WO2021209424A1

WO2021209424A1 - Use of a solvent for producing sizes, a process for producing a size, a size and use thereof

Info

Publication number: WO2021209424A1
Application number: PCT/EP2021/059509
Authority: WO
Inventors: Theodorus Johannes KOOIJERS; Hartmut POLZIN; Tom KOOIJERS
Original assignee: Peak Deutschland Gmbh
Priority date: 2020-04-15
Filing date: 2021-04-13
Publication date: 2021-10-21
Also published as: EP4135919A1; DE102020110290A1; DE102020110290A8

Abstract

The invention relates to the use of a solvent consisting of an aqueous, colloidal suspension for producing sizes, to a process for producing a size, to a size and to the use thereof.

Description

Use of a solvent for the production of sizes, a method for the production of a size, a size and the use thereof

The invention relates to the use of a solvent consisting of an aqueous, colloidal suspension for the production of sizes, a method for producing a size, a size and the use thereof.

In the foundry, surface coatings, so-called layers, are often applied to cores or molds in liquid to paste form (suspension), less often in powder form, in order to achieve an improved surface quality of the cast parts, in particular to increase the thermal resistance of the surface of the molding material and to reduce the surface roughness , a reduction in wettability and responsiveness to avoid metal infiltration and sintering reactions, triggering an inoculation effect to influence the crystallization process or influencing the heat extraction rate to influence the solidification process.

Sizes are suspensions whose solid component ensures the separating or smoothing effect of the mold coating. Highly dispersed, refractory materials such as oxides of aluminum, silicon, magnesium and chromium as well as silicates of aluminum, zirconium and magnesium are used. This also includes graphite or coke powder as additives to reduce the reactivity. Metallurgically effective components such as tellurium, bismuth, chromium or silicon can be included as additional components. Essential requirements for the base materials are a high sintering temperature, a low tendency to react with the cast material and little or no formation of harmful substances. Carrier liquids can be water or alcohol (e.g. iso-propanol), whereby the solvent water is more promising due to its better workplace and environmental compatibility. They form a suspension with the base material, the consistency of which is determined by the ratio of solid content to carrier liquid (dispersion medium) (degree of suspension). The degree of suspension has a direct influence on the workability or on the layer thickness achieved with the applied application technology. The setting of an optimal consistency, characterized by the viscosity or density of the suspension, is necessary in order to achieve an adequate protective effect or to avoid the risk of cracks and peeling phenomena.

DE 10 2009 032 668 A1 describes a size for producing mold coatings on lost molds or cores for iron or steel casting, containing a weight-related proportion in the range from 0.001% to 1% of inorganic hollow bodies, preferably Hollow spheres consisting at least partially of crystalline material, preferably silicates, oxides, carbides, nitrides or mixtures thereof.

DE 102017 107655 A1 discloses the use of a sizing composition comprising at least one refractory material and an aqueous phase with a pH value of at most 5 for producing a coating on a water-glass-bonded mold or a core for use in foundries. The water-glass-bound form or the water-glass-bound core preferably contains particulate, amorphous silicon dioxide. The aqueous phase also preferably comprises at least one acid.

Furthermore, DE 10 2017 107 657 A1 describes a sizing composition comprising water and organic ester compounds, particulate silicon dioxide and at least one refractory material for producing a coating on a mold or a core, preferably a water-glass-bound form or a water-glass-bound core, for use in the foundry , especially for use in iron or steel casting.

WO 2009/007 093 A2 discloses a sizing system for protecting casting tools comprising ceramic materials and at least one binder selected from the group consisting of binders based on water glass and refractory binders in combination with fluoride-containing constituents.

When using water-based coatings on inorganically bound molds and / or cores, it is currently not possible to implement this without additional measures such as an external drying unit. The water in the size attacks the inorganic binder, which can result in considerable loss of strength, with the result that the manufactured cores and molds are no longer suitable for casting.

The object of the present invention is therefore to provide a size or a solvent for use in a size which is environmentally friendly and does not attack binders in foundry molds and / or cores.

According to the invention, the object is achieved by the use according to the invention of a solvent consisting of an aqueous, colloidal suspension containing silica sol with a content in the range from 3% by mass to 70% by mass for the production of sizes for foundry cores and / or molds, silica sol being polysilicic acid with a silicon dioxide content in the range of 30% by mass to 60% by mass. The use of the solvent according to the invention comprising silica sol in sizes advantageously results in a reduction in the water content, which means that no drying (water-based size) or burning off (alcohol-based size) is necessary after the size has been applied to foundry molds and / or cores. The solvent according to the invention, comprising silica sol for sizes, is also advantageously environmentally friendly, in particular in comparison to the use of organic solvents. The solvent according to the invention, comprising silica sol, also advantageously does not attack binders in foundry molds and / or cores; it preferably protects inorganic binders in foundry molds and / or cores, since the silica sol can react with the chemically similar SiCk-based binders and increases the strength.

The term “solvent” is understood to mean an inorganic or organic liquid that can physically dissolve other solid or liquid substances. The prerequisite for suitability as a solvent is that neither the solvent nor the dissolved substance change chemically during the dissolving process.

The term “colloidal” is understood to mean the presence, in particular the homogeneous distribution, of particles in a solid, liquid or gaseous dispersion medium, preferably liquid dispersion medium (colloidal suspension), the particles having dimensions in the range from 1 nm to 1 μm.

The term “silica sol” is understood to mean an aqueous, colloidal suspension of polysilicic acid molecules. Silica sol has a sodium and potassium oxide content of at most 1% by mass, preferably a sodium oxide content of at most 1% by mass. In embodiments, silica sol comprises particles in the range from 5 nm to 75 nm. Silica sol is advantageously long-term stable, in particular over several years. The low sodium oxide content advantageously improves drying, particularly in the investment casting process.

In embodiments, the silica sol comprises polysilicic acid with a silicon dioxide content in the range from 30% by mass to 60% by mass, preferably in the range from 30% by mass to 40% by mass. The term “polysilicic acid” is understood to mean polycondensed oxygen acids of silicon which have polar (Si-OH) groups on the surface. In embodiments, the silica sol comprises alkali oxide, preferably sodium oxide. The silica sol is advantageously stabilized by a small amount of alkali oxide. In further embodiments, the ratio of silica sol to alkali oxide is 100: 1.

According to the invention, the solvent contains water.

According to the invention, a solvent containing silica sol is used with a content in the range from 3% by mass to 70% by mass, preferably in the range from 5% by mass to 70% by mass, particularly preferably in the range from 30% by mass to 70% by mass -%, based on the total mass of the solvent.

According to the invention, the constituents of the solvent add up to 100% by mass.

In embodiments, a solvent consisting of silica sol is used to produce coatings for foundry cores and / or molds.

In further embodiments, a solvent is used consisting of an aqueous, colloidal suspension which also contains metal oxide and / or metal silicate nanoparticles.

The term “nanoparticles” is understood to mean particles in any shape, which have dimensions in the range from 1 to 150 nm. Nanoparticles in the size advantageously contribute to a reduced surface roughness or a refinement of the foundry cores and / or molds.

In embodiments, the nanoparticles are round.

In further embodiments, the aqueous, colloidal suspension has metal oxide and / or metal silicate nanoparticles with a content in the range from 10% by mass to 35% by mass based on the total mass of the solvent. The aqueous, colloidal suspension preferably has metal oxide and / or metal silicate nanoparticles with a content in the range from 15% by mass to 31% by mass, based on the total mass of the solvent.

In embodiments, the metal oxide and / or metal silicate nanoparticles have dimensions in the range from 4 nm to 150 nm. In further embodiments, the metal oxide and / or metal silicate nanoparticles consist of silicon dioxide, aluminum silicate, calcium silicate, iron oxide, potassium aluminum silicate, potassium magnesium silicate, iron aluminum silicate, iron germanates, titanates or mixtures thereof.

In embodiments, a solvent is used consisting of an aqueous, colloidal suspension which also contains aluminum phosphate.

In embodiments, the solids content of the solvent is in the range from 10% by mass to 70% by mass, preferably 15% by mass to 65% by mass, based on the mass of water and solids.

The invention also relates to a method for producing a size

Providing a solvent consisting of an aqueous, colloidal suspension containing silica sol with a content in the range from 3% by mass to 70% by mass, silica sol comprising polysilicic acid with a silicon dioxide content in the range from 30% by mass to 60% by mass, and

Mixing the solvent with at least one refractory component, preferably selected from aluminum oxide, zirconium silicate, silicon dioxide, mullite, olivine and magnesite.

In embodiments, the solvent is provided by contacting a silica sol with metal oxide and / or metal silicate nanoparticles in a mass ratio in the range from 1.2: 1 to 35: 1.

In embodiments, the solvent is mixed with at least one refractory component in a mass ratio in the range from 1: 1 to 2: 1.

Another aspect of the invention relates to a size comprising i. a solvent consisting of an aqueous, colloidal suspension containing silica sol with a content in the range from 3% by mass to 70% by mass, silica sol comprising polysilicic acid with a silicon dioxide content in the range from 30% by mass to 60% by mass, and ii. at least one refractory component, preferably selected from aluminum oxide, zirconium silicate, silicon dioxide, mullite, olivine and magnesite. In embodiments, the size comprises solvents with a content in the range from 50% by mass to 99% by mass, preferably in the range from 50% by mass to 70% by mass; and / or the refractory component with a content in the range from 1% by mass to 50% by mass, preferably in the range from 30% by mass to 50% by mass; based on the total mass of the size.

According to the invention, the constituents of the size add up to 100% by mass.

In embodiments, the size further comprises metal oxide and / or metal silicate nanoparticles.

In embodiments of the size, the aqueous, colloidal suspension comprises metal oxide and / or metal silicate nanoparticles with a content in the range from 10% by mass to 35% by mass; preferably in the range from 15% by mass to 31% by mass; based on the total mass of the aqueous, colloidal suspension.

In embodiments of the size, the metal oxide and / or metal silicate nanoparticles have dimensions in the range from 4 nm to 150 nm.

In embodiments of the size, the metal oxide and / or metal silicate nanoparticles are selected from silicon dioxide, aluminum silicate, calcium silicate, iron oxide, potassium aluminum silicate, potassium magnesium silicate, iron aluminum silicate, iron germanates, titanates and mixtures thereof.

In embodiments of the size, the aqueous, colloidal suspension further comprises aluminum phosphate.

In embodiments of the size, the at least one refractory component has an average grain size in the range from 0.05 mm to 0.15 mm. The term “mean grain size” is understood to mean the size or diameter of individual particles, also called grains, of the refractory molded material.

In embodiments of the size, the solids content of the size is in the range from 50% by mass to 90% by mass, preferably 65% by mass to 80% by mass, based on the mass of water and solids. In embodiments, the size has a viscosity at 20 ° C. in the range from 1 to 20 Pa s, preferably in the range from 1 Pa s to 12 Pa s, and / or a surface tension at 20 ° C. in the range from 1 mN / m to 70 mN / m, preferably in the range from 10 mN / m to 35 mN / m.

The size advantageously has a viscosity which necessitates good flow properties and complete wetting when used for surface coating of cured molds, molded parts or cores.

The term “viscosity” is understood to mean the dynamic viscosity. The viscosity is determined using commercially available measuring devices such as falling body or rotation viscometers.

The surface tension is determined, for example, by means of a measuring method using the capillary effect or the contact angle measurement.

In embodiments, the size comprises at least one further component, the component being selected from a defoamer, a suspension agent, a wetting agent, a pigment and / or a dye.

The person skilled in the art knows that the processing properties of the size, such as viscosity and flow behavior, can be adjusted by means of the at least one further component selected from a defoamer, a suspension agent, a wetting agent, a pigment and / or a dye.

The term “defoamer” is understood to mean a substance which is surface-active and reduces foam formation. In embodiments, defoamers are silicone or mineral oils.

The term “suspension means” is understood to mean a settling delay means.

The term “wetting agent” is understood to mean a substance which increases the wetting of foundry cores and / or molds. In embodiments, wetting agents are dioctyl sulfosuccinates, alkynediols, or ethoxylated alkynediols. The size according to the invention usually contains dyes with a content in the range from 0 to 5% by mass, defoamers with a content in the range from 0 to 1% by mass, suspending agents with a content in the range from 0 to 1% by mass and / or Contain wetting agents with a content in the range from 0 to 1% by mass, based on the total mass of the size.

Another aspect of the invention relates to the use of the solvent according to the invention and / or the size according to the invention for surface coating of cured organically or inorganically bound molds, moldings or cores, preferably of inorganically bound molds, moldings or cores.

When used for surface coating, it is expediently applied by dipping, flooding, spraying or brushing onto the cured organically or inorganically bound molds, moldings or cores. The person skilled in the art is aware that, depending on the method for producing the surface coating, the size must have suitable processing properties, in particular with regard to viscosity.

In embodiments, it is used for surface coating of foundry cores and / or molds, preferably for metal casting, particularly preferably for iron, steel, copper or aluminum casting.

The inventive solvent comprising silica sol advantageously has a similar composition to inorganic binders for foundry molds and / or cores, whereby the surface of the coated foundry molds and / or cores has a reduced surface roughness or refinement and increased strength.

To implement the invention, it is also expedient to combine the embodiments and features of the claims described above.

The invention is to be explained in more detail below with the aid of some exemplary embodiments and associated figures. The exemplary embodiments are intended to describe the invention without restricting it.

1 shows a diagram of the use of a size for the surface coating of foundry cores and / or molds, in particular the grains of the basic mold material and the size layer thickness in the range from 0.1 to 2.0 mm. Solvent

In a first exemplary embodiment, the solvent contains 37.5% by mass of silica sol, 10% by mass of ALCh nanoparticles, 20% by mass of magnesium silicate nanoparticles, 1% by mass of FeO nanoparticles, 0.01% by mass of defoamer and 31, 49 Mass% water.

In a second exemplary embodiment, the solvent contains 50% by mass of silica sol, 20% by mass of aluminum phosphate with an average grain size of about 0.1 mm, 17% by mass of iron-magnesium-silicate nanoparticles and 13% by mass of water.

plain

In a first embodiment, the size contains 60% by mass of the solvent according to the first embodiment and 40% by mass of chamotte with an average grain size in the range from 0.05 mm to 0.15 mm.

In a second embodiment, the size contains 65% by mass of the solvent according to the second embodiment and 35% by mass of zirconium silicate with an average grain size in the range from 0.05 mm to 0.15 mm.

Claims

1. Use of a solvent consisting of an aqueous, colloidal suspension containing silica sol with a content in the range from 3% by mass to 70% by mass for the production of sizes for foundry cores and / or molds, silica sol being polysilicic acid with a silicon dioxide content in the range of 30% by mass to 60% by mass.

2. Use of a solvent according to claim 1, characterized in that the aqueous, colloidal suspension further contains metal oxide and / or metal silicate nanoparticles, the metal oxide and / or metal silicate nanoparticles having dimensions in the range from 4 nm to 150 nm.

3. Use of a solvent according to claim 2, characterized in that the

Metal oxide and / or metal silicate nanoparticles are selected from silicon dioxide, aluminum silicate, calcium silicate, iron oxide, potassium aluminum silicate,

Potassium magnesium silicate, iron aluminum silicate, iron germanates, titanates and their mixtures.

4. Use of a solvent according to one of claims 1 to 3, characterized in that the solids content of the solvent is in the range from 10% by mass to 70% by mass based on the mass of water and solids.

5. A method for producing a size comprising

6. Sizing comprising i. a solvent consisting of an aqueous, colloidal suspension containing silica sol with a content in the range from 3% by mass to 70% by mass, wherein Silica sol comprises polysilicic acid with a silicon dioxide content in the range from 30% by mass to 60% by mass and ii. at least one refractory component, preferably selected from aluminum oxide, zirconium silicate, silicon dioxide, mullite, olivine and magnesite.

7. Sizing according to claim 6, further comprising metal oxide and / or metal silicate nanoparticles, the metal oxide and / or metal silicate nanoparticles having dimensions in the range from 4 nm to 150 nm.

8. Size according to claim 7, characterized in that the metal oxide and / or metal silicate nanoparticles are selected from silicon dioxide, aluminum silicate, calcium silicate, iron oxide, potassium aluminum silicate, potassium magnesium silicate, iron aluminum silicate, iron germanates, titanates and mixtures thereof.

9. Size according to one of claims 6 to 8, characterized in that the solids content of the size is in the range from 50% by mass to 90% by mass based on the mass of water and solids.

10. Size according to one of claims 6 to 9, characterized in that the size comprises at least one further component, the component being selected from a defoamer, a suspension agent, a wetting agent, a pigment and / or a dye.

11. Use of a solvent according to one of claims 1 to 4 and / or a size according to one of claims 6 to 10 for the surface coating of cured organically or inorganically bound molds, moldings or cores.

12. Use according to claim 11 for the surface coating of foundry cores and / or molds, preferably for metal casting, particularly preferably for iron, steel, copper or aluminum casting.