Molding sand additive package

Abstract

The present invention discloses molding sand additive packages, molding sand binder compositions comprising the molding sand additive packages, molding sand comprising the molding sand binder compositions, use of the molding sand and a method of sand casting.

Description

[0001] MOLDING SAND ADDITIVE PACKAGE

[0002] FIELD OFTHE INVENTION

[0003]

[0001] The present invention relates to molding sand additive packages, molding sand binder compositions comprising the molding sand additive packages, molding sand comprising the molding sand binder compositions, use of the molding sand and a method of sand casting.

[0004] BACKGROUND OFTHE INVENTION

[0005]

[0002] Molding sand is used in the process of sand casting to provide a mold cavity, which can be used in the casting of materials such as metals or metal alloys. Molding sand is useful in the process of casting, for example casting metal, as when moistened and compressed or heated, it packs well and maintains its shape. Molding sands typically comprise aggregate / sand material, binder material and additive species. The binder material is added to improve the binding of the aggregate or sand, which helps the aggregate or sand maintain its shape. Additive species are typically added in order to improve one or more properties of the molding sand. For example, additive species may be added to molding sand with the aim of providing a mold with suitable properties (e.g., mechanical strength, processibility, workability and ease of shake out) and improving casting quality (e.g., by decreasing surface and / or expansion defects).

[0006]

[0003] A traditional additive in molding sand are species known as lustrous carbon formers (LCF), such as coal, or petroleum resin e.g., hydrocarbon resin. Coal has traditionally been used as an additive in molding sand to help achieve good casting quality, including helping to reduce surface and expansion defects, while also aiding separation of the castings and the mold. However, the environmental impact of some LCF species, such as coal, or petroleum resin e.g., hydrocarbon resin, is a concern. Therefore, the reduction of organic carbonaceous additives derived from fossil fuel sources is desired.

[0004] There is a need to provide alternative additive(s) for molding sand, which can provide good mold quality and / or good casting quality and have reduced environmental impact.

[0007] SUMMARY OF THE INVENTION

[0008]

[0005] The present invention is defined in the appended claims.

[0009]

[0006] In accordance with a firstaspect, there is provided a molding sand additive package comprising a graphite composition, an illite composition and a polysaccharide composition.

[0010]

[0007] The illite composition may comprise or may be a deagglomerated illite composition. The illite composition may have a median particle size, d5o, of about 100 pm or less, for example, about 50 pm or less. The illite composition may comprise at least about 50 wt.% illite based on the total weight of the illite composition.

[0011]

[0008] The graphite composition may comprise or may be a macrocrystalline graphite.

[0012]

[0009] The polysaccharide composition may comprise or may be starch. The starch may be a pre-gelatinised starch.

[0013]

[0010] The molding sand additive package may be essentially free of coal.

[0014] The graphite composition, illite composition and polysaccharide composition may be present in a weight ratio of 1 :3:3 to 1 :5:10 polysaccharide composition:graphite composition:illite composition. In other words, the graphite composition, illite composition and polysaccharide composition may be present in a weight ratio of 3:3:1 to 5:10:1 of graphite compositiomillite composition:polysaccharide composition.

[0015]

[0011] In accordance with a second aspect, there is provided a molding sand binder composition comprising the molding sand additive package according to the first aspect and a binding agent.

[0016]

[0012] The binding agent may comprise or may be a clay or clay containing material such as smectite; montmorillonite; hectorite; saponite; nontronite, beidellite; sauconite; ball clay; fire clay; laponite; bentonite; kaolinite; chlorite or a combination thereof. The binding agent may comprise or may be bentonite.

[0013] The graphite composition may be present in the molding sand binder composition in an amount of about 1 wt.% to about 25 wt.%, based on the total weight of the molding sand binder composition.

[0017]

[0014] The illite composition may be present in the molding sand binder composition in an amount of about 2 wt.% to about 40 wt.%, based on the total weight of the molding sand binder composition.

[0018]

[0015] The polysaccharide composition may be present in the molding sand binder composition in an amount of about 0.25 wt.% to about 10 wt.%, based on the total weight of the molding sand binder composition.

[0019]

[0016] The graphite composition may be present in the molding sand binder composition in an amount of about 1 wt.% to about 25 wt.%, the illite composition may be present in the molding sand binder composition in an amount of about 2 wt.% to about 40 wt.%, the polysaccharide composition may be present in the binder composition in an amount of about 0.25 wt.% to about 10 wt.%, and the remainder of the binder composition may be bentonite. For example, the binder may present in an amount of about 35 wt.% to about 93.75 wt.%, based on the total weight of the molding sand binder composition. The binder may be bentonite.

[0020]

[0017] In accordance with a third aspect, there is provided a molding sand comprising an aggregate and the molding sand binder composition according the second aspect.

[0021]

[0018] The aggregate may be selected from silica sand, zirconia sand, chromite sand, quartz sand, non-silica synthetic sand, aluminosilicates or combinations thereof. The silica sand may be natural silica sand and / or synthetic silica sand.

[0022]

[0019] In accordance with a fourth aspect, there is provided a use of a molding sand according to the third aspect to form a casting mold.

[0023]

[0020] In accordance with a fifth aspect, there is provided a use of a molding sand additive package according the first aspect, to reduce casting defects in molding sand.

[0024]

[0021] In accordance with a sixth aspect, there is provided a method of sand casting comprising: blending the molding sand additive package according to the first aspect with a binding agent, to provide a molding sand binder composition; blending the molding sand binder composition with an aggregate to provide a molding sand; mixing the molding sand with water; and preparing a mold by forming the molding sand and water mixture into a shape.

[0025]

[0022] The method may further comprise: introducing a metal or metal alloy into the mold to form a casted article; and removing the casted article from the mold. The metal or metal alloy may be molten. The molding sand may be recycled in further casting processes.

[0026]

[0023] Certain embodiments of the present invention may provide one or more of the following advantages:

[0027] • possibility of partial or full replacement of lustrous carbon formers, such as coal, or petroleum resin e.g., hydrocarbon resin, in a molding sand by a molding sand additive package according to the present disclosure;

[0028] • molding sand with low emissions, in particular carbonaceous emissions such as CO, CO2, light hydrocarbons, and BTEX (benzene, toluene, ethylbenzene, xylene) compounds;

[0029] • molding sand able to provide good flowability;

[0030] • molding sand with suitable sintering behaviour

[0031] • molding sand with a suitable moisture content;

[0032] • molding sand able to provide suitable permeability when compacted;

[0033] • molding sand able to provide product with high compaction when compacted;

[0034] • molding sand able to provide high strength when compacted;

[0035] • molding sand able to provide good casting quality;

[0036] • molding sand cast to provide product with suitably low casting defects, such as surface and expansion defects;

[0037] • molding sand comprising readily available additives, that may be, for example, locally sourced;

[0038] • desired reduction of carbon footprint.

[0024] The details, examples and preferences provided in relation to any particular one or more of the stated aspects of the present invention apply equally to all aspects of the present invention. Any combination of the embodiments, examples and preferences described herein in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein, or otherwise clearly contradicted by context.

[0039]

[0025] It is understood that the following description concerns exemplary embodiments of the present invention and shall not be limiting to the scope of the claims.

[0040] DETAILED DESCRIPTION

[0041]

[0026] The present invention is based on the surprising finding that the molding sand additive package disclosed herein can produce molding sands with good mechanical properties whilst replacing LCFs, such as coal. In accordance with a first aspect, there is provided a molding sand additive package comprising a graphite composition, an illite composition and a polysaccharide composition. The molding sand additive package balances the properties of its additive components with an aim to provide optimal molding sand properties, for example optimal mechanical properties, emissions, and casting quality.

[0042]

[0027] A “molding sand additive package” refers to a combination of one or more additive species that may be added to a molding sand. The molding sand additive package may therefore also be referred to as a molding sand additive combination or molding sand additive composition. A molding sand is suitable to form a casting mold. In addition to a molding sand additive package, the molding sand may comprise a binder and an aggregate. Some examples of additive species of the molding sand additive package are a graphite composition, an illite composition and a polysaccharide composition. The molding sand additive package of the present disclosure may provide one or more properties, characteristics or advantages to the molding sand.

[0043]

[0028] Without wishing to be bound by theory, it is believed that the presence of the illite composition in the molding sand additive package helps to maintain the sintering temperature of the molding sand. The illite composition also has a high chemical and thermal stability, and so has low mass loss and low emission levels during the casting process. It is also considered that the illite composition may beneficially absorb excess moisture in the molding sand, without swelling.

[0044]

[0029] The illite composition may comprise or may be a deagglomerated illite composition. In some examples, illite composition does not comprise a deagglomerated illite. The illite composition may have a d5o of about 100 pm or less, for example, about 75 pm or less, or about 50 pm or less, or about 25 pm or less, or about 10 pm or less, or about 5 pm or less, or about 2.5 pm or less, or about 1 .5 pm or less, or about 1 pm or less, or about 0.5 pm or less, or about 0.25 pm or less, or about 0.1 pm or less. The illite composition may have a d5o of from about 0.1 pm to about 50 pm, for example, from about 0.5 pm to about 25 pm, or from about 1 pm to about 10 pm, or from about 1 .5 pm to about 5 pm, or from about 2 pm to about 5 pm. The illite composition may have a d95of about 500 pm or less, for example, about 400 pm or less, or about 300 pm or less, or about 200 pm or less, or about 100 pm or less, or about 75 pm or less, or about 50 pm or less, or about 25 pm or less, or about 10 pm or less, or about 1 pm or less. The illite composition may have a d95of from about 10 pm to about 200 pm, or from about 20 pm to about 100 pm, or from about 30 pm to about 50 pm, or from about 35 pm to about 45 pm.

[0045]

[0030] Particle size properties referred to herein, such as the d5o median particle size, or d95particle size, are measured by wet Malvern laser scattering (standard ISO 13320-1). In this technique, the size of particles in powders, suspensions and emulsions may be measured using the diffraction of a laser beam, based on the application of Mie theory. Such a machine, for example a Malvern Mastersizer 2000 (as supplied by Malvern instruments) provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the “equivalent spherical diameter” (e.s.d), less than given e.s.d values. The mean particle size d5o is the value determined in this way of the particle e.s.d. at which there are 50% by weight of the particles which have an equivalent spherical diameter less than that d5o value. For the avoidance of doubt, the measurement of particle size using laser light scattering is not an equivalent method to a sedimentation method.

[0046]

[0031] The illite composition may comprise at least about 50 wt.% illite, based on the total weight of the illite composition. For example, at least about 55 wt.% illite, or about 60 wt.% illite, or at least about 65 wt.% illite, or at least about 70 wt.% illite, or at least about 75 wt.% illite, or at least about 80 wt.% illite, or at least about 85 wt.% illite, or at least about 90 wt.% illite, or at leastabout 95 wt.% illite, or at least about 99 wt.% illite, based on the total weight of the illite composition. In some examples the amount of illite may be about 50 wt.%, or about 60 wt.%, or about 65 wt.%, or about 70 wt.%, or about 75 wt.%, or about 80 wt.%, or about 85 wt.%, or about 90 wt.%, or about 95 wt.%, or about 100 wt.%, based on the total weight of the illite composition. The illite composition may comprise from about 50 wt.% to about 95 wt.% illite, or from about 55 wt.% to about 80 wt.% illite, or from about 60 wt.% to about 85 wt.% illite, or from about 65 wt.% to about 80 wt.% illite, based on the total weight of the illite composition.

[0047]

[0032] The illite composition may comprise one or more further chemical species. The illite composition may comprise one or more further mineral species. The further mineral species may be, but is not limited to, for example, one or more of kaolinite, calcite, smectite, montmorillonite, chlorite, apatite, Ti-containing minerals, quartz, feldspar, halloysite, sericite, muscovite, mixed-layers or the like. In some examples, the illite composition does not comprise one or more further mineral species. The illite composition may comprise trace amounts of one or more further mineral species. The illite composition may comprise about 5 wt.% of one or more further mineral species, for example, about 10 wt.% of one or more further mineral species, or about 15 wt.% of one or more further mineral species, or about 20 wt.% of one or more further mineral species, or about 25 wt.% of one or more further mineral species, or about 30 wt.% of one or more further mineral species, or about 35 wt.% of one or more further mineral species, or about 40 wt.% of one or more further mineral species, or about 45 wt.% of one or more further mineral species, or about 50 wt.% of one or more further mineral species, based on the total weight of the illite composition. The illite composition may comprise from about 5 wt.% to about 50 wt.% of one or more further mineral species, or from about 10 wt.% to about 40 wt.% of one or more further mineral species, or from about 15 wt.% to about 30 wt.% of one or more further mineral species, based on the total weight of the illite composition.

[0048]

[0033] The illite composition may further comprise kaolinite, calcite, smectite, montmorillonite, chlorite, apatite, Ti-containing minerals, quartz, feldspar, halloysite, sericite, muscovite, mixed-layers or the like. The illite composition may comprise kaolinite. The illite composition may comprise calcite. The illite composition may comprise smectite. The illite composition may comprise montmorillonite. The illite composition may comprise quartz. The illite composition may comprise feldspar. The illite composition may comprise from about 1 wt.% to about 20 wt.% kaolinite, or from about 2.5 wt.% to about 17.5 wt.% kaolinite, or from about 5 wt.% to about 15 wt.% kaolinite, or from about 7.5 wt.% to about

[0049] 12.5 wt.% kaolinite, based on the total weight of the illite composition. The illite composition may comprise about 20 wt.% kaolinite, or about 15 wt.% kaolinite, or about 10 wt.% kaolinite, or about 5 wt.% kaolinite, or a bout 1 wt.% kaolinite, based on the total weight of the illite composition. The illite composition may comprise from about 1 wt.% to about 20 wt.% calcite, or from about 2.5 wt.% to about 17.5 wt.% calcite, or from about 5 wt.% to about 15 wt.% calcite, or from about 7.5 wt.% to about 12.5 wt.% calcite, based on the total weight of the illite composition. The illite composition may comprise about 20 wt.% calcite, or about 15 wt.% calcite, or about 10 wt.% calcite, or about 5 wt.% calcite, or about 1 wt.% calcite, based on the total weight of the illite composition. The illite composition may comprise from about 1 wt.% to about 20 wt.% smectite, or from about 2.5 wt.% to about

[0050] 17.5 wt.% smectite, or from a bout 5 wt.% to about 15 wt.% smectite, or from about 7.5 wt.% to about 12.5 wt.% smectite, based on the total weight of the illite composition. The illite composition may comprise about 20 wt.% smectite, or about 15 wt.% smectite, or about 10 wt.% smectite, or about 5 wt.% smectite, or about 1 wt.% smectite, based on the total weight of the illite composition. The illite composition may comprise from about 1 wt.% to about 20 wt.% montmorillonite, or from about 2.5 wt.% to about 17.5 wt.% montmorillonite, or from about 5 wt.% to about 15 wt.% montmorillonite, or from about 7.5 wt.% to about

[0051] 12.5 wt.% montmorillonite, based on the total weight of the illite composition. The illite composition may comprise about 20 wt.% montmorillonite, or about 15 wt.% montmorillonite, or about 10 wt.% montmorillonite, or about 5 wt.% montmorillonite, or about 1 wt.% montmorillonite, based on the total weight of the illite composition. The illite composition may comprises trace amounts of quartz. The illite composition may comprise trace amounts of feldspar. Trace amounts refers to about 2 wt.% of the illite composition or less, based on the total weight of the illite composition.

[0052]

[0034] In some examples, the illite composition is obtained by mecha nical treatment of the illite composition, deagglomeration of pre-crushed material using high acceleration, producing a fluidized bed to impact the agglomerates with each other and with an impact surface.

[0053]

[0035] Without wishing to be bound by theory, it is believed that the presence of the graphite composition in the molding sand additive package helps to prevent casting defects by increasing compaction of the mold to avoid metal-mold interactions. The graphite composition also has high chemical and thermal stability, and so has low mass loss and low emission levels during the casting process, compared to other carbonaceous species.

[0054]

[0036] The graphite composition may comprise at least about 70 wt.% graphite, based on the total weight of the graphite composition. For example, at least about 75 wt.% graphite, or at least about 80 wt.% graphite, or at least about 85 wt.% graphite, or at least about 90 wt.% graphite, or at least about 95 wt.% graphite, or at least about 99 wt.% graphite, based on the total weight of the graphite composition. In some examples the amount of graphite may be about 70 wt.%, or about 75 wt.%, or about 80 wt.%, or about 85 wt.%, or about 90 wt.%, or about 95 wt.%, or about 100 wt.%, based on the total weight of the graphite composition. The graphite composition may have a carbon content of about 70 wt.%, or about 75 wt.%, or about 80 wt.%, or about 85 wt.%, or about 90 wt.% or about 95 wt.%, based on the total weight of the graphite composition. The graphite composition may have a carbon content of from about 75 wt.% to about 95 wt.%, or from about 80 wt.% to about 90 wt.%, or from about 80 wt.% to about 85 wt.%. The graphite composition may have a median particle size, d5o, of about 500 pm or less, for example, about 450 pm or less, or about 400 pm or less or about 350 pm or less, or about 300 pm or less, or about 250 pm or less, or about 200 pm or less, or about 150 pm or less, or about 100 pm or less, or about 90 pm or less, or about 80 pm or less, or about 70 pm or less, or about 60 pm or less, or about 50 pm or less, or about 40 pm or less, or about 30 pm or less, or about 20 pm or less, or about 10 pm or less.

[0055]

[0037] The graphite composition may comprise or may be graphite. The graphite composition may comprise or may be a macrocrystalline graphite and microcrystalline graphite or combinations thereof. The graphite composition may comprise or may be microcrystalline graphite. The graphite composition may comprise or may be macrocrystalline graphite. Macrocrystalline graphite may have a crystallite size of more than about 65 nm, or more than about 75 nm, or more than about 85 nm, or more than about 95 nm, or more than about 100 nm, or more than about 110 nm, or more than about 120 nm, or more than about 140 nm, or more than about 160 nm, or more than about 180 nm, or more than about 200 nm or more than about 220 nm, or more than about 240 nm, or more than about 260 nm, or more than about 280 nm, or from about 65 nm to about 300 nm, or from about 75 nm to about 250 nm, or from about 100 nm to about 150 nm. Microcrystalline graphite may have a crystallite size of less than about 60 nm, or less than about 55 nm, or less than about 50 nm, or less than about 45 nm, or less than about 40 nm, or less than about 35 nm, or less than about 30 nm, or less than about 25 nm, or less than about 20 nm, or less than about 10 nm, or less than about 5 nm, or from about 1 nm to about 60 nm, or from about 5 nm to about 50 nm, or from about 10 nm to about 40 nm, or from about 20 nm to about 30 nm. The graphite composition may comprise or may be synthetic graphite. The graphite composition may be unmodified, i.e., the graphite composition may not undergo modification, for example, chemical modification. The graphite composition may be free of modification, for example, chemical modification.

[0056]

[0038] Without wishing to be bound by theory, it is believed that the presence of the polysaccharide composition in the molding sand additive package may help to prevent casting defects by providing similar decomposition properties to LCF species such as coal. Compared to the illite and graphite compositions, the polysaccharide composition is chemically and thermally reactive. The polysaccharide composition loses mass in a similar temperature range to coal. This behaviour is believed to relieve stress in the molding sand at the quartz expansion temperature, the temperature at which the quartz of the molding sand changes from a-quartz to 0-quartz, which causes a linear expansion of the material. It is believed that this stress relief reduces the likelihood of expansion defects. Further, the solubility of the polysaccharide composition in water is believed to increase the plasticity of the molding sand, which reduces tension duringthe casting process.

[0057]

[0039] The polysaccharide composition may be a polysaccharide. The polysaccharide composition may comprise at least about 70 wt.% polysaccharide, based on the total weight of the polysaccharide composition. For example, at least about 75 wt.% polysaccharide, or at least about 80 wt.% polysaccharide, or at least about 85 wt.% polysaccharide, or at least about 90 wt.% polysaccharide, or at least about 95 wt.% polysaccharide, or at least about 99 wt.% polysaccharide, based on the total weight of the polysaccharide composition. In some examples the amount of polysaccharide may be about 70 wt.%, or about 75 wt.%, or about 80 wt.%, or about 85 wt.%, or about 90 wt.%, or about 95 wt.%, or about 100 wt.%, based on the total weight of the polysaccharide composition.

[0058]

[0040] The polysaccharide composition may comprise or may be a natural polysaccharide, a synthetic polysaccharide or combinations thereof. The polysaccharide composition may comprise or may be starch, for example pre-gelatinised starch, amylose, amylopectin, glycogen, cellulose, dextrin, or the like. The polysaccharide composition may comprise or may be starch. The polysaccharide composition may comprise or may be pre-gelatinised starch.

[0059]

[0041] The molding sand additive package may be free or essentially free of fossil fuel species or species derived from fossil fuels. The molding sand additive package may be free or essentially free of coal, or petroleum resin e.g., hydrocarbon resin. The molding sand additive package may be free or essentially free of coal and petroleum resin e.g., hydrocarbon resin As used herein, “essentially free of coal and / or petroleum resin e.g., hydrocarbon resin” may mean less than 2 wt.%, less than 1 .5 wt.%, less than 1 .0 wt.%, less than 0.5 wt.%, less than 0.3 wt.%, less than 0.2 wt.%, less than 0.1 wt.%, less than 0.05 wt.%, or less than 0.01 wt.% coal and / or petroleum resin e.g., hydrocarbon resin, based on the total weight of the molding sand additive package. The molding sand additive package may comprise reduced levels of fossil fuel species or species derived from fossil fuels. The molding sand additive package may comprise reduced levels of coal. For example, the molding sand additive package may comprise less than 95 wt.%, less than 90 wt.%, less than 85 wt.%, less than 80wt.%, less than 75 wt.%, less than 70 wt.%, less than 65 wt.%, less than 60 wt.%, less than 55 wt.%, less than 50 wt.%, less than 45 wt.%, less than 40 wt.%, less than 35 wt.%, less than 30 wt.%, less than 25 wt.%, less than 20 wt.%, less than 15 wt.%, less than 10 wt.%, or less than 5.0 wt.% of coal, based on the total weight of the molding sand additive package. The molding sand additive package may comprise reduced levels of petroleum resin e.g., hydrocarbon resin. For example, the molding sand additive package may comprise less than 15 wt.%, less than 12.5 wt.%, less than 10 wt.%, less than 7.5 wt.%, less than 5 wt.%, less than 2.5 wt.% petroleum resin, e.g., hydrocarbon resin, based on the total weight of the molding sand additive package,

[0042] The molding sand additive package may comprise from about 15 wt.% to about 80 wt.% of the illite composition, based on the total weight of the molding sand additive package. For example, the illite composition may be present in an amount from about 20 wt.% to about 80 wt.%, or about 25 to about 80 wt.%, or about 30 wt.% to about 80 wt.%, or about 35 wt.% to about 75 wt.%, or from about 40 wt.% to from about 70 wt.%, or from about

[0060] 45 wt.% to about 65 wt.%, or from about 50 wt.% to about 60 wt.%, or from about 50 wt.% to about 55 wt.%, based on the total weight of the molding sand additive package.

[0061]

[0043] The molding sand additive package may comprise from about 5 wt.% to about 60 wt.% of the graphite composition, based on the total weight of the molding sand additive package. For exam pie, the graphite composition may be present in an amount of from about 10 wt.% to about 55 wt.%, or from about 15 wt.% to about 50 wt.%, or from about 20 wt.% to about 45 wt.%, or from about 25 wt.% to about 40 wt.%, or from about 30 wt.% to about 40 wt.%, or from about 30 wt.% to about 35 wt.%, based on the total weight of the molding sand additive package.

[0062]

[0044] The molding sand additive package may comprise from about 1 wt.% to about 35 wt.% of the polysaccharide composition, based on the total weight of the molding sand additive package. For example, the polysaccharide composition may be present in an amount of from about 2.5 wt.% to about 30 wt.%, or from about 5 wt.% to about 25 wt.%, or from about 7.5 wt.% to about 20 wt.%, or from about 10 wt.% to about 15 wt.%, based on the total weight of the molding sand additive package.

[0063]

[0045] The graphite composition, illite composition and polysaccharide composition may be present in a weight ratio of 1 :3:3 to 1 :5:10 polysaccharide composition:graphite compositiomillite composition, for example, 1 :3:4 to 1 :4:10 polysaccharide composition:graphite composition:illite composition, 1 :1.5:2 to 1 :5:10 polysaccharide composition:graphite composition:illite composition, 1 :2.5:4 to 1 :4:10 polysaccharide composition:graphite compositiomillite composition, 1 :3:4 to 1 :4:9 polysaccharide composition:graphite compositiomillite composition, 1 :2:2 to 1 :4:9 polysaccharide compositiomgraphite compositiomillite composition, 1 :1.5:2 to 1 :4:8 polysaccharide compositiomgraphite compositiomillite composition, or 1 :2:3 to 1 :4:8 polysaccharide compositiomgraphite compositiomillite composition, or 1 :2:3 to 1 :3:5 polysaccharide compositiomgraphite compositiomillite composition. In other words, the graphite composition, illite composition and polysaccharide composition may be present in a weight ratio of 3:3:1 to 5:10:1 of graphite composition:illite composition:polysaccharide composition, for example, 3:4:1 to 4:10:1 graphite compositiomillite composition:polysaccharide composition, 1.5:2:1 to 5:10:1 graphite compositiomillite compositiompolysaccharide composition, 2.5:4:1 to 4:10:1 graphite compositiomillite compositiompolysaccharide composition, 3:4:1 to 4:9:1 graphite compositiomillite compositiompolysaccharide composition, 2:2:1 to 4:9:1 graphite compositiomillite compositiompolysaccharide composition, 1.5:2:1 to 4:8:1 graphite compositiomillite compositiompolysaccharide composition, or 2:3:1 to 4:8:1 graphite compositiomillite compositiompolysaccharide composition, or 2:3:1 to 3:5:1 graphite compositiomillite composition: polysaccharide composition.

[0064]

[0046] The molding sand additive package may be a dry composition. The molding sand additive package may not be in the form of an aqueous suspension. The molding sand additive package may be essentially free of water. As used herein, “essentially free of water” may mean less than 15.0wt.%, less than 12.5wt.%, less than 10.0wt.%, less than 7.5wt.%, less than 5.0 wt.%, less than 2.5 wt.%, less than 1 .0 wt.%, less than 0.5 wt.%, or less than 0.1 wt.%, less than 0.05 wt.%, less than 0.01 wt.% water, based on the total weight of the molding sand additive package.

[0065]

[0047] In accordance with a second aspect, there is provided a molding sand binder composition comprising a binding agent and the additive package according to the first aspect.

[0066]

[0048] The binding agent may be or may comprise inorganic material. The binding agent may be or may comprise a clay or clay containing material. The binding agent may be or may comprise a clay or clay containing material such as smectite; montmorillonite; hectorite; saponite; nontronite, beidellite; sauconite; ball clay; fire clay; laponite; bentonite; kaolinite; chlorite or a combination thereof. The binding agent may be or may comprise bentonite. The binding agent may be or may comprise sodium bentonite, calcium bentonite, potassium bentonite, or aluminium bentonite. For example, bentonite may have a median particle size, d5o, of from about 10 pm to about 60 pm, or from about 15 pm to about 55 pm, or from about 20 pm to about 50 pm, or from about 25 pm to about 45 pm, or from about 30 pm to about 40 pm. For example, bentonite may have a median particle size, d5o, of 10 pm, of about 12 m, or about 14 pm, or about 16 pm, or about 18 pm, or about 22 pm, or about 25,9 pm, or about 28 pm.

[0067]

[0049] The binding agent may be present in the molding sand binder composition in an amount from 45 wt.% to about 95 wt.%, based on the total weight of the molding sand binder composition. For example, the binding agent may be present in an amount of from about 50 wt.% to about 90 wt.%, or from about 55 wt.% to about 85 wt.%, or from about 60 wt.% to about 80 wt.%, or from about 65 wt.% to about 75 wt.%, based on the total weight of the molding sand binder composition.

[0068]

[0050] The graphite composition may be present in the molding sand binder composition in an amount of from about 1 wt.% to about 25 wt.%, based on the total weight of the molding sand binder composition. For example, the graphite composition may be present in an amount from about 2.5 wt.% to about 20 wt.%, or from about 5 wt.% to about 15 wt.%, or from about 7.5 wt.% to about 12.5 wt.%, or from about 5 wt.% to about 15 wt.%, based on the total weight of the molding sand binder composition.

[0069]

[0051] The illite composition may be present in the molding sand binder composition in an amount of about 2 wt.% to about 40 wt.%, based on the total weight of the molding sand binder composition. For example, the illite composition may be present in an amount from about 2.5 wt.% to about 35 wt.%, or from 5 wt.% to about 30 wt.%, or about 7.5 wt.% to about 25 wt.%, or from about 10 wt.% to about 20 wt.%, or from about 12.5 wt.% to about 17.5 wt.%, or from about 5 wt.% to about 20 wt.%, based on the total weight of the molding sand binder composition.

[0070]

[0052] The polysaccharide composition may be present in the molding sand binder composition in an amount of from about 0.25 wt.% to about 10 wt.%, based on the total weight of the molding sand binder composition. For example, the polysaccharide composition may be present in an amount of from about 0.5 wt.% to about 8 wt.%, or from about 1 wt.% to about 6 wt.%, or from about 2.5 wt.% to about 4 wt.%, based on the total weight of the molding sand binder composition.

[0071]

[0053] The graphite composition may be present in the molding sand binder composition in an amount of from about 1 to 25 wt.%, the illite composition may be present in the molding sand binder composition in an amount of from about 2 wt.% to about 40 wt.%, the polysaccharide composition may be present in the binder composition in an amount of from about 0.25 wt.% to about 10 wt.%, and the remainder of the binder composition may be bentonite, wherein all wt.% are based on the total weight of the molding sand binder composition. The graphite composition may be present in the molding sand binder composition in an amount of from about 1 wt.% to about 25 wt.%, the illite composition may be present in the molding sand binder composition in an amount of from about 2 wt.% to about 40 wt.%, the polysaccharide composition may be present in the binder composition in an amount of from about 0.25 wt.% to about 10 wt.%, and bentonite may be present in an amount of about 35 wt.% to about 93.75 wt.%, wherein all wt.% are based on the total weight of the molding sand binder composition.

[0072]

[0054] The graphite composition may be present in the molding sand binder composition in an amount of from about 5 to 15 wt.%, the illite composition may be present in the molding sand binder composition in an amount of from about 10 wt.% to about 20 wt.%, the polysaccharide composition may be present in the binder composition in an amount of from about 1 wt.% to about 10 wt.%, and the remainder of the binder composition may be bentonite, wherein all wt.% are based on the total weight of the molding sand binder composition. The graphite composition may be present in the molding sand binder composition in an amount of from about 5 wt.% to about 15 wt.%, the illite composition may be present in the molding sand bindercomposition in an amount of from about 10 wt.% to about 20 wt.%, the polysaccharide composition may be present in the binder composition in an amount of from about 1 wt.% to about 10 wt.%, and bentonite may be present in an amount of about 55 wt.% to about 84 wt.%, wherein all wt.% are based on the total weight of the molding sand binder composition.

[0073]

[0055] The graphite composition may be present in the molding sand binder composition in an amount of from about 7.5 wt.% to about 12.5 wt.%, the illite composition may be present in the molding sand binder composition in an amount of from about 12.5 wt.% to about 17.5 wt.%, the polysaccharide composition may be present in the molding sand binder com position in an amount of from about 2.5 wt.% to about 5 wt.%, and the remainder of the binder composition may be bentonite, wherein all wt.% are based on the total weight of the molding sand binder composition.

[0074]

[0056] The binder composition may be free or essentially free of fossil fuel species or species derived from fossil fuels. The binder composition may be free or essentially free of coal. As used herein, “essentially free of coal” may mean less than 2 wt.%, less than 1 .5 wt.%, less than 1 .0 wt.%, less than 0.5 wt.%, less than 0.3 wt.%, less than 0.2 wt.%, less than 0.1 wt.%, less than 0.05 wt.%, or less than 0.01 wt.% coal, based on the total weight of the binder composition. The binder composition may be free or essentially free of petroleum resin e.g., hydrocarbon resin. As used herein, “essentially free of petroleum resin e.g., hydrocarbon resin” may mean less than 0.5 wt.%, less than 0.3 wt.%, less than 0.2 wt.%, less than 0.1 wt.%, less than 0.05 wt.%, or less than 0.01 wt.% petroleum resin e.g., hydrocarbon resin, based on the total weight of the binder composition. The binder composition may be free or essentially free of coal and petroleum resin e.g., hydrocarbon resin. The binder com position may comprise reduced levels of fossil fuel species or species derived from fossil fuels. The binder composition may comprise reduced levels of coal. For example, the binder composition may comprise less than 45 wt.%, less than 40 wt.%, less than 35 wt.%, less than 30 wt.%, less than 25 wt.%, less than 20 wt.%, less than 15 wt.%, less than 10 wt.%, less than 5.0 wt.%, or less than 2.5 wt.% coal, based on the total weight of the binder composition. The binder composition may comprise reduced levels of petroleum resin e.g., hydrocarbon resin. For example, the binder composition may comprise less than 5 wt.%, less than 4.5 wt.%, less than 4 wt.%, less than 3.5 wt.%, less than 3 wt.%, less than 2.5 wt.%, less than 2 wt.%, less than 1.5 wt.%, less than 1 wt.% petroleum resin e.g., hydrocarbon resin, based on the total weight of the binder composition.

[0075]

[0057] The binder composition may be a dry composition. The binder composition may not be in the form of an aqueous suspension. The binder composition may be essentially free of water. As used herein, “essentially free of water” may mean less than 15.0 wt.%, less than 12.5 wt.%, less than 10.0 wt.%, less than 7.5 wt.%, less than 5.0 wt.%, less than 2.5 wt.%, less than 1 .0wt.%, less than 0.5 wt.%, or less than 0.1 wt.%, less than 0.05 wt.%, less than 0.01 wt.% water, based on the total weight of the binder composition. The binder composition may not comprise dispersing aids, such as surfactants. The binder composition may be free of dispersing aids, such as surfactants.

[0076]

[0058] In accordance with a third aspect, there is provided a molding sand comprising an aggregate and the molding sand binder composition according the second aspect.

[0059] The aggregate may be a natural material or a synthetic material. The aggregate may be a sand material. The aggregate may be a silicate or aluminosilicate material. The aggregate may be selected from silica sand, zirconia sand, chromite sand, quartz sand, non-silica synthetic sand, aluminosilicates or combinations thereof. The aggregate may be a silica sand. The silica sand may be natural silica sand and / or synthetic silica sand. The aggregate may have a median particle size, d5o, of from about 200 pm to about 350 pm, or from about 220 pm to about 320 pm, or from about 240 pm to about 300 pm, or from about 260 pm to about 280 pm.

[0077]

[0060] The aggregate may be present in the molding sand in an amount of from about 50 wt.% or more, based on the total weight of the molding sand. For example, the aggregate may be present in an amount from about 60 wt.% or more, or from about 70 wt.% or more, or from about 80 wt.% or more, or from about 90 wt.% or more, based on the total weight of the molding sand. The aggregate may be present in the molding sand in an amount of from about 75 wt.% to about 99 wt.%, for example, from about 80 wt.% to about 98 wt.%, or from about 85 wt.% to about 95 wt.%, based on the total weight of the molding sand.

[0078]

[0061] The molding sand binder composition may be present in the molding sand in an amount of from about 50 wt.% or less, based on the total weight of the molding sand. For example, the molding sand binder composition may be present in an amount of about 40 wt.% or less, or about 30 wt.% or less, or about 20 wt.% or less, or about 10 wt.% or less, based on the total weight of the molding sand. The molding sand binder composition may be present in the molding sand in an amount of from about 0.5 wt.% to about 30 wt.%, for example, from about 1 wt.% to about 25 wt.%, or from about 2.5 wt.% to about 20 wt.%, or from about 5 wt.% to about 15 wt.%, based on the total weight of the molding sand.

[0079]

[0062] The molding sand may not comprise dispersing aids, such as surfactants. The molding sand may be free of dispersing agents, such as surfactants.

[0080]

[0063] In accordance with a fourth aspect, there is provided a use of a molding sand according to the third aspect to form a casting mold.

[0081]

[0064] In accordance with a fifth aspect, there is provided a use of a molding sand additive package according the first aspect, to reduce casting defects in molding sand.

[0082]

[0065] In accordance with a sixth aspect, there is provided a method comprising: blending the molding sand additive package according to the first aspect with a binding agent, to provide a molding sand binder; blending the molding sand binder with an aggregate to provide a molding sand; mixing the molding sand with water; and preparing a mold by forming the molding sand and water mixture into a shape. In some examples, the molding sand is mixed with between from about 1 .8 wt.% to about 3.8 wt.% of water, based on the total weight of the molding sand. For example, water is present in an amount of from about 2.0 wt.% to about 3.6 wt.%, or from about 2.2 wt.% to about 3.4 wt.%, or from about 2.4 wt.% to about 3.2 wt.%, or from about 2.6 wt.% to about 3.0 wt.%, or from about 2.8 wt.% to about 2.9 wt.%, or from about 2.1 wt.% to about 2.7 wt.%, or from about 2.8 wt.% to about 3.6 wt.%, based on the total weight of the molding sand.

[0083]

[0066] The method of sand casting may further comprise: introducing a metal or metal alloy into the mold to form a casted article; and removing the casted article from the mold. The metal or metal alloy may be molten. The molding sand may be recycled in further casting processes. The molding sand may be reusable.

[0084]

[0067] The present disclosure may be described by one or more of the following paragraphs:

[0085] A. A molding sand additive package comprising a graphite composition, an illite composition and a polysaccharide composition.

[0086] B. The molding sand additive package according to paragraph A, wherein the illite composition comprises or is a deagglomerated illite composition.

[0087] C. The molding sand additive package according to paragraphs A or B, wherein the illite composition has a median particle size, d5o, of about 100 pm or less.

[0088] D. The molding sand additive package according to any preceding paragraph, wherein the illite composition comprises at least about 50 wt.% illite, based on the total weight of the illite composition.

[0089] E. The molding sand additive package according to any preceding paragraph, wherein the graphite composition comprises or is a macrocrystalline graphite.

[0090] F. The molding sand additive package according to any preceding paragraph, wherein the polysaccharide composition comprises or is starch. G. The molding sand additive package according to paragraph F, wherein the starch is pre-gelatinised starch.

[0091] H. The molding sand additive package according to any preceding paragraph, wherein the additive package is essentially free of coal.

[0092] I. The molding sand additive package according to any preceding paragraph, wherein the graphite composition, illite composition and polysaccharide composition are present in a weight ratio of 3:3:1 to 5:10:1 of graphite composition:illite composition: polysaccharide composition.

[0093] J. A molding sand binder composition comprising the molding sand additive package according to any preceding paragraph and a binding agent.

[0094] K. The molding sand binder composition according to paragraph J wherein the binding agent comprises or is a clay or clay containing material.

[0095] L. The molding sand binder composition according to paragraph K, wherein the clay or clay containing material is selected from smectite; montmorillonite; hectorite; saponite; nontronite, beidellite; sauconite; ball clay; fire clay; laponite; bentonite; kaolinite; chlorite or a combination thereof.

[0096] M. The molding sand binder composition according to anyone of paragraphs J to L, wherein the binding agent comprises or is bentonite.

[0097] N. The molding sand binder composition according to anyone of paragraphs J to M, wherein the graphite composition is present in an amount of about 1 wt.% to about 25 wt.%, based on the total weight of the molding sand binder composition.

[0098] O. The molding sand binder composition according to anyone of paragraphs J to N, wherein the illite composition is present in an amount of about 2 wt.% to about 40 wt.%, based on the total weight of the molding sand binder composition.

[0099] P. The molding sand binder composition according to anyone of paragraphs J to O, wherein the polysaccharide composition is present in an amount of about 0.25 wt.% to about 10 wt.%, based on the total weight of the molding sand binder composition. Q. The molding sand binder composition according to anyone of paragraphs J to P, wherein the graphite composition is present in an amount of from about 1 wt.% to about 25 wt.%, the illite composition is present in an amount of from about 2 wt.% to about 40 wt.%, the polysaccharide composition is present in an amount of from about 0.25 wt.% to about 10 wt.%, wherein all wt.% are based on the total weight of the molding sand binder composition.

[0100] R. The molding sand binder composition according to paragraph Q, wherein the binder is present in an amount of about 35 wt.% to about 93.75 wt.%, based on the total weight of the molding sand binder composition.

[0101] S. The molding sand binder composition according to paragraph R, wherein the binder is bentonite.

[0102] T. A molding sand comprising an aggregate and the molding sand binder composition according to any one of paragraphs J to S.

[0103] U. The molding sand according to paragraph T, wherein the aggregate is selected from silica sand, zirconia sand, chromite sand, quartz sand, non-silica synthetic sand, aluminosilicates or combinations thereof.

[0104] V. The molding sand according to paragraph V, wherein the silica sand is natural silica sand and / or synthetic silica sand.

[0105] W. Use of a molding sand according to anyone of paragraphs T to V to form a casting mold.

[0106] X. Use of a molding sand additive package according to any one of paragraphs A to I, to reduce casting defects in molding sand.

[0107] Y. A method of sand casting, the method comprising: blending the molding sand additive package of any one of paragraphs A to I with a binding agent, to provide a molding sand binder composition; blendingthe moldingsand bindercomposition with an aggregate to provide a molding sand; mixing the molding sand with water; and preparing a mold by forming the molding sand and water mixture into a shape.

[0108] Z. The method of paragraph Y, further comprising: introducing a metal or metal alloy into the mold to form a casted article; and removing the casted article from the mold.

[0109] AA. The method of according to paragraph Z, wherein the metal or metal alloy is molten.

[0110] BB. The method of according to any one of paragraphs Y to AA, wherein the molding sand can be recycled in further casting processes.

[0111] EXAMPLES

[0112]

[0068] It is desirable for additives in a molding sand additive package to have low moisture content, high strength, high compaction and / or low permeability. In some cases, good casting quality for molding sand is assured with a molding sand additive package that has low moisture content, high strength, high compaction and low permeability. It is also desirable, from an environmental perspective, for additives in a molding sand additive package to have low emissions, in particular carbonaceous emissions such as CO, CO2, light hydrocarbons and / or BTEX (benzene, toluene, ethylbenzene, xylene) compounds. In order to obtain these low emission, combinations of additives (i.e., molding sand additive packages) may be required.

[0113] Mechanical properties

[0114]

[0069] In order to test the mechanical properties of selected additives and additive packages, additives were blended with bentonite to provide molding sand binder compositions comprising 30 wt.% additive(s) and 70 wt.% bentonite. The molding sand binder compositions were mixed with silica sand and water to provide molding sands comprising 10 wt.% binder composition and 90 wt.% silica sand.

[0115]

[0070] The illite composition used in the examples was Argolitec Gl / F, obtained from Adolf Gottfried Tonwerke GmbH. Argolitec Gl / F contains around 70% illite, around 10% Kaolinte, 12% Calcite and trace amounts of quartz and feldspar.

[0116]

[0071] The graphite composition used in the examples was Graphite GP 80 / 85. Graphite of this specification was obtained from Technografit GmbH or Hargreaves GmbH. This graphite is a macrocystalline graphite.

[0117]

[0072] The polysaccharide composition used in the examples is starch, which was obtained from Ceresan Erfurt GmbH. This starch is a pre-gelatinised starch.

[0118]

[0073] The coal used in the examples was IKO-N obtained from Calderys. This coal is a production milled bituminous coal.

[0119]

[0074] The bentonite used in the example, as a binding agent, was IKO BOND D obtained from Calderys. The bentonite comprises sodium smectite, with minor amounts of calcite, potassium feldspar, dolomite, and quartz, and trace amounts of apatite and anatase.

[0120]

[0075] The silica sand used in the examples, as an aggregate, was obtained from Quarzwerke GmbH. The silica sand is F32.

[0121] Moisture content

[0122] The moisture content of the molding sand samples were measured with a moisture analyzer with high-quality infrared quartz glass heater (DAB 100-3IR KERN). A mass of 5 g (± 0.05 g) was weighed as an initial sample weight, transferred to the moisture analyzer and dried. Moisture content is given in % as a result of mass loss during drying based on initial sample weight.

[0123] Strength (GCS and WTS)

[0076] The green compression strength (GCS) and wet tensile strength (WTS) of the molding sand samples were measured in accordance with Verein Deutscher Giessereifachleute (VDG)- Merkblatt P 38.

[0124]

[0077] For the strength tests, a molding sand sample was placed in a 50 mm diameter cylindricaltesttube. The test sample was compacted to provide a cylindricaltest specimen of 50 mm in diameter and 50 mm in height.

[0125]

[0078] For green compressive strength, the test specimen was loaded into the compressive strength tester (SJ1 , Jung Instruments) with its end faces between a stationary and movable compression disc and compressed. The green compressive strength is the value obtained (in N / cm2), when the test specimen breaks.

[0126]

[0079] For wet tensile strength, the test specimen was loaded into the wet tensile strength tester (PNZ, Georg Fischer Ltd) and one face was heated by a heat plate, which has been brought to a temperature of 310 ± 10°C before the test. As the heat plate is removed, the value obtained (in N / cm2) when the surface of the test specimen fractures across its diameter, is the wet tensile strength.

[0127]

[0080] The strength tests were undertaken in triplicate and the mean value calculated.

[0128] Compaction

[0129]

[0081] For the compaction test, a molding sand sample was placed in a 50mm diameter cylindrical test tube. The test sample was compacted (using an RJ1 , Jung Instruments), three times with an aim of providing a test specimen of 50 mm in diameter and 50 mm in height. If the 50 mm length was not reached, further sample was added and compacted until the 50 mm length is reached. The sample weight of the test specimen is measured. Higher sample weight indicates higher compaction of the sample.

[0130] Permeability

[0131]

[0082] The permeability of the molding sand samples were measured in accordance with Verein Deutscher Giessereifachleute (VDG)- Merkblatt P 41 .

[0083] For the permeability test, a molding sand sample was placed in a 50mm diameter cylindrical test tube. The test sample was compacted to provide a cylindrical test specimen of 50 mm in diameter and 50 mm in height. The cylindrical test tube with the test specimen is placed onto the gas permeability tester (PDU, Georg Fischer Ltd) and the gas permeability read.

[0132]

[0084] The test was carried out in triplicate for each sample.

[0133]

[0085] While permeability is mostly affected by the grain size distribution of the silica sand, the additive packages and binder will also have an effect on the permeability of the molding sand composition.

[0134] Table 1

[0135] ‘Comparative

[0136] 1Binder composition comprises 100% bentonite

[0137] 2Green compressive strength

[0138] 3Wet tensile strength

[0139]

[0086] Without being bound by theory, it is considered that higher moisture adsorption of additives can lead to increased explosion penetration, as a result of increasing gas pressure in the mold arising from the evaporation of water contained in the molding sand during pouring and can result in metal being forced into the molding sand composition. Further it is noted that higher moisture content can decrease the flowability of the molding sand, which can result in poorer mold quality (e.g., unfilled cavities).

[0140]

[0087] It can be seen that in comparison to Example 1 and Example 2, Example 4 had the lowest moisture content of the additives tested, with moisture contents only 0.5 % and 0.3% higher, respectively, than that of Example 1 and Example 2. Example 5 provided the largest increase in moisture content, in comparison to the additive-free composition (Example 1), with a moisture content 1.2% higher. Example 3 was also found to increase the moisture demand of the sand composition, with a moisture content 0.8 % higher than that of Example 1 . The two additive component compositions comprising starch (Examples 7 and 8) are also seen to provide the highest moisture content of the two-component compositions tested while Example 6 provided a moisture content increase similar to that of illite and graphite alone (Examples 3 and 4). The three-component illite:graphite:starch composition (Example 9) provided a slight increase in moisture content than Example 1 and Example 2, but was the next lowest moisture increase after Example 4. Samples comprising additives according to the present invention may have a slightly higher moisture content compared with Example 1 (additive free) and Example 2 (coal). This can in many cases be expected as the moisture content is considered to be connected with the higher surface area associated with the additives used. However, the moisture content of the samples according to present invention was sufficiently low to avoid the negative effects that may be associated with a high moisture content.

[0141]

[0088] One way of improving the surface finishing of castings in order to prevent casting defects, is to increase compaction of the mold, thus reducing its porosity. Example 4 provides the highest sample weight, in comparison to Example 1 and Example 2, indicating increased compaction, which is indicative of decreased porosity and better surface finishing. The compositions containing illite and starch on their own (Examples 3 and 5) do not show any significant change in weight from Example 1 or Example 2. For the two additive component compositions, the compositions comprising graphite (Examples 6 and 8) provided higher sample weights than Example 1 and Example 2, while Example 7 did not showany significant change in weight in comparison to Example 1 or Example 2. The three- component composition of Example 9 provided an increased sample weight in comparison to Example 1 and Example 2.

[0142]

[0089] In combination with higher compaction, lower permeability of the sand mixture is sought, in order to prevent molten metal entering the mold, causing casting defects or an increase in the roughness of the casting surface. Example 4 has a permeability lower than Example 1 and similar to Example 2. Example 3 provides the highest permeability of all the compositions tested. Example 5 has a permeability greater than the Example 2 and similar to Example 1. Example 8 provided the lowest permeability of the two-component compositions, but all two-component compositions had permeabilities lower than Example 1. The three-component composition of Example 9 provided slightly increased permeability over Example 2 but lower permeability than Example 1 .

[0143]

[0090] Additives should not reduce the strength of the molding sand. In particular, additives should not negatively effect in a significant way the green compression strength or wet tensile strength of the molding sand. Example 4 and Example 3 provide higher GCS and WTS than Examples 1 and 2 while Example 5 provided the poorest GCS and WTS of the tested compositions. It was found that Example 6 provided high GCS and the highest WTS of the compositions tested. The two-component compositions containing starch (Examples 7 and 8) had lower GCS and WTS than Example 1 and lower GCS than Example 2, but similar WTS to Example 2. The three-component composition of Example 9 was found to provide increased GCS and WTS over Examples 1 and 2, despite the presence of starch, which caused a decrease in strength (GCS and / or WTS) in all other compositions comprising it, when compared to Examples 1 and 2.

[0144] Emissions analysis

[0145]

[0091] An important consideration for additives used in binding compositions for molding sand, is their environmental impact, in particular, given their use at high temperatures, their potentially hazardous emissions during use must be considered and mitigated where possible.

[0146]

[0092] The additives, additive package and binder samples were dried and then placed on a quartz glass crucible and inserted in a glass rode tube furnace (Carbolite HST 12 / 600) in a nitrogen atmosphere at a temperature of 900°C. The samples are maintained in the glass rod tube furnace until all gases are released, to a maximum time of 7 minutes. The gases released are transported to FT-IR equipment (FT-IR Gasmet Analyzer), via heated tubes, for emissions measurements in real time. The results are then calculated in mg / g of sample (db; dry basis).

[0147]

[0093] Table 2 provides an overview of the volatiles, carbon content and emissions released from the tested additives. The values for Examples 10 to 13 and 15 to 17 were calculated and based on the maximum addition envisaged for each additive to a binding composition. The values for Example 14 were measured. Example 14 is 100% coal additive. Example 15 is a binding composition comprising 30% coal additive and 70% bentonite. Example 16 is an additive package comprising a Graphite, Starch and Illite composition according to the invention. Example 17 is a binding composition comprising graphite, starch, illite compositions and bentonite according to the present invention.

[0148] Table 2

[0149] Comparative

[0150] 1As measured with Eltra CS 500 at 1350°C

[0151] 2Example 15 and Example 17 is additive + bentonite

[0094] Comparing Examples 10 to 13, Example 10 provides the highest % volatiles and % carbon, as well as the highest CO, CH4(methane), C2H4(ethene), C2H2(ethyne) and BTEX (benzene, toluene, ethylbenzene, xylene) of these tested additives for a limited addition, (see %). Example 11 provides low % volatiles and % carbon and no CO, CH4, C2H4, C2H2or BTEX emissions. Example 11 does however, provide the highest CO2emissions of the test additives. This CO2is believed to be a product of calcite decomposition in the illite additive composition. Example 12 provides the lowest % volatiles of the tested additive compositions, and like the illite composition contributes no CO, CH4, C2H4, C2H2or BTEX emissions. Example 12 does provide the second highest % carbon after coal of the tested compositions, but a small amount of CO2emissions. Example 13 has the second highest volatiles % after coal, but at a significantly lower amount (6.2% lower), though it is noted that the maximum concentration envisaged in the binder composition for starch is far lower than that of coal. The highest contributor to emissions from the Example 13 is CO emissions, with CO2, CH4, C2H4, C2H2and BTEX emissions remaining relatively low.

[0152]

[0095] Looking to Examples 14 and 16, which represent the ratio of additive in an additive package intended for a binder composition, Example 14, comprising 100% coal has higher % volatiles and far higher % carbon (around 51% higher). Example 14 also has slightly higher CO emissions and far higher CH4(methane), C2H4(ethene), C2H2(ethyne) and BTEX (benzene, toluene, ethylbenzene, xylene) emissions than Example 16.

[0153]

[0096] Examples 15 and 17 show the emissions for the additive packages of Examples 14 and 16, in a binding composition i.e., the additive packages with bentonite binding agent. As before, the binder composition comprising coal has higher % volatiles and far higher % carbon than binder comprising the present invention.

[0154] Thermal Analysis

[0155]

[0097] The thermal decompositions of the additive species were also tested by Thermogravimetry DifferentialThermalAnalysis (TG-DTA). TheTG-DTAwas measured using a Netzsch STA 409 C / 3 / F over a temperature range of 30°C to1100°C, at a rate of 10K / min, in air.

[0156] Table 3

[0157] Comparative

[0158]

[0098] Table 3 gives the residual mass after thermal decomposition of the tested additives and the temperature range across which decomposition reactions occurred. It is seen that the Examples 19 and 20, have minimal mass loss over the tested temperature range, reflected by their high residual mass at the end of the analysis, indicating high thermal and chemical stability of these species in air. Alternatively, Examples 18 and 20 undergo significant mass loss across the tested temperature range with final residual masses of 0.6% and 5 %, respectively. Further, the decomposition reactions for examples 18 and 20 occur across largely the same temperature range. Without wishing to be bound by theory, it is believed that the chemical and thermal reactivity of examples 18 and 20 aids stress relief in a molding sand at the quartz expansion temperature. It is believed that this reduces the likelihood of expansion defects.

[0159] Casting quality

[0160]

[0099] The molding sand samples were prepared as above mentioned and water added (see Table 4). The sand was then used for Iron casting (1 :2 lron:Sand). After pouring, the molds and casts were allowed to cool for 2 hours before separation. On separation, the larger portions of sand stuck to the surface of the casting surface were removed by hammer by stripping and then by hitting the castthree times to remove the loose sand. The cast was then shotblasted. Sand adhesion

[0161]

[0100] Sand adhesion was measure as the difference in sand sticking to the casting surface before and after shotblasting.

[0162] Surface Roughness

[0163]

[0101] Device: Mitutoyo Surftest SJ-400; Tactile surface measurement; 4 measurements per casting and cycle, result is an average of all cycles (in total 20 measurements).

[0164] Loss on Ignition

[0165]

[0102] The loss on ignition of the molding sand samples were measured in accordance with Verein Deutscher Giessereifachleute (VDG)- Merkblatt P 31 . A 10g aliquot of dried sample is annealed in an oxidising atmosphere at 900°C to a constant weight (over a minimum time of 3 hours). The loss on ignition is measured as the difference in sample weight before and after the annealing process.

[0166] Table 4

[0167] *Comparative1Surface roughness

[0168] Example 23 provided lower % loss on ignition in sand than Example 22. The three- component composition of Example 23 resulted in slightly higher adhering sand amounts than the coal-containing sand composition of Example 22. However, the composition still achieved lowadhering sand amounts while comprising no additional lustrous carbon formers, such as coal or petroleum residue e.g., hydrocarbon residue. It is considered in the art that lustrous carbon formation at the interface of the molding sand and molding medium (e.g. metal) during the casting process improves the casting quality of the molding sand. Therefore, it is considered in the art that lustrous carbon formers (LCF) such as coal or petroleum residue e.g., hydrocarbon residue are necessary in order to achieve good casting quality. However, Example 23, which comprises no additional LCF, achieved lower surface roughness than Example 22. Lower surface roughness is indicative of improved casting quality.

Claims

CLAIMS1. A molding sand additive package comprising a graphite composition, an illite composition and a polysaccharide composition.

2. The molding sand additive package according to claim 1 . wherein the illite composition comprises or is a deagglomerated illite composition and / or wherein the illite composition has a median particle size, d5o, of about 100 pm or less.

3. The molding sand additive package according to any preceding claim, wherein the graphite composition comprises or is a macrocrystalline graphite and / or wherein the polysaccharide composition comprises or is starch, optionally wherein the starch is pre-gelatinised starch.

4. The molding sand additive package according to any preceding claim, wherein the additive package is essentially free of coal.

5. The molding sand additive package according to any preceding claim, wherein the graphite composition, illite composition and polysaccharide composition are present in a weight ratio of 3:3:1 to 5:10:1 of graphite compositiomillite composition: polysaccharide composition.

6. A molding sand binder composition comprising the molding sand additive package of any preceding claim and a binding agent.

7. The molding sand binder composition according to claim 6 wherein the binding agent comprises or is a clay or clay containing material, wherein the clay or clay containing material is selected from smectite; montmorillonite; hectorite; saponite; nontronite, beidellite; sauconite; ball clay; fire clay; laponite; bentonite; kaolinite; chlorite or a combination thereof.

8. The molding sand binder composition according to any one of claims 6 or 7, wherein the graphite composition is present in an amount of about 1 wt.% to about 25 wt.%, based on the total weight of the molding sand binder composition.

9. The molding sand binder composition according to any one of claims 6 to 8, wherein the illite composition is present in an amount of about 2 wt.% to about 40 wt.%, based on the total weight of the molding sand binder composition.

10. The molding sand binder composition according to any one of claims 6 to 9, wherein the polysaccharide composition is present in an amount of about 0.25 wt.% to about 10 wt.%, based on the total weight of the molding sand binder composition.11 . The molding sand binder composition according to any one of claims 6 to 10, wherein the graphite composition is present in an amount of from about 1 wt.% to about 25 wt.%, the illite composition is present in an amount of from about 2 wt.% to about 40 wt.%, the polysaccharide composition is present in an amount of from about 0.25 wt.% to about 10 wt.%, wherein all wt.% are based on the total weight of the molding sand binder composition.

12. A molding sand comprising an aggregate and the molding sand binder composition according to any one of claims 6 to 11 , optionally wherein the aggregate is selectedfrom silica sand, zirconia sand, chromite sand, quartz sand, non-silica synthetic sand, aluminosilicates or combinations thereof.

13. Use of a molding sand according to claim 12 to form a casting mold.

14. Use of a molding sand additive package according to any one of claims 1 to 5, to reduce casting defects in molding sand.

15. A method of sand casting, the method comprising: blending the molding sand additive package of any one of claims 1 to 5 with a binding agent, to provide a molding sand binder composition; blending the molding sand binder composition with an aggregate to provide a molding sand; mixing the molding sand with water; and preparing a mold by forming the molding sand and water mixture into a shape.

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