide or polysaccharide solution in isolation.

In some embodiments, the at least one hydrophilic polymer comprises at least 5, at least 10, at least 20, at least 30, at least 50, at least 60, at least 70, at least 80, or at least 90 wt. % polysaccharide based on the total weight of the hydrophilic polymer. In some embodiments, the binder composition comprises no more than 100, no more than 90, no more than 80, no more than 70, no more than 60, no more than 50, no more than 30, no more than 20, or no more than 10 wt. % polysaccharide based on the total weight of the hydrophilic polymer. In some embodiments, the binder composition comprises 5 to 100, 5 to 90, 10 to 70, or 20 to 70 wt. polysaccharide based on the total mass of the hydrophilic polymer.

In some embodiments, the at least one hydrophilic polymer comprises polyacrylate as a synthetic polymer and dextrin as a polysaccharide derivative. In other embodiments, the at least one hydrophilic polymer comprises polyphosphate as a synthetic polymer and one or more of potato starch and carboxymethylcellulose as a polysaccharide and polysaccharide derivatives. In other embodiments, the at least one hydrophilic polymer comprises polyvinyl alcohol as a synthetic polymer and potato starch as a polysaccharide.

In some embodiments, the at least one hydrophilic polymer comprises from 30 to 80 wt. % of a synthetic polymer and from 20 to 70 wt. % of a polysaccharide based on the total weight of the hydrophilic polymer. In some embodiments, the at least one hydrophilic polymer comprises from 50 to 80 wt. % of a polyacrylate and from 20 to 50 wt. % of a dextrin based on the total weight of the hydrophilic polymer, wherein the polyacrylate can be an alkaline polyacrylate salt. In some embodiments, the at least one hydrophilic polymer comprises from 30 to 70 wt. % of a polyphosphate, from 15 to 40 wt. % of a carboxymethyl cellulose, and from 15 to 40 wt. % of a potato starch based on the total weight of the hydrophilic polymer, wherein the polyphosphate can be an alkaline polyphosphate salt.

In some embodiments, the polysaccharide or polysaccharide derivative may comprise at least 0.5, at least 0.75, at least 1, at least 1.25, at least 1.5, at least 2, at least 2.5, at least 3, at least 4, or at least 5% by weight of the composition based on the weight of the refractory material.

Plasticizers

In some embodiments, the binder composition comprises at least one plasticizer. In some embodiments, the at least one plasticizer comprises one or more polyols or polyol derivatives. Polyols suitable for use as plasticizers in the present invention include glycerol, sorbitol, xylitol, malitol, and mixtures thereof. Polyol derivatives suitable for use as plasticizers in the present invention include triglycerides, such as triacetin.

Providing at least one plasticizer in the binder composition can improve the tension at break values of the rod by lowering the glass transition temperature of the at least one hydrophilic polymer.

In some embodiments, at least one plasticizer is in solution, such as an aqueous solution. In some embodiments in which the binder composition comprises more than one plasticizer, at least one of the plasticizers may be in solution, such as an aqueous solution. In some embodiments in which the binder composition comprises more than one plasticizer, all of the plasticizers may be in solution, such as an aqueous solution. In some embodiments, the plasticizer solution has a solids content of no more than 50%, no more than 40%, or no more than 30% w/v. In some embodiments, the plasticizer solution has a solids content of at least 10%, at least 20%, at least 30%, or at least 40% w/v.

In some embodiments, the binder composition comprises at least 0.01, at least 0.05, at least 0.1, at least 0.2, at least 0.5, or at least 1 wt. % of a plasticizer or plasticizer solution based on the weight of the binder composition. In some embodiments, the binder composition comprises no more than 2, no more than 1, no more than 0.5, no more than 0.2, no more than 0.1, or no more than 0.05 wt. % of a plasticizer or plasticizer solution based on the weight of the binder composition. In some embodiments, the binder composition comprises 0.01 to 2, 0.05 to 1, or 0.1 to 1 wt. % of a plasticizer or plasticizer solution based on the weight of the binder composition.

In some embodiments, the binder composition comprises at least one plasticizer, and the at least one hydrophilic polymer comprises at least one synthetic polymer. In some embodiments, the binder composition comprises at least one plasticizer, and the at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative. In some embodiments, the binder composition comprises at least one plasticizer, and the at least one hydrophilic polymer comprises at least one synthetic polymer and at least one polysaccharide or polysaccharide derivative.

Polyols or polyol derivatives may be particularly suitable for use as plasticizers in compositions comprising polyvinyl alcohol as a synthetic polymer. In some embodiments, the at least one hydrophilic polymer comprises polyvinyl alcohol as a synthetic polymer, and the binder composition comprises one or more of sorbitol and glycerol as plasticizers. In some such embodiments, the binder composition comprises 50 to 90 wt. % sorbitol and 10 to 50 wt. % glycerol, based on the total weight of the plasticizer. In some such embodiments, the at least one hydrophilic polymer further comprises potato starch as a polysaccharide.

Surfactants

In some embodiments, the composition comprises at least one surfactant. The at least one surfactant may be selected from the group consisting of anionic, cationic, nonionic and amphoteric surfactants and mixtures thereof. Types of surfactant suitable for use in the present invention include sulfates, methosulfates, linear alcohol sulfates, sulfonates, sulfosuccinates, phosphate esters, glucosides and mixtures thereof. In particular, at least one surfactant may be selected from the group consisting of 2-ethylhexyl sulfosuccinate, 2-ethylhexyl sulfate, dodecylbenzenesulfonate, nonylphenol sulfate, sodium laureth sulfate, 3-ethylhexyl phosphate ether, undecylamidopropyltrimethylammonium methosulfate, ammonium methosulfate based on alkyl polyglycol ether, 2-ethylhexyl glucoside, hexyl glucoside and mixtures thereof.

The inventors have found that a high surface tension binder composition can reduce the flowability of the composition, and that adding a small amount of surfactant can significantly increase the flowability of the composition by reducing the surface tension of the binder composition. In turn, the increased flowability of the composition leads to a rod having increased strength, for the reasons mentioned earlier.

In some embodiments, the composition comprises at least 0.01, at least 0.02, at least 0.05, at least 0.1, at least 0.2, at least 0.5, or at least 1 wt. % surfactant based on the weight of the binder composition. In some embodiments, the composition comprises no more than 2, no more than 1, no more than 0.5, no more than 0.2, no more than 0.1, no more than 0.05, or no more than 0.02 wt. % surfactant based on the weight of the binder composition. In some embodiments, the composition comprises 0.01 to 2, 0.05 to 1, or 0.1 to 1 wt. % surfactant based on the weight of the binder composition.

In some embodiments, the composition comprises from 0.1 to 1% by weight of a sulfosuccinate surfactant based on the weight of the binder composition, wherein the sulfosuccinate surfactant can be 2-ethylhexyl sulfosuccinate.

Pozzolanic additives

In the invention, the composition comprises at least one pozzolanic additive. The pozzolanic additive is typically a fine powder material. In some embodiments, the at least one pozzolanic additive comprises alumina, siliceous or aluminosilicate powder or mixtures thereof. The at least one pozzolanic additive may be selected from the group consisting of silica dust, fly ash, rice husk ash, diatomaceous earth, volcanic ash, metakaolin and mixtures thereof. In some embodiments, the at least one pozzolanic additive comprises spherical particles and/or cenospheres (wherein the cenospheres are lightweight, hollow spheres).

In some embodiments, the at least one pozzolanic additive has a D50 particle diameter of at most 20 μm, at most 10 μm, at most 5 μm, at most 2 μm, at most 1 μm, at most 0.5 μm, or at most 0.1 μm. In some embodiments, the at least one pozzolanic additive has a D50 particle diameter of at least 0.01 μm, at least 0.05 μm, at least 0.1 μm, or at least 0.5 μm. In some embodiments, the at least one pozzolanic additive has a D50 particle diameter of 0.01 μm to 50 μm, 0.01 to 20 μm, 0.01 to 10 μm, 0.01 μm to 5 μm, or 0.01 μm to 2 μm.

The inventors have found that the addition of a pozzolanic additive significantly increases the strength of the rod. The inventors have also found that spherical pozzolanic particles and/or cenospheres significantly improve the flowability and compaction of the composition and therefore the strength of the rod. In addition, it has been found that pozzolanic additives having a relatively small D50 diameter lead to very good strength performance.

In some embodiments, the composition comprises at least 0.5, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, or at least 30 wt. % pozzolanic additive based on the weight of the particulate refractory material. In some embodiments, the binder composition comprises no more than 20, no more than 10, no more than 5, no more than 2, or no more than 1 wt. pozzolanic additive based on the weight of the particulate refractory material. In some embodiments, the composition comprises 0.5 to 20, 1 to 10, or 2 to 10 wt. % pozzolanic additive based on the weight of the particulate refractory material.

In some embodiments, at least one pozzolanic additive comprises spherical particles of quartz dust having a particle diameter D50 of less than 2 μm. In some embodiments, the composition comprises from 1 to 10 wt. % of spherical particles of quartz dust based on the weight of the refractory material, wherein the spherical particles of quartz dust may have a particle diameter D50 of less than 2 μm.

In some embodiments, the composition comprises both at least one pozzolanic additive and at least one surfactant.

Refractory material in particle form

In some embodiments, the particulate refractory material comprises sand. The sand may be any type of sand suitable for use in refractory applications, such as quartz sand. In some embodiments, the particulate refractory material may comprise any one or more conventional refractory materials, such as oxides, carbides, nitrides, etc. of silicon, aluminum, magnesium, calcium, and zirconium and other elements. Suitable refractory materials include, but are not limited to, quartz, olivine, chromite, zircon, and aluminum oxide. In some embodiments, the particulate refractory material comprises spherical particles and/or cenospheres, such as fly ash. In some embodiments, the particulate refractory material comprises a mixture of sand and spherical particles and/or cenospheres, such as a mixture of sand and fly ash.

In embodiments in which the particulate refractory material and the pozzolanic additive comprise spherical particles and/or cenospheres, the particulate refractory material and the pozzolanic additive may comprise the same type of spherical particles and/or cenospheres, such as fly ash. Alternatively, the particulate refractory material and the pozzolanic additive may comprise different types of spherical particles and/or cenospheres, such as the particulate refractory material may comprise fly ash while the pozzolanic additive comprises quartz dust. It should be understood that in embodiments in which the particulate refractory material and the pozzolanic additive comprise the same type of spherical particles and/or cenospheres, the D50 particle size of the particulate refractory material must be greater than the D50 particle size of the pozzolanic additive, so that the particulate refractory material is different from the pozzolanic additive.

In some embodiments, the particulate refractory material has a D50 particle diameter of at least 20 μm, at least 50 μm, at least 100 μm, at least 250 μm, or at least 500 μm. In some embodiments, the particulate refractory material has a D50 particle diameter of no more than 2 mm, no more than 1 mm, or no more than 500 μm. In some embodiments, the particulate refractory material has a D50 particle diameter of 20 μm to 2 mm, 50 μm to 2 mm, or 50 μm to 1 mm.

Casting molds

According to the fourth aspect of the invention, a casting mold is provided for producing an article by high-pressure casting or semi-solid pressure casting. The casting mold comprises a core for defining an internal cavity of the article, and the core comprises a hardened core composition. The hardened core composition comprises a refractory material in the form of particles and a binder composition. The hardened core composition degrades in water in such a way that a cylinder of the hardened core composition, having a maximum height of 80 mm and a maximum diameter of 50 mm, disintegrates in no more than 10 minutes when immersed in water at a temperature of 20°C and stirred at a rotation speed of 60 rpm. The hardened core composition has a bending strength of at least 300 N/cm ² .

A high-pressure die casting or semi-solid die casting mold is typically made of steel or another metal with a high melting point and is typically formed in two parts (called "molds" or half-molds) that are tightly closed during use to create a sealed casting cavity. A high-pressure die casting or semi-solid die casting mold typically includes a system for injecting molten metal into the casting cavity. The mold may also include a water cooling system within the walls of the mold. High-pressure die casting may be considered a die casting process in which metal is injected and/or compressed at pressures ranging from approximately 10 MPa to approximately 175 MPa.

The inventors have found that a solidified core composition comprising a particulate refractory material and a binder composition that disintegrates in no more than 10 minutes when stirred with water and has a flexural strength of at least 300 N/ ^cm2 can be used to produce a core that has sufficient strength to withstand the forces of HPDC or semi-solid die casting and can also be easily removed from the casting by washing with water. The casting mold of the fourth aspect of the invention therefore provides a more convenient and less expensive means for producing castings with internal cavities by HPDC and semi-solid die casting.

In some embodiments, the solidified core composition disintegrates in no more than 5 minutes, no more than 2 minutes, no more than 1 minute, or no more than 30 seconds. Higher disintegration rates are preferred, if possible, in order to increase productivity during industrial production of castings. In some embodiments, the disintegration time may be reduced by increasing the water temperature and/or by increasing the agitation of the water. In practice, it should be understood that the level of agitation should be high since the solidified core composition should be washed out of the casting using a stream of water. The water used to wash the solidified core composition is typically room temperature in practice, but warm or hot water (for example, up to 70 ° C) may be used. The stated conditions of 20 ° C and 60 rpm are therefore intended to represent the least favorable conditions that should be encountered in practice, under which water solubility is expected to be minimal. It should be understood that if the set rod composition disintegrates in less than 10 minutes under these conditions, the set rod composition is expected to be at least as water soluble under improved conditions (i.e., higher temperature and agitation), if not more so.

In some embodiments, the cylinder of the hardened rod composition disintegrates in water even after heating to a temperature of at least 200°C. In some embodiments, the cylinder of the hardened rod composition disintegrates in water after heating to a temperature of 200 to 350°C.

In some embodiments, the hardened core composition has a flexural strength of at least 500 N/cm ² , at least 750 N/cm ³ , or at least 1000 N/cm ² . Higher flexural strengths are preferred, if possible, to reduce the likelihood of core cracking during casting.

In some embodiments, the binder composition comprises at least one hydrophilic polymer.

In some embodiments, the at least one hydrophilic polymer comprises at least one synthetic polymer. The at least one synthetic polymer may be selected from the group consisting of polyacrylates, acrylate copolymers, polyphosphates, polymetaphosphates, polyvinyl alcohol, and mixtures thereof. In some embodiments, the at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative. The at least one polysaccharide or polysaccharide derivative may be selected from the group consisting of starch, starch derivatives, cellulose, cellulose derivatives, and mixtures thereof.

In some embodiments, the at least one hydrophilic polymer does not undergo crosslinking when the composition is heated at temperatures of up to 250°C, up to 300°C, or up to 350°C. In some embodiments, the at least one hydrophilic polymer does not undergo crosslinking when the composition is heated to a temperature of from 200 to 350°C.

In some embodiments, the hardened rod composition comprises at least one pozzolanic additive. In some embodiments, the at least one pozzolanic additive comprises alumina, siliceous or aluminosilicate powder or mixtures thereof. The at least one pozzolanic additive may be selected from the group consisting of silica dust, fly ash, rice husk combustion ash, diatomaceous earth, volcanic ash, metakaolin and mixtures thereof. In some embodiments, the at least one pozzolanic additive comprises spherical particles and/or cenospheres.

In some embodiments, the particulate refractory material comprises quartz sand. In some embodiments, the particulate refractory material comprises spherical particles and/or cenospheres. In some embodiments, the particulate refractory material comprises fly ash. In some embodiments, the particulate refractory material has a particle diameter D50 of at least 50 μm.

The hardened rod composition may comprise the composition according to the first aspect. It should be understood that any of the embodiments explained with respect to the first aspect may be freely combined and applied to the hardened rod composition of the fourth aspect.

In some embodiments, a surface coating is applied to the rod. The surface coating may be any coating suitable for refractory applications, such as coatings containing boron nitride, silicates, titanium dioxide, zirconium dioxide, and/or aluminum oxide.

Methods

According to a fifth aspect of the invention, a method for producing an article by high-pressure casting or semi-solid injection molding is provided. The method comprises the following steps:

(i) mixing the composition as described herein to form a mixture;

(ii) moulding and hardening the mixture to form a core in the shape of the internal cavity of the article;

(iii) assembling the core with a high-pressure die casting or semi-solid die casting mold such that the mold and the core together define a casting cavity;

(iv) injecting molten or semi-solid metal into a casting cavity until the cavity is filled;

(v) cooling and causing the molten or semi-solid metal to solidify in order to form an article, the core being contained within the internal cavity of the article;

(vi) removing the article containing the core from the mould; and

(vii) removing the rod from the internal cavity by rinsing with water.

It should be understood that in the step of mixing the particulate refractory material and the binder composition to form the mixture, the binder composition may be provided as a pre-mix, a partially pre-mix, or as separate components that are combined together to provide the binder composition when mixed with the particulate refractory material. In some embodiments, the binder composition may be partially pre-mixed and subsequently mixed with additional components to form the binder composition. In some embodiments, the binder composition may be partially pre-mixed and thereby provided as a first mixture containing all liquid components. The first mixture may then be supplemented with one or more dry components to form the binder composition. The partially pre-mixed binder composition may comprise a polysaccharide or a polysaccharide derivative and, optionally, one or more of the following: an additional hydrophilic polymer, a synthetic polymer, and a surfactant. In some embodiments, the binder composition may be pre-mixed with the pozzolanic additive prior to mixing with the particulate refractory material.

In some embodiments, the binder composition comprises at least one hydrophilic polymer.

In some embodiments, the at least one hydrophilic polymer comprises at least one synthetic polymer. In some embodiments, the at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative. In some embodiments, the at least one hydrophilic polymer is in solution. In some embodiments, the binder composition comprises at least one surfactant. It should be understood that the synthetic polymers, polysaccharides and surfactants suitable for use with the fifth aspect, and their amounts and characteristics, are identical to what is described with respect to the first aspect.

In some embodiments, the at least one hydrophilic polymer is not crosslinked during any step of the method.

In some embodiments, the particulate refractory material comprises quartz sand. In some embodiments, the particulate refractory material comprises spherical particles and/or cenospheres. In some embodiments, the particulate refractory material comprises fly ash. In some embodiments, the particulate refractory material has a particle diameter D50 of at least 50 μm.

In some embodiments, the binder composition comprises at least one surfactant.

In some embodiments, the step of mixing the refractory particulate material and the binder composition to form a mixture includes mixing at least one pozzolanic additive with the refractory particulate material and the binder composition to form the mixture. It should be understood that the pozzolanic additives suitable for use with the fifth aspect and their amounts and characteristics are identical to what is described with respect to the first aspect.

In some embodiments, the mixture is a composition according to the first aspect. It should be understood that any of the embodiments explained with respect to the first aspect can be freely combined and applied to the mixture of the fifth aspect.

In some embodiments, the step of molding and curing the mixture includes compacting the mixture into a core mold. In some embodiments, the step of molding and curing the mixture includes drying the mixture. In some embodiments, the step of molding and curing the mixture is performed using sand-casting core equipment. In some embodiments, the step of molding and curing the mixture to produce a core includes producing the core by an additive manufacturing process or three-dimensional printing.

In some embodiments, the method further comprises the step of applying a surface coating to the rod before assembling the rod with the mold. The surface coating may be identical to the coating described in relation to the second and fourth aspects of the invention.

Brief description of the drawings

Fig. 1a is a schematic view of a high pressure casting mould according to an embodiment of the present invention in an open position;

Fig. 1b is a schematic view of the high pressure die casting mould shown in Fig. 1a in a closed position.

Detailed description of the invention

Fig. 1a shows an example of a high-pressure casting mould 100 according to an embodiment of the present invention in an open position. The casting mould 100 comprises a first mould half 2 mounted on a fixed plate 4 and a second mould half 3 mounted on a movable plate 6. A core 8 according to the present invention is mounted on the first mould half 2. In use, the movable plate 6 moves towards the fixed plate 4, bringing the mould halves 2, 3 together in a closed position (shown in Fig. 1b). The casting cavity 10 is defined between the mould halves 2, 3 and the core 8.

The casting mold 100 also comprises an injection system 12 for injecting molten metal 14 into the casting cavity 10. The injection system 12 comprises a chamber 16 for holding molten metal 14 and a piston 18 for pushing molten metal 14 through the chamber 16 and into the casting cavity 10 via a feeder 20 defined between the first and second mold halves 2, 3. The molten metal may be fed into the injection system by any suitable means, such as by immersion in a pool or crucible of molten metal. In the embodiment illustrated in Fig. 1a and 1b, molten metal 14 is fed into the injection system 12 by pouring molten metal 14 from a ladle or pouring cup 22 into the chamber 16 through an opening 24 in the chamber 16.

The injection system 12 fills the casting cavity 10 extremely quickly, within seconds or even milliseconds, and continues to apply pressure to the metal until the metal solidifies. The metal can be quickly cooled by means of a water cooling system, which comprises a series or network of water cooling pipes 26, extending through the mold halves 2, 3, in order to accelerate the solidification of the metal. After the metal has solidified, the movable plate 6 is retracted, separating the mold halves 2, 3 and opening the casting mold 100. The solidified casting can then be pushed out of the casting mold by means of ejector pins 28, which push the casting out of the mold half 3.

At this stage, the core 8 must still be contained within the casting. According to the present invention, the core 8 is made of a composition that disintegrates in water and can be easily removed from the casting by simply rinsing with water.

Examples

Example 1

The following sample compositions are initially prepared.

Table 1 Composition 1 2 3 4 5 Sand Quartz Quartz Quartz Quartz Quartz Composition of the binder Water ^a 29.6 50.9 43.6 43.5 Sucrose ^a 62.7 Sodium 4-(methoxycarbol)phenolate ^a 0,1 Sodium polyphosphate ^{a, c} (Budit 4H) 21.8 29.1 29.1 Sodium polyacrylate ^{a, d} (Dispex AA4135) 69.65 Dextrin ^{a, d}
(P623/4) 29.85 Carboxymethylcellulose ^a 7.6 13.65 13.65 13.65 Potato starch ^a (Honig) 13.65 13.65 13.65 Dodecylbenzenesulfonate ^a (Sermul EA88) 0,1 2-ethylhexylsulfosuccinate (Serwet WH175) 0.50 Total ^b 3.03 11.00 11.00 11.00 5.00 Pozzolanic additive Fly ash ^b (Microsit H10) 2.00 ^a - % by weight relative to the total weight of the binder composition, ^b - % by weight relative to the weight of sand, ^c - polymer chain length 30, ^d - aqueous solution, solids content 40% w/v.

A Laempe L1 laboratory core-throwing machine is used to produce hardened cores from each of the example compositions 1-5. The core-throwing machine is set with a blast time of 1-2 seconds and a blast pressure of 4 bar. If required, the cores are blasted with heated air at 120°C for 60-300 seconds. The core box temperature is set at 140°C. The cores are produced in generally cylindrical shape having a maximum diameter of 50 mm and an overall height of 80 mm, with a frustonic section of 30 mm at one end tapering to a minimum diameter of 40 mm. The example compositions are also used to produce cross beams having dimensions 180 x 22.4 x 22.4 mm for flexural strength measurements.

Cylindrical bars and cross beams made using Example Compositions 1-5 are tested for flexural strength and water solubility immediately after manufacture (as received) and after heating for 2 hours at 120, 140, 160, 180, 200, 220, or 240°C to simulate the range of temperatures to which the bar may be exposed in use.

The flexural strength of cross beams is measured using a three-point bending test at room temperature.

The water solubility of the rods is determined qualitatively by hanging the rod in a box, filling the box with water at room temperature until the rod is completely submerged, then draining the water from the box and observing how much of the suspended rod material disintegrates.

Example compositions 3-5 are also tested for flow using a Brookfield Powder Flow Tester. The unconfined fracture strength of the composition is measured at 0.60, 1.13, 2.19, 4.35, and 8.70 kPa.

The results are shown in Table 2.

Table 2 Composition 1 2 3 4 5 Bending strength N/ ^cm2 Immediately after production 120-140 270 304 269 372 120°C 60 225 183 225 278 140°C 20 215 143 177 297 160°C 10 200 149 204 228 180°C 100 175 136 208 261 200°C 120 230 124 192 286 220°C N/A N/A 119 196 238 240°C N/A N/A 95 182 260 Water solubility Immediately after production Excellent Excellent Excellent Excellent Excellent 120°C Excellent Excellent Excellent Excellent Excellent 140°C Excellent Excellent Excellent Excellent Excellent 160°C Good Excellent Excellent Excellent Excellent 180°C Bad Excellent Excellent Excellent Excellent 200°C Bad Excellent Excellent Excellent Excellent 220°C Bad Excellent Excellent Excellent Excellent 240°C Bad Excellent Excellent Excellent Excellent Fluidity 0.60 kPa N/A N/A 0.613 0.485 0.304 1.13 kPa N/A N/A 0.976 0.691 0.413 2.19 kPa N/A N/A 1,574 1,047 0.535 4.35 kPa N/A N/A 2,335 1.47 0.671 8.70 kPa N/A N/A 3,392 2,2 0.9075 Eco-friendly Yes No No No Yes

Exemplary composition 1, containing sucrose and carboxymethyl cellulose as hydrophilic polymers, achieves good water solubility up to 160°C. However, sucrose caramelized above 160°C radically reduces water solubility and the rods were relatively weak, with flexural strengths well below 200 N/cm ² .

Rods made using polyphosphate compositions, exemplary compositions 2-4, achieve excellent water solubility even after heating at temperatures up to 240°C for 2 hours and good flexural strength. Exemplary composition 4, which contains a small amount of surfactant but is otherwise identical to exemplary composition 3, shows increased flexural strength after heat treatment, as well as improved flowability.

Exemplary composition 5, containing sodium polyacrylate and dextrin as hydrophilic polymers together with a small amount of surfactant, achieves good flexural strength, water solubility and flowability (even after heating up to 240°C for 2 hours) and is also environmentally friendly. This composition is therefore selected as the basis for additional tests.

Example 2

Additional compositions are prepared based on exemplary composition 5, containing identical components and in identical amounts, but with varying proportions of sodium polyacrylate and dextrin.

Bars produced using these compositions are tested for flexural strength and yield strength using identical procedures as described in Example 1.

Water solubility is measured semi-quantitatively using a procedure similar to that described in Example 1. The rod is suspended in a box and the box is filled with water at room temperature until the rod is completely immersed. The rod is then gently shaken and the time required for complete disintegration of the rod is observed.

The results are shown in Tables 3a and 3b.

Table 3a Composition 6 7 8 9 10 Sodium polyacrylate ^{a, b} 0 10 20 30 40 Dextrin ^{a, b} 100 90 80 70 60 Bending strength N/ ^cm2 Immediately after production 228±19 235±12 268±9 310±7 295±6 Water solubility seconds Immediately after production 5-10 5-10 5-10 5-10 5-10 140°C 20-30 15-25 10-15 10-15 15-25 200°C 150-180 N/A N/A N/A N/A Fluidity 0.60 kPa 0,450 0.429 0.388 0.411 0.384 1.13 kPa 0.627 0,600 0.579 0,570 0.564 2.19 kPa 0.841 0,800 0.803 0.748 0.732 4.35 kPa 1,112 1,021 1,021 0.959 0.923 8.70 kPa 1,371 1,359 1,334 1,142 1,136 ^a - % by weight relative to the total weight of sodium polyacrylate and dextrin, ^b - aqueous solution, solids content 40% w/v.

Table 3b Composition 11 12 13 14 15 16 Sodium polyacrylate ^{a, b} 50 60 70 80 90 100 Dextrin ^{a, b} 50 40 30 20 10 0 Bending strength N/ ^cm2 Immediately after production 316±9 391±26 410±19 374±38 313±9 264±40 Water solubility seconds Immediately after production 5-10 10-15 10-15 20-25 10-15 20-30 140°C 5-10 5-10 20-30 20-30 20-25 20-25 200°C N/A 50-60 15-25 30-40 30-40 30-40 Fluidity 0.60 kPa 0.403 0.42 0.413 0.423 0.402 0.395 1.13 kPa 0.567 0.561 0.556 0.574 0.555 0.558 2.19 kPa 0.729 0.708 0.717 0.722 0.713 0.721 4.35 kPa 0.9 0.861 0.871 0.874 0.886 0.889 8.70 kPa 1,089 1,033 1,053 1,055 1,061 1,076 ^a - % by weight relative to the total weight of sodium polyacrylate and dextrin, ^b - aqueous solution, solids content 40% w/v.

Each of the rods made with exemplary compositions 6-16 exhibits reasonable flexural strength of at least 200 N/ ^cm2 . Rods containing 30-100 wt.% sodium polyacrylate exhibit good flexural strength of approximately ≥ 300 N/ ^cm2 , while rods containing 60-80 wt.% sodium polyacrylate, in particular, exhibit very good flexural strength of approximately ≥ 400 N/ ^cm2 .

Each of the rods shows very good water solubility immediately after manufacture. However, after heating for 2 hours at 200°C, the rods containing 10-50 wt.% sodium polyacrylate only weaken in water and do not disintegrate, so that these compositions should be suitable only for lower temperature applications. The rods containing 60-100 wt.% sodium polyacrylate show good water solubility even after heating for 2 hours at 200°C, while the rod containing 70 wt.% sodium polyacrylate shows very good water solubility.

Each of the compositions shows acceptable flowability, with compositions containing 50-100% by weight of sodium polyacrylate showing particularly good flowability.

A composition containing 70% by weight sodium polyacrylate (corresponding to example compositions 5 and 13) is selected as a basis for additional testing relative to several other binder combinations.

Example 3

The rods are prepared using the following compositions and tested for flexural strength and water solubility for the rods immediately after manufacture (without exposure to heat). Flexural strength is tested using the same technique as described in Example 1.

Water solubility is measured quantitatively. A large beaker is placed on a balance set and the balance is tared. A rod is mounted on the end of the rotor shaft and lowered into the beaker so that the rod hangs above the base of the beaker and is not weighed by the balance. The container is then filled with water to completely submerge the rod, and the rod is rotated on the rotor shaft to stir the water. The weight displayed on the balance is observed to determine the time required for the rod to completely disintegrate and fall into the container. This experiment is performed under two different conditions: 1) a stirring speed of 60 rpm and a water temperature of 20°C; and 2) a stirring speed of 150 rpm and a water temperature of 65°C.

The results are shown in Table 4.

Table 4 Composition 17 18 19 20 21 Sand Quartz Quartz Quartz Quartz Quartz Composition of the binder Water ^a 4.5 Sodium polyacrylate ^{a, d} (Dispex AA4135) 69.65 Dextrin ^{a, d} (P623/4) 29.85 Sodium silicate/lithium silicate ^{a, f} (ZSE 874) 90.0 Potassium silicate ^{a, f} (K-silicate 42/43) 5.0 Formaldehyde phenol^a(Politec E 6010) 50.0 Isocyanic acid, polyethylene polyphenylene ether ^a (Politec E 9030) 50.0 Acid Catalyst ^a (Cataset ST2) 23.1 Furfuryl alcohol ^a (Eshanol U1N) 76.9 Polyvinyl alcohol ^{a, e} (P118/2) 74.1 Glycerin ^a (Glysorb 14) 1.5 Sorbitol ^{a, d} (Glysorb 14) 5.9 Potato starch ^a 18.5 Sodium 2-ethylhexyl sulfate ^a (DSK 40) 0.5 2-ethylhexylsulfosuccinate ^a (Serwet WH175) 0.50 Total ^b 10.0 4.0 1.6 2.16 10.8 Pozzolanic additive Quartz dust ^c (Quartz dust A by Cofermin) 100,0 68.0 100,0 Aluminum silicate ^c (Eurocell 150H) 6.8 Carbon black ^c 0.2 Silicon dioxide/kaolinite ^c (EM Aktisil) 25.0 Total ^b 8.0 0.8 0,0 0,0 8.0 Bending strength N/ ^cm2 Immediately after production 829±27 794±18 335±9 287±1 798±8 Water solubility seconds 20°C, 60 rpm 20-40 N/A (>60 min) N/A (>60 min) N/A (>60 min) 240-260 65°C, 150 rpm 5-15 N/A (>60 min) N/A (>60 min) N/A (>60 min) 15-45 ^a - % by weight relative to the total weight of the binder composition, ^b - % by weight relative to the weight of the sand, ^c - % by weight relative to the total weight of the pozzolanic additive, ^d - aqueous solution, solids content of 40% w/v, ^e - aqueous solution, solids content of 20% w/v, ^f - aqueous solution, solids content of 35-45% w/v.

The bars produced using compositions 17, 18 and 21 show excellent flexural strength of approximately 800 N/ ^cm2 .

The rods made using compositions 18-20 do not show water solubility, even when stirred at 65°C and 150 rpm, so these compositions are considered unsuitable for use in the present invention. Composition 21 shows acceptable water solubility, while composition 17 shows excellent water solubility.

Composition 17 is based on Compositions 5 and 13, with quartz dust used in place of fly ash and an increased amount of binder composition and pozzolanic additive used. These changes result in a doubling of flexural strength compared to Compositions 5 and 13, without significant loss of water solubility or flowability. Bars made using Composition 17 are free of defects and exhibit excellent, homogeneous compaction.

The water solubility of compositions 17 and 21 is further tested after heating the rods for 30 minutes at 200, 300 and 400°C, with a water temperature of 65°C and a rotation speed of 150 rpm. The results are shown in Table 5.

Table 5 Composition Immediately after production 200°C 300°C 400°C 17 5-15 sec 5-15 sec 5-15 sec 20-120 sec 21 15-45 sec 30-240 s N/A (>300 sec) N/A (>300 sec)

The rods made using composition 17 show good water solubility even after heating up to 400°C. The rods made using composition 21 show good water solubility after heating up to 200°C, but the rods heated up to 300 and 400°C show no signs of significant disintegration after 300 s of water stirring.

Example 4

The effect of varying the relative content of binder and pozzolanic additive on the strength of the rods is investigated. The rods are prepared using the following compositions and tested for flexural strength and water solubility for the rods immediately after manufacture (without exposure to heat). Flexural strength is tested using the identical technique described in Example 1.

The binder used in each of the following compositions is as described in composition 17 above: sodium polyacrylate at 69.65% (Dispex AA4135); dextrin at 29.85% (P623/4); and 2-ethylhexyl sulfosuccinate at 0.5% (Serwet WH175). Percentages are wt. % relative to the total weight of the binder composition. The results are shown in Tables 6a and 6b (composition 26 is listed twice for ease of comparison).

Table 6a shows the effect of varying the pozzolanic additive content. It is found that increasing the pozzolanic additive content results in bars with higher flexural strength. Composition 23, which does not contain pozzolanic additive, is significantly weaker than even 2% pozzolanic additive based on sand weight. Compositions 22 and 26 show that the particular choice of pozzolanic additive has an effect on flexural strength, but that the required strength is not limited to a single pozzolanic additive.

Table 6a Composition 22 23 24 25 26 Refractory material Quartz sand (H33) Content of the binder ^a 6 6 6 6 6 Pozzolanic additive Fly ash - Quartz dust A Quartz dust A Quartz dust A Content of pozzolanic additive ^a 6 0 2 4 6 Bending strength N/ ^cm2 Immediately after production 547±22 110±7 694±20 1040±41 1332±29 ^a - % by weight relative to the weight of the refractory material

Table 6b Composition 27 28 29 30 26 Refractory material Quartz sand (H33) Content of the binder ^a 2 3 4 5 6 Content of pozzolanic additive ^{a, b} 6 6 6 6 6 Bending strength N/ ^cm2 Immediately after production 71±4 435±15 809±22 1056±37 1332±29 ^a - % of mass relative to the mass of refractory material; ^b - Quartz dust A

Table 6b shows that increasing the binder content (e.g., hydrophilic polymer content), relative to the weight of refractory material, results in an increase in the flexural strength of the bars. Compositions having very low binder content are found to be significantly weaker, despite the relatively high content of pozzolanic additive. Compositions 22-30 are all found to have acceptable water solubility.

Claims (44)

1. A composition for the manufacture of a rod used in the process of molding or casting metals, comprising: - refractory material in the form of particles, - a binder composition comprising at least one hydrophilic polymer, wherein the at least one hydrophilic polymer comprises at least one polysaccharide or polysaccharide derivative, and - at least one pozzolanic additive. 2. The composition according to claim 1, wherein the composition comprises at least 1 wt. % of the binder composition and at least 1 wt. % of the pozzolanic additive relative to the weight of the refractory material. 3. The composition according to claim 1 or 2, wherein at least one hydrophilic polymer comprises at least one synthetic polymer. 4. The composition according to claim 3, wherein at least one synthetic polymer is selected from the group consisting of polyacrylates, polymethacrylates, polyphosphates, polymetaphosphates, polyvinyl alcohol, alkaline polyacrylate salts, alkaline polyphosphate salts and mixtures thereof. 5. The composition according to any one of claims 2 to 4, wherein at least one synthetic polymer has a molecular weight of no more than 1,000,000 g/mol. 6. The composition according to any one of claims 1-5, wherein at least one polysaccharide or polysaccharide derivative is selected from the group consisting of: starch, starch derivatives, potato starch, dextrin cellulose, cellulose derivatives, carboxymethyl cellulose and mixtures thereof. 7. The composition according to any one of claims 1 to 6, wherein at least one hydrophilic polymer is in solution and, optionally, wherein the solution of the hydrophilic polymer is an aqueous solution. 8. The composition according to claim 7, wherein the solution of the hydrophilic polymer has a solids content of 10-80 wt.%/vol. 9. The composition according to any one of claims 1 to 8, wherein the binder composition has a dynamic viscosity at 23°C of 5 mPa⋅s to 1 Pa⋅s. 10. The composition according to any one of claims 1 to 9, wherein at least one hydrophilic polymer does not undergo crosslinking when the composition is heated to a temperature of from 200 to 350°C. 11. The composition according to any one of claims 1 to 10, wherein the binder composition additionally contains at least one plasticizer. 12. The composition of claim 11, wherein the at least one plasticizer comprises at least one polyol or polyol derivative and, optionally, wherein the at least one plasticizer is selected from the group consisting of glycerol, sorbitol, xylitol, malitol, triacetin and mixtures thereof. 13. The composition according to any one of claims 1-12, further comprising at least one surfactant. 14. The composition according to claim 13, wherein at least one surfactant is selected from the group consisting of: anionic, cationic, nonionic and amphoteric surfactants, sulfates, methosulfates, linear alcohol sulfates, sulfonates, sulfosuccinates, phosphate esters, glucosides and mixtures thereof. 15. The composition according to claim 13 or 14, wherein at least one surfactant is selected from the group consisting of: 2-ethylhexyl sulfosuccinate, 2-ethylhexyl sulfate, dodecylbenzenesulfonate, nonylphenol sulfate, sodium laureth sulfate, 3-ethylhexyl phosphate ether, undecylamidopropyltrimethylammonium methosulfate, ammonium methosulfate based on alkyl polyglycol ether, 2-ethylhexyl glucoside, hexyl glucoside and mixtures thereof. 16. The composition according to any one of claims 1 to 15, wherein at least one pozzolanic additive is selected from the group consisting of: quartz dust, fly ash, rice husk ash, diatomaceous earth, volcanic ash, metakaolin and mixtures thereof. 17. The composition according to any one of claims 1 to 16, wherein at least one pozzolanic additive comprises spherical particles and/or cenospheres. 18. The composition according to any one of claims 1 to 17, wherein at least one pozzolanic additive has a particle diameter D50 of no more than 20 μm. 19. The composition according to any one of claims 1 to 18, wherein the refractory particulate material comprises one or more of: sand, quartz sand, spherical particles and/or cenospheres, and fly ash. 20. The composition according to any one of claims 1 to 19, wherein the refractory material in the form of particles has a particle diameter D50 of at least 50 μm. 21. A rod for molding or casting molten metals, containing a composition according to any one of claims 1-20. 22. The rod according to claim 21, wherein the rod is provided with a surface coating and, optionally, the surface coating comprises boron nitride, silicate, titanium dioxide, aluminum oxide, zirconium dioxide or mixtures thereof. 23. A casting mold for producing an article by casting metals, containing a core according to item 21 or 22, wherein the core is designed with the possibility of defining an internal cavity of the article. 24. The casting mold according to item 23, wherein the casting mold is designed with the possibility of high-pressure casting or semi-solid pressure casting. 25. A casting mould according to claim 23 or 24, wherein the hardened core composition degrades in water such that a cylinder of the hardened core composition, having a maximum height of 80 mm and a maximum diameter of 50 mm, disintegrates in less than 10 minutes when immersed in water at a temperature of 20°C and stirred at a rotation speed of 60 rpm, and - wherein the hardened composition of the said rod has a bending strength of at least 300 N/cm ² . 26. The casting mold according to claim 25, wherein the cylinder of the hardened composition of said core disintegrates in water in less than 10 minutes after heating to a temperature of from 200 to 350°C. 27. A method for manufacturing an article by high pressure casting or semi-solid pressure casting, the method comprising the steps of: (i) mixing the composition according to any one of claims 1 to 18 to obtain a mixture, (ii) molding and curing the mixture to form a core in the shape of the internal cavity of the article, (iii) assemble the core with a casting mold for high-pressure casting of metals or semi-solid pressure casting of metals to provide a casting cavity, (iv) inject molten or semi-solid metal into the casting cavity until it is filled, (v) cool and solidify the molten or semi-solid metal to form a product in the internal cavity of which a rod is placed, (vi) remove the product with the core from the casting mould, (vii) remove the rod from the internal cavity by rinsing with water. 28. The method of claim 27, further comprising the step of applying a surface coating to the rod prior to assembling the rod with the casting mold. 29. The method according to claim 27 or 28, wherein the step of molding and curing the mixture includes a step in which the mixture is dried. 30. The method according to any one of claims 27-29, in which the step of molding and curing the mixture includes a step in which the mixture is compacted into a mold. 31. The method according to any one of paragraphs 27-30, in which the stage of molding and curing the mixture is performed using sand-throwing rod equipment. 32. The method according to any one of claims 27-31, in which the step of molding and curing the mixture to ensure the production of the rod includes the step of producing the rod by means of an additive manufacturing process or three-dimensional printing. 33. Use of a composition according to any one of paragraphs 1-20 as a composition for producing a rod used in the process of molding or casting metals.