Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/10—Cores; Manufacture or installation of cores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/18—Finishing

Definitions

• the invention relates to a size, which is particularly suitable for large-scale casting, a method for producing a casting and a mold with a mold coating.
• the lost forms usually consist of a mineral, refractory, granular molding material, often with different added to other additives, for example to achieve good casting surfaces, which is solidified with the aid of a binder.
• a refractory granular molding material usually washed, classified quartz sand is used.
• quartz sand is used.
• chromite, zirconium and olivine sand are also used.
• moldings based on chamotte, magnesite, silimanite or corundum are also used.
• the binders with which the molding materials are solidified may be inorganic or organic in nature.
• Permanent molds are used to make a variety of castings. You must therefore survive undamaged the casting process and the associated loads. Depending on the field of application, cast iron, unalloyed and alloyed steels, as well as copper, aluminum, graphite, sintered metals and ceramics, have been used as material for permanent molds Proven materials. Permanent molding processes include the mold, pressure, spin and continuous casting processes.
• sizing usually consists of an inorganic refractory and a binder, which are dissolved or slurried in a suitable solvent, for example water or alcohol.
• the surface of the mold can be modified and matched to the properties of the processed Me ⁇ talls.
• the Ausse ⁇ hen of the casting can be obtained by the sizing can be improved by a smooth Oberflä ⁇ surface is generated, as will be offset by the size irregularities ⁇ caused by the size of the grains of the molding material.
• the sizing may metallurgically influence the casting by transmitting selectively on the surface of the casting additives into the Gus ⁇ piece for example through the Schlich ⁇ te, which improve the surface properties of the casting.
• the sizings form a layer which chemically isolates the casting mold from the liquid metal during casting.
• the sizing ensures a thermal separation of mold and casting. This is particularly important in permanent forms of importance. If this function is not fulfilled, learns eg a metal form in the course of successive casting operations such high ther ⁇ mix stresses that it is destroyed prematurely.
• the sizing can also be used to selectively control the heat transfer between the liquid metal and the casting mold in order, for example, to effect the formation of a specific metal structure by the cooling rate.
• the commonly used sizings contain as basic materials such as clays, quartz, diatomaceous earth, cristobalite, tridymite, aluminum silicate, zirconium silicate, mica, chamotte or coke or graphite. These base materials cover the surface of the mold and close the pores against penetration of the liquid metal into the mold. Because of their high insulating power sizing is often used, which contain Siliziumdi ⁇ oxide or kieselguhr as raw materials, since these sizings can be produced at low cost and are available in large quantities.
• the paste still contains a binder, usually water glass.
• a binder usually water glass.
• These pastes are applied to surfaces of the casting mold , which come into contact with the liquid metallic material, usually steel, during casting.
• the metals contained in the paste should be protected by the heat of the melt liquid metallic material and form an alloy with this locally on the surface of the casting, which then solidifies as a peripheral shell.
• edge shells with a thickness of up to 10 mm can be produced. These edge shells can then have a very high hardness. In order to produce a mold, such as an excavator bucket, it would be with this method therefore no longer erforder ⁇ Lich produce the entire casting from the corresponding alloy.
• the invention therefore an object of the invention to propose measures by which an improvement in the surface of the casting can be achieved during metal casting, so that the extent of surface treatment of the casting can be reduced after the casting.
• the metallic ⁇ Addi tive contained in the sizing composition according to the invention contains at least a metal or a metal Ver ⁇ bond, wherein the metal is selected from one of groups 7 or 9 to 12 of the Periodic Table of Elements.
• the numbering of the groups refers to the current regulations of the IUPAC. According to the old rules of IUPAC, group 7 corresponds to group VIIA.
• Groups 9 and 10 correspond to the elements Co, Rh, Ir and Ni, Pd and Pt of the old group VIIIA and groups 11 and 12 correspond to the groups IB and IIB, respectively, of the old notation.
• the metallic additive may contain a metal, ie the metal in the oxidation state zero, wherein the metal can be used both in pure form or in the form of an alloy with other metals.
• the metallic additive can also be present in the form of an oxidized metal, ie in the form of an oxide or a salt, such as a carbonate, a nitrate or chloride, the oxide being preferred.
• the metal in a reduced form, ie in the oxidation state zero.
• the metallic additive can be contained in the metallic additive more of the metals or compounds of these metals mentioned. However, preferably only one of the metals, in reduced or oxidized form, is contained in the metallic additive.
• metals and their compounds are used in the metallic additive, which are selected from the groups 7, 10 or 11 of the Periodic Table of the Elements, with manganese, nickel and copper being particularly preferred.
• the metal additive may be formed only from the mentioned metal ⁇ len or compounds thereof. However, it is also possible that, in addition to these metals or their compounds, further metals or compounds are contained in the metallic additive.
• the metal or the metallic compound calculated as metal and based on the weight of the metallic additive, in a proportion of at least 10 wt .-%, preferably in an amount of at least 20 wt .-%, preferably in one Content of at least 30 wt .-%, more preferably in a proportion of at least 40 wt .-%, particularly preferably in a proportion of at least 50 wt .-% in the metallic additive.
• the metallic additive is formed only by at least one of said metals, in particular manganese, nickel, copper. However, according to one embodiment, it is sufficient if the metal or its compound in a proportion of less than 90 wt .-%, according to another embodiment in an amount of less than 80 wt .-%, according to yet another embodiment in a Content of less than 70% by weight is contained in the metallic additive.
• the sizing composition may contain, in addition to the metallic additive, further customary for sizing ingredients.
• the metallic additive based on the solids content of the sizing composition, in a proportion of at least 10 wt .-%, preferably at least 15 wt .-%, especially preferably at least 20% by weight is contained in the sizing composition.
• the surface or edge shell should have essentially the same composition as sections of the casting which are spaced from the surface of the casting, ie in its volume are. It is therefore preferably provided that the proportion of the metallic additive in the sizing composition, based on the solids content of the sizing composition, is less than 50% by weight, preferably less than 40% by weight, particularly preferably less than 35% by weight ,
• the metallic additive can only contain at least one of the abovementioned metals, preferably at least one of the metals manganese, nickel and copper.
• the at least one metal in the form of an alloy is contained in the metallic additive.
• the metal is contained in the form of an iron alloy in the metallic additive.
• the proportion of iron in the metallic additive, calculated as elemental iron, is preferably selected in the range from 20 to 80% by weight, preferably from 30 to 70% by weight.
• the alloy may also contain other ingredients.
• the metallic aluminum as an additive ingredient wherein the proportion of Alumini ⁇ around the metallic additive, calculated as elemental Alumini ⁇ to, preferably is less than 10 wt .-%, preferably less than 8 wt .-% selected.
• the metallic additive contains aluminum in a proportion of more than 2 wt .-%.
• metallic additive comprises a proportion of aluminum in the range of 2 to 8 wt .-%, preferably 3 to 6 wt .-%, preferably 3 to ⁇ particular to 5 wt .-%.
• the metallic additive can also be used in the form of a silicon alloy according to one embodiment.
• the proportion of silicon in such a silicon alloy is preferably in Range selected from 20 to 80 wt .-%, particularly preferably 50 to 70 wt .-%.
• the metallic additive may also comprise further constituents, in particular metals, the proportion of which is preferably less than 2% by weight, preferably less than 1% by weight.
• These further constituents are preferably selected from the group of cerium, magnesium, chromium, molybdenum.
• the proportions of these alloy constituents are preferably between 0.01 and 2 wt .-%, preferably 0.1 to 1 wt .-% based on the metallic additive.
• the metallic additive may also contain calcium.
• the content of calcium is preferably selected in the range of 0.2 to 2 wt .-%, particularly preferably 0.5 to 1.5 wt .-%.
• the grain size of the metallic additive should preferably not be too low, in particular if the metals, preferably manganese, nickel and copper are contained in elemental form in the metallic additive, since then there is an increased risk that the metallic additive with other components of the The sizing composition reacts and is oxidized, for example.
• the grain size should preferably not be too large, since otherwise the metallic additive can sink, for example, in the sizing composition and thus an inhomogeneous application of the metallic additive takes place on the surface of a casting mold.
• the metallic additive preferably has an average particle size (D 50 ) of less than 0.5 mm, preferably less than 0.4 mm, particularly preferably less than 0.3 mm.
• the average particle size (D 50 ) can be determined, for example, by sieve analysis or by laser granulometry.
• the metallic additive contained in the size according to the invention usually has a relatively high density and therefore decreases rapidly in the size. Although this decrease can be slowed down by adding an actuating agent. However, by decreasing the grain size, the decrease of the seeding agent can be further reduced so that the seeding agent remains homogeneously suspended in the sizing. As a further advantage, when using a spray device for applying the size, the nozzle of the spray device clogs less easily when using a metallic fine grain additive.
• the inoculant has an average grain size of less than 0.3 mm.
• the specific surface area of the metallic additive increases and thus also the reactivity with the liquid contained in the size, for example water.
• the mean grain size is greater than 50 microns, more preferably selected greater than 80 microns.
• the metallic additive is used with a grain size in the range of 20 to 1000 microns, more preferably from 80 to 300 microns.
• the sizing composition according to the invention is preferably provided in the form of a paste or a suspension.
• the sizing composition contains a carrier liquid.
• This carrier liquid is suitably selected from ⁇ so that it can be completely evaporated at the usual conditions in metal casting.
• the carrier liquid should therefore preferably at normal pressure have a boiling point of less than about 130 0 C, preferably less than 110 0 C.
• the carrier liquid can be proportionately or completely formed by water.
• the metallic additive but in the form of elemental metals or an alloy elementary Metals present, however, occasionally an oxidation of the metallic additive is observed.
• the sizing composition therefore, a solvent which is formed at least to a proportion of an organic ⁇ rule solvent.
• the oxidation of the metallic additive is suppressed by a high proportion of the organic solvent, for example an alcohol, on the carrier liquid.
• the organic solvent for example an alcohol
• the carrier liquid may be completely formed by the organic solvent.
• the proportion of the organic solvent in the carrier liquid can also be chosen to be smaller.
• the proportion of the organic solvent in the liquid carrier is less than 90 wt .-%, according to a further exporting ⁇ approximate shape less than 80 wt .-%, and in another embodiment less than 70 wt .-%.
• Suitable solvents include, for example, aliphatic, cycloaliphatic or aromatic hydrocarbons preferably comprising 5 to 15 carbons, esters of aliphatic carboxylic acids wherein the carboxylic acids preferably contain 2 to 20 carbon atoms and the alcohol component of the ester preferably comprises 1 to 4 carbon atoms.
• Further preferred organic solvents are, for example, ketones having preferably 4 to 20 carbon atoms.
• ethers are suitable as solvents, it also being possible to use polyglycols here.
• the solvent is at least partly formed by at least one alcohol, which preferably comprises 1 to 10 carbon atoms.
• Exemplary alcohols are ethanol, n-propanol, isopropanol and butanol.
• the ratio, based on the weight of the carrier liquid is preferably greater than 50 wt .-%, preferably greater than 60 wt .-% selected.
• the size composition according to the invention may contain further constituents customary for sizes.
• the sizing composition according to the invention comprises at least one pulverulent refractory material.
• This refractory material serves to close the pores in a mold against the penetration of the liquid metal. Further, a specific thermi ⁇ insulation between the mold and liquid metal is achieved by the refractory material.
• refractory material conventional refractory materials can be used in metal casting.
• Suitable refractory materials are quartz, aluminum oxide, zirconium oxide, aluminum silicates, such as pyropyllite, kyanite, andalusite or chamotte, zirconium sands, ciconsilicates, olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolins, calcined kaolins, kaolinite , Metakaolinite, iron oxide, bauxite.
• quartz aluminum oxide
• zirconium oxide aluminum silicates
• aluminum silicates such as pyropyllite, kyanite, andalusite or chamotte
• zirconium sands such as pyropyllite, kyanite, andalusite or chamotte
• zirconium sands such as pyropyllite, kyanite, andalusite or chamotte
• zirconium sands such as pyropy
• the refractory material is provided in powder form.
• the grain ⁇ size is chosen so that in the coating a stable ⁇ les structure is formed and that the size can be preferably spread easily with a spray device on the wall of the mold.
• the refractory material has an average particle size in the range from 0.1 to 500 ⁇ m, particularly preferably in the range from 1 to 200 ⁇ m.
• particular special materials are suitable which have a melting point which is at least 200 ° C above the temperature of the liquid metal and which do not undergo reaction with the metal.
• the proportion of the refractory material, based on the solids content of the sizing composition is preferably greater than 10 wt .-%, preferably greater than 20 wt .-%, particularly preferably RESIZE ⁇ SSER than 30 wt .-% selected.
• the fraction of the refractory material is chosen to be less than 80% by weight, according to a further embodiment less than 70% by weight and according to a further embodiment less than 60% by weight.
• the size according to the invention may comprise at least one setting agent.
• the adjusting agent causes an increase in the viscosity of the size, so that the solid components of the size in the suspension do not fall or only to a small extent.
• organic and inorganic materials or mixtures of these materials can be used.
• Suitable inorganic adjusting agents are, for example, strong swellable clays.
• the viscosity of the size is preferably in particular before ⁇ selected before ⁇ in the range of 1,000 to 3,000 mPas, Trains t from 1200 to 2000 mPas.
• the metal additive can then approximately homogeneously distributed in the size and will therefore be uniformly applied to a wall ei ⁇ ner mold.
• the amount of metallic additive which is applied to the surface of the casting mold can be controlled very precisely.
• both two-layer silicates and three-layer silicates can be used, such as eg attapulgite, serpentine, kaolins, smectites, such as saponite, montmorillonite, beidellite and nontronite, vermiculite, illite, hectorite and mica.
• Hectorite also imparts thixotropic properties to the sizing, thereby facilitating the formation of the protective layer on the casting mold since the sizing does not flow after application.
• the amount of clay is preferably chosen to be as low as possible.
• the amount of the highly swellable layered silicate is preferably selected in the range of 0.01 to 5.0 wt%, more preferably in the range of 0.1 to 1.0 wt%, based on the solid content of the size.
• organic thickeners are selected as adjusting agents, since they can be dried to such an extent after application of the protective coating that they hardly give off any more water on contact with the liquid metal.
• Suitable organic agents are, for example, swellable polymers, such as carboxymethyl, methyl, ethyl, hydroxyethyl and hydroxypropyl cellulose, plant mucilage, polyvinyl alcohols, polyvinylpyrrolidone, pectin, gelatin, agar agar and polypeptides, alginates.
• the fiction, modern ⁇ sizing comprises as a further constituent at least one binder.
• the binder allows a better fixation of the size or of the protective coating produced from the size on the wall of the mold.
• the mechanical stability of the protective coating is increased, so that a lower erosion under the influence of flüssi ⁇ gen metal is observed by the binder.
• the binder cures irreversibly, so that an abrasion-resistant coating is obtained.
• binders which are in contact do not back up with humidity. All binders which are used in sizing can be contained per se. In this case, both inorganic and organic binders can be used.
• Clays for example clays, in particular bentonite, can be used as binders.
• curable binders are used.
• curing can be achieved by free-radical formers which decompose upon irradiation with high energy radiation, for example, ultraviolet radiation to form free radicals.
• exemplary binders are starch, dextrin, peptides, polyvinyl alcohol, polyvinyl acetate copolymers, polyacrylic acid, polystyrene and / or polyvinyl acetate-polyacrylate dispersions.
• binder systems which can be used in aqueous, alcoholic or aqueous-alcoholic systems and which do not soften after curing under the action of atmospheric moisture.
• the binder used is an alkyd resin, which is preferably selected to be soluble in both water and lower alcohols, preferably having from 2 to 4 carbon atoms, such as ethanol, n-propanol and isopropanol.
• the coating composition according to the invention contains silica sol as binder.
• the silica sol is preferably prepared by neutralizing water glass.
• the resulting amorphous silica preferably has a specific surface area in the range from 10 to 1000 m 2 / g, particularly preferably in the range from 30 to 300 m 2 / g.
• the proportion of the binder is preferably selected in the range of 0.1 to 20 wt .-%, particularly preferably 0.5 to 5 wt .-%, based on the solids weight of the sizing composition.
• the size contains a proportion of graphite.
• the proportion of graphite is preferably selected in the range of 1 to 30 wt .-%, particularly preferably 5 to 15 wt .-%, based on the weight of the size.
• the size composition according to the invention may also contain further components customary for sizing, for example wetting agents, defoamers, pigments, dyes or biocides.
• the proportion of these further constituents in the ready-to-use coating composition is preferably chosen to be less than 1% by weight.
• wetting agents such as anionic and non-anionic surfactants medium- and high polarity can be used to ⁇ which have a value of at least HSB. 7
• a case ⁇ play for such a wetting agent is disodium succinate dioctylsulfo-.
• the wetting agent is preferably used in an amount of 0.01 to 1 wt .-%, preferably 0.05 to 0.3 wt .-%, based on the ready-to-use sizing composition.
• Defoamers or antifoam agents may be used to prevent foaming in the preparation of the sizing composition or in applying it. Foaming on application of the sizing composition can result in uneven layer thickness and holes in the coating.
• silicone or Mi ⁇ neralöl can be used.
• the defoamer is in an amount of 0.01 to 1 wt .-%, preferably from 0.05 to 0.3 Wt .-%, based on the ready-to-use sizing composition.
• any commonly used pigments and dyes may be used. These are added in order to achieve a different contrast, for example between different layers, or to bring about a greater separation effect of the size of the casting.
• pigments are red and yellow iron ⁇ oxide and graphite.
• dyes are commercially available dyes such as the Luconyl ® color range of BASF AG, Ludwigshafen, Germany.
• the dyes and pigments are preferably contained in an amount of 0.01 to 10 wt .-%, preferably from 0.1 to 5 wt .-%, based on the solids content of the sizing composition.
• the sizing composition contains a biocide to prevent bacterial attack, thereby avoiding a negative impact on the rheology and binding power of the binding agents.
• a biocide to prevent bacterial attack, thereby avoiding a negative impact on the rheology and binding power of the binding agents.
• the carrier liquid contained in the sizing composition is formed essentially of water, so the sizing composition according to the invention is provided in the form of a so-called water wash.
• suitable biocides are formaldehyde, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-iosthiazolin-3-one (CIT) and 1,2-benzisothiazolin-3-one (BIT).
• MIT, BIT or a mixture thereof are used.
• the biocides are usually used in an amount of from 10 to 1000 ppm, preferably from 50 to 500 ppm, based on the weight of the ready-to-use sizing composition.
• the solids content of the ready Schlichtezusammenset ⁇ wetting is preferably selected in the range of 10 to 60 wt .-%, preferably 20 to 50 wt .-%.
• the sizing composition according to the invention can be prepared by conventional methods.
• a sizing composition according to the present invention can be prepared by initially charging water and breaking up a clay acting as a sizing agent using a high shear stirrer. Subsequently, the refractory components, pigments and dyes and the metallic additive are stirred until a homogeneous mixture is formed. Finally, wetting agents, anti-foaming agents, biocides and binders are added.
• the sizing composition according to the invention can be prepared and sold as ready-to-use sizing.
• the size according to the invention can also be prepared and sold in concentrated form.
• the amount of carrier liquid necessary to adjust the desired viscosity and density of the size is added.
• the sizing composition of the invention may be provided in the form of a kit and distributed who ⁇ , wherein, for example, exist together, the solid components and the solvent ⁇ component in separate containers.
• the solid components can be provided as a powdery Feststoffge ⁇ mixed in a separate container.
• An inventive Sizing in the ready-to-use state preferably comprises a solids content of from 20 to 80% by weight, preferably from 30 to 70% by weight, based on the ready-to-use sizing composition.
• the first solvent component is only water.
• a volatile alcohol or alcohol mixture preferably ethanol, propanol, isopropanol and mixtures thereof, in preferably amounts of from 40 to 200% by weight, based on the water size
• a ready-to-use alcohol sizing agent can be prepared from this water sizing.
• the solids content of such an alcohol sizing is preferably from 20 to 60 wt .-%, preferably 30 to 40 wt .-%.
• sizing compositions according to the invention used for coating molds and cores in foundry technology have a viscosity of 11 to 25 s, more preferably 12 to 15 s (determined in accordance with DIN 53211, outlet cup 4 mm, Ford cup).
• Preferred densities of a ready-to-use sizing composition are in the range of 0 to 120 ° Be, more preferably 30 to 50 ° Be (determined by the Baume buoyancy method, DIN 12791).
• the sizing compositions according to the invention are suitable for coating casting molds.
• the term "casting ⁇ form” includes all types of bodies, which are necessary for producing a casting, such as cores, molds and Ko ⁇ kill.
• the use according to the invention of the sizing composition Settlement also includes partial coating of molds.
• a further subject of the invention therefore relates to a method for producing a casting mold, wherein at least one mold cavity provided in the casting mold is coated with the size composition according to the invention.
• a molding material mixture which at least ⁇ contains a refractory mold material and a binder,
• Material mixture for the preparation of form a refractory mold material is mixed with a Bindemit ⁇ tel and then formed into a basic shape or to a portion of a basic form.
• the basic shape essentially corresponds in shape to the casting mold or a part of the casting mold. However, it does not yet have a coating with a size.
• refractory molding material all refractory materials that are customary for the production of moldings for the foundry industry can be used per se.
• suitable refractory mold materials are quartz sand, zircon sand, olivine sand, chromite and Alumi ⁇ niumsilikatsand or mixtures thereof.
• quartz sand is used.
• the refractory molding material should have a have sufficient particle size, so that the molded body produced from the molding mixture has a sufficiently high porosity to allow escape of volatile compounds during the casting process.
• At least 70 wt .-%, particularly preferably at least 80 wt .-% of the refractory molding material has a particle size ⁇ 290 microns.
• the average particle size of the refractory molding material should preferably be between 100 and 350 ⁇ m.
• the particle size can be determined, for example, by sieve analysis.
• the refractory molding material should be in free-flowing form, so that a binder or a liquid catalyst can be applied well, for example in a mixer to the grains of the refractory molding material.
• regenerated used sands may be used as the refractory molding material. From the used sand larger aggregates are removed and the used sand is separated into individual grains. After a mechanical or thermal treatment, the old sands are dedusted and can then be reused. Before being used again the acid balance of the active ⁇ ner convinced used sand is preferred checked. Particularly during thermi ⁇ rule regeneration can be converted into the corresponding oxides by-products contained in the sand such as carbonates, which then react alkaline. If binders used, the un ⁇ ter catalysis be cured by an acid, in this case the added acid catalyst can be neutralized by the alkaline components of the regenerated used sand.
• the processing time of the molding material mixture can be shortened.
• the refractory molding material should be dry.
• the refractory molding material contains less than 1 wt .-% water.
• the refractory molding material should not be too warm.
• the refractory molding material should have a temperature in the range of 20 to 35 ° C. Possibly. the refractory molding material can be cooled or heated.
• binders all binders can be used per se, as are customary for the production of casting molds for metal casting. It can both inorganic and organic ⁇ specific binders.
• inorganic binder for example, water glass can be used, which can be cured thermally or by introducing carbon dioxide.
• organic binders are polyurethane no-bake and cold-box binders, binders based on furan resins or phenolic resins, or else epoxy-acrylate binders.
• Polyurethanes based on polyurethanes are generally composed of two components, a first component containing a phenolic resin and a second component containing a polyisocyanate. These two components are mixed with the refractory molding material and the molding mixture is brought into a mold by ramming, blowing, shooting or other method, compacted and then cured. Depending on the method in which the catalyst is introduced into the molding material mixture, a distinction is made between the "polyurethane no-bake process" and the "polyurethane cold-box process".
• a liquid catalyst generally a liquid tertiary amine
• phenol resin, polyisocyanate and curing catalyst with the refractory mixed molding material proceed in such a way that the refractory molding material is first coated with a component of the binder, and then the other component is added.
• the curing catalyst is added to one of the components.
• the ready-made molding material mixture must have a sufficiently long processing time, so that the molding material mixture can be plastically deformed for a sufficient time and processed into a molding.
• the polymerization must be correspondingly slow so that not already in the storage tanks or supply lines hardening of the molding material mixture.
• the curing should not be too slow to achieve a sufficiently high throughput in the production of molds.
• the processing time can be influenced for example by adding retarders, which slow down the curing of the molding material mixture.
• a suitable retarder is, for example, phosphorus oxychloride.
• the molding material mixture is first brought into a mold without catalyst.
• a gaseous tertiary amine is then passed, wel ⁇ ches may optionally be added with an inert carrier gas.
• wel ⁇ ches may optionally be added with an inert carrier gas.
• the binder binds very quickly, so that a high throughput in the production of molds is achieved.
• the binder systems based on polyurethanes contain a polyol component and a polyisocyanate component, in which case known components can be used.
• the polyisocyanate component of the binder system may comprise an aliphatic, cycloaliphatic or aromatic isocyanate.
• the polyisocyanate preferably contains at least 2 isocyanate groups, preferably 2 to 5 isocyanate groups per mole of lekül.
• the isocyanates used can consist of mixtures of monomers, oligomers and polymers and are therefore referred to below as polyisocyanates.
• the polyisocyanate component per se can be any polyisocyanate which is customary in polyurethane binders for molding mixtures for the foundry industry.
• Suitable polyisocyanates include aliphatic polyisocyanates, e.g. Hexamethylene diisocyanate, alicyclic polyisocyanates, e.g. 4,4'-dicyclohexylmethane diisocyanate, and dimethyl derivatives thereof.
• aromatic polyisocyanates examples include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate and methyl derivatives thereof, diphenylmethane-4,4'-diisocyanate and polymethylene-polyphenyl polyisocyanate.
• aromatic polyisocyanates more preferably polymethylene polyphenyl polyisocyanate, such as e.g. commercially available mixtures of diphenylmethane-4,4'-diisocyanate, its isomers and higher homologs.
• the polyisocyanates can be used both in substance and dissolved in an inert or reactive solvent.
• a reactive solvent is understood to mean a solvent which has a reactive group, so that it is incorporated into the framework of the binder when the binder is set.
• the polyisocyanates are preferably used in Dilution ⁇ ter shape because of the lower viscosity of the solution to better envelop the grains of the refractory mold material with a thin film of the binder.
• the polyisocyanates or their solutions in organic complementary and ⁇ stuffs are used in sufficient concentration to accomplish the hardening of the polyol component, constructiveerwei ⁇ se in a range of 10 to 500 wt .-% based on the weight of the polyol component.
• Liquid polyisocyanates can be used in undiluted form while solid or viscous polyisocyanates are dissolved in organic solvents.
• Up to 80 wt .-%, preferably up to 60 wt .-%, particularly preferably up to 40 wt .-% of the isocyanate component may consist of solvents.
• the polyisocyanate is used in an amount such that the number of isocyanate groups is 80 to 120%, based on the number of free hydroxyl groups of the polyol component.
• polyol component all polyols used in polyurethane binders can be used per se.
• the polyol component contains at least 2 hydroxyl groups which may react with the groups of the polyisocyanate component Isocyanatgrup ⁇ , to achieve crosslinking of the binder during curing, and thus a better strength of the cured molding.
• phenolic resins are preferably used, obtained by condensation of phenols with aldehydes, preferably Formalde ⁇ hyd, are obtained in the liquid phase at temperatures up to about 180 0 C in the presence of catalytic amounts of metal.
• aldehydes preferably Formalde ⁇ hyd
• the processes for the preparation of such phenolic resins are known per se.
• the polyol is preferably used in liquid or dissolved in organic solvents to obtain a homogeneous distri ⁇ development of the binder in the refractory mold material to ermögli ⁇ chen.
• the polyol component is preferably used in anhydrous form, because the reaction of the isocyanate component with Water is an undesirable side reaction.
• Non-aqueous or anhydrous in this context means a water content of the polyol component of preferably less than 5 wt .-%, preferably less than 2 wt .-%, mean.
• phenolic resin means the reaction product of phenol, phenol ⁇ derivatives, bisphenols and higher phenolic condensation products is meant with an aldehyde.
• the composition of the phenolic resin ⁇ is dependent on the specific selected starting materials, the ratio of the starting materials and the reaction conditions. For example, the type of catalyst, the time and the reaction temperature play an important role, as well as the presence of solvents and other substances.
• the phenolic resin is typically present as a mixture of different compounds and may contain in widely varying ratio ⁇ sen addition products, condensation products, and not the other way releasing ⁇ te starting compounds, such as phenols, bisphenol and / or aldehyde.
• addition product is meant reaction products in which an organic component substituted by at least a hydrogen on a not previously substituted phenol or a Kondensati ⁇ ons.
• condensation product is meant reaction products having two or more phenolic rings.
• Novolacs are soluble, meltable, non-self-curing, and shelf-stable oligomers having a molecular weight in the range of about 500 to 5,000 g / mole. They fall in the condensation of aldehydes and phenols in a molar ratio of 1:> 1 in counter ⁇ wart acidic catalysts. Novolacs are phenol resins free of methylol groups in which the phenyl nuclei are linked via methylene bridges. They may be cured at elevated temperature with crosslinking after addition of curing agents, such as formaldehyde donating agents, preferably hexamethylenetetramine.
• curing agents such as formaldehyde donating agents, preferably hexamethylenetetramine.
• Resoles are mixtures of hydroxymethylphenols which are linked via methylene and methylene ether bridges and can be obtained by reaction of aldehydes and phenols in a molar ratio of 1: ⁇ 1, if appropriate in the presence of a catalyst, for example a basic catalyst. They have a molecular weight M w of ⁇ 10,000 g / mol.
• phenol resins particularly suitable as polyol component are known under the name "oo 1 " or "high-ortho” novolaks or benzyl ether resins. These are obtainable by condensation of Phe ⁇ nolen with aldehydes in a weakly acidic medium using suitable catalysts.
• Suitable catalysts for the preparation of benzylic ether resins are salts of divalent ions of metals such as Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca and Ba. Preferably, zinc acetate is used. The amount used is not critical. Typical amounts of metal catalyst are 0.02 to 0.3 wt .-%, preferably 0.02 to 0.15 wt .-%, based on the total amount of phenol and Alde ⁇ hyd.
• phenolic resins are all suitable conventionally used ⁇ th phenols.
• substituted phenols or mixtures thereof can be used.
• the phenolic compounds are unsubstituted either in both ortho positions or in an ortho and in the para position to allow polymerization.
• the remaining ring carbon atoms may be substituted.
• the choice of Substituent is not particularly limited so long as the substituent does not adversely affect the polymerization of the phenol or aldehyde.
• substituted phenols are alkyl-substituted phenols, alkoxy-substituted phenols and aryloxy-substituted phenols.
• the abovementioned substituents have, for example, 1 to 26, preferably 1 to 15, carbon atoms.
• suitable phenols are o-cresol, m-cresol, p-cresol, 3,5-xylene, 3,4-xylene, 3, 4, 5-trimethylphenol, 3-ethylphenol, 3, 5-diethylphenol, p-butylphenol, 3, 5-dibutylphenol, p-amylphenol, cyclohexylphenol, p-octylphenol, p-nonylphenol, 3, 5-dicyclohexylphenol, p-crotylphenol, p-phenylphenol, 3, 5-dimethoxyphenol and p-phenoxyphenol.
• phenol itself.
• higher condensed phenols such as bisphenol A, are suitable.
• polyhydric phenols having more than one phenolic hydroxyl group are also suitable.
• Preferred polyhydric phenols have 2 to 4 phenolic hydroxyl groups.
• suitable polyhydric phenols are pyrocatechol, resorcinol, hydroquinone, pyrogallol, fluoroglycine, 2,5-dimethylresorcinol, 4,5-dimethylresorcinol, 5-methylresorcinol or 5-ethylresorcinol.
• Mixtures of various mono- and polyhydric and / or substituted and / or condensed phenolic components can also be used for the preparation of the polyol component.
• phenols of general formula I are phenols of general formula I:
• A, B and C independently of one another from a hydrogen atom, a branched or unbranched alkyl radical, which may have, for example 1 to 26, preferably 1 to 15 carbon atoms, a branched or unbranched alkoxy radical, for example 1 to 26, preferably having from 1 to 15 carbon atoms, a branched or unbranched alkenoxy radical which may, for example, have 1 to 26, preferably 1 to 15, carbon atoms, an aryl or alkylaryl radical, such as, for example, bisphenyls.
• a branched or unbranched alkyl radical which may have, for example 1 to 26, preferably 1 to 15 carbon atoms, a branched or unbranched alkoxy radical, for example 1 to 26, preferably having from 1 to 15 carbon atoms, a branched or unbranched alkenoxy radical which may, for example, have 1 to 26, preferably 1 to 15, carbon atoms, an aryl or alkylaryl radical, such as, for example, bispheny
• Suitable aldehydes for the production of the phenolic resin component are aldehydes of the formula:
• R is a hydrogen atom or a carbon atom radical having preferably 1 to 8, particularly preferably 1 to 3 carbon atoms.
• Specific examples are formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and benzaldehyde. Particular preference is given to using formaldehyde, either in its aqueous form, as para-formaldehyde or trioxane.
• molar ratio is preferably Aldehyde to phenol 1: 1.0 to 2.5: 1, more preferred
• the production of the phenolic resin component takes place by methods known to the person skilled in the art.
• the phenol and the aldehyde is reacted under substantially anhydrous conditions in the presence of a divalent metal ion at temperatures of preferably less than 130 0 C.
• the resulting water is distilled off.
• a suitable entraining agent may be added to the reaction mixture, for example toluene or xylene, or the distillation is carried out at reduced pressure.
• an aldehyde preferably Benzyletherharzen.
• the reaction with a primary or secondary aliphatic alcohol to give an alkoxy-modified phenolic resin in the one-stage or two-stage process is likewise possible.
• step process the phenol, the aldehyde and the alcohol in the presence of a geeigne ⁇ th catalyst are reacted.
• an unmodified resin is first prepared, which is subsequently reacted with an alcohol.
• Consists in the use alkoxymod instructer phenolic resins with respect to the mole ratio in itself is not limited, but the Alko ⁇ holkomponente is preferably in a molar ratio of alcohol to phenol of less than 0.25 is used, that less than 25% of the hydroxymethyl groups are etherified.
• Suitable alcohols are primary and secondary aliphatic alcohols having a hydroxy group and 1 to 10 carbon atoms. Suitable primary and secondary alcohols are, for example, methanol, ethanol, propanol, n-butanol and n-hexanol. Particularly preferred are methanol and n-butanol.
• the phenolic resin is preferably selected so that crosslinking with the polyisocyanate component is possible.
• phenolic resins comprising molecules having at least two hydroxyl groups in the molecule are particularly suitable.
• the phenolic resin component and the isocyanate component of the binder system ⁇ medium is preferably used as a solution in an organic solvent or a combination of organic complementary and ⁇ stuffs.
• Solvents may be required to keep the components of the binder in a sufficiently low viscosity state. This is required, inter alia, in order to obtain a uniform crosslinking of the refractory molding material and its flowability.
• solvents for the polyisocyanate or the polyol component of the binder system based on polyurethanes all solvents which are conventionally used in such binder systems for foundry technology can be used per se.
• Suitable solvents are, for example, oxygen-rich, polar, organic solvents.
• Particularly suitable are dicarboxylic acid esters, glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters or cyclic carbonates.
• Dicarboxylic acid esters, cycli ⁇ specific ketones and cyclic carbonates are preferably used.
• Dicarboxylic acid esters have the formula R a OOC-R b -COOR a , wherein the radicals R a are each independently an alkyl group having 1 to 12, preferably 1 to 6 carbon atoms and R b is an alkylene lengue, ie a divalent alkyl group with 1 to 12, be ⁇ preferably 1 to 6 carbon atoms. R b may also include one or more carbon-carbon double bonds. Examples are dimethyl esters of carboxylic acids having 4 to 10 carbon atoms, which are obtainable, for example, under the name "dibasic ester" (DBE) from Invista International S.A.rl, Geneva, CH.
• DBE dibasic ester
• Glycol ether esters are compounds of the formula R c -OR d - OOCR e , where R c is an alkyl group having 1 to 4 carbon atoms, R d is an ethylene group, a propylene group or an oligomeric ethylene oxide or propylene oxide and R e is an alkyl group having 1 to 3 carbon atoms. Preference is given to glycol ether acetates, for example butylglycol acetate. Glycol diesters accordingly have the general formula R e COO-R d OOCR e , where R d and R e are as defined above and the radicals R e are each independently selected.
• glycol diacetates such as propylene glycol diacetate.
• Glycol diethers can be characterized by the formula R c -OR d -OR c , where R c and R d are as defined above and the radicals R c are each independently selected.
• a suitable glycol diether is, for example, dipropylene glycol dimethyl ether.
• Cyclic ketones, cyclic esters and cyclic carbonates of 4 to 5 carbon atoms are also suitable.
• a suitable cyclic carbonate is, for example, propylene carbonate.
• the alkyl and alkylene groups may each be branched or unbranched.
• the proportion of the solvent in the binder system is preferably not chosen too high, since the solvent evaporates during the production and application of the molded article produced from the molding compound and thus, for example, can lead to unpleasant odors or leads to smoke during the casting.
• the proportion of the solvent in the binder system is less than 50 wt .-%, more preferably less than 40 wt .-%, more preferably less than 35 wt .-%, selected.
• the binder is first mixed with the refractory mold material to form a material mixture.
• a suitable catalyst can also already be added to the molding material mixture.
• Suitable catalysts are 4-alkylpyridines, wherein the alkyl group comprises 1 to 4 carbon atoms, isoquinoline, arylpyridines, such as phenylpyridine, pyridine, acrylin, 2-methoxypyridine, pyridazine, 3-chloropyridine, quinoline, n-methylimidazole, 4, 4 ' -Dipyridine, phenylpropylpyridine, 1-methylbenzimidazole, 1,4-thiazine, N, N-dimethylbenzylamine, triethylamine, tribenzylamine, N, N-dimethyl-1,3-propanediamine, N, N-dimethylethanolamine, and triethanolamine.
• arylpyridines such as phenylpyridine, pyridine, acrylin, 2-methoxypyridine, pyridazine, 3-chloropyridine, quinoline, n-methylimidazole, 4, 4 ' -Di
• the catalyst may optionally be diluted with an inert solvent, for example 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, or a fatty acid ester.
• an inert solvent for example 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, or a fatty acid ester.
• the amount of catalyst added is selected in the range of 0.1 to 15% by weight, based on the weight of the polyol component.
• the molding material mixture is then introduced by conventional means into a mold and compacted there.
• the molding material mixture is then cured to a shaped body.
• the shaped body should preferably retain its outer shape.
• a gaseous catalyst is passed through the shaped molding material mixture.
• the usual Ka gas catalytic converters can be used in the field of the cold-box method.
• amines as catalysts, in particular preferably dimethylethylamine, dimethyl-n-propylamine, dimethylisopropylamine, dimethyl-n-butylamine, triethylamine and trimethylamine in their gaseous form or as aerosol.
• a furan resin or a phenolic resin is used as the binder, wherein the molding material mixture is cured according to the "furan no-bake" method with catalysis by a strong acid.
• Furan and phenolic resins show very good disintegration properties during casting. Under the action of heat of the liquid metal, the furan or phenolic resin decomposes and the strength of the mold is lost. After casting, therefore, cores, possibly after prior shaking of the casting, pour out very well from cavities.
• furan no-bake binders contained ⁇ requested reactive furan resins comprise as an essential component furfuryl alcohol.
• Furfuryl alcohol can react with itself under acid catalysis and form a polymer.
• furfurylalko ⁇ hol other compounds are Siert the copolymerized in the resin. Examples of such compounds are Alguerhy ⁇ de, such as formaldehyde or furfural, ketones such as acetone, phenols, urea or polyols, such as sugar alcohols or to ethylene glycol.
• the resins may be added with other components that affect the properties of the resin, such as its elasticity. Melamine may for example be set to ⁇ to bind free formaldehyde.
• Furan no-bake binders are usually displayed in a manner by first furfuryl Dictionary precondensates of example, urea, formaldehyde and furfuryl alcohol are generated at acidic Bedingun ⁇ gen. The reaction conditions are chosen so that only a slight polymerization of furfuryl alcohol occurs. These precondensates are then diluted with furfuryl alcohol ⁇ .
• Resoles can also be used to prepare furan no-bake binders. Resoles are prepared by polymerization of mixtures of phenol and formaldehyde. These resoles are then diluted with furfuryl alcohol.
• the second component of the furan no-bake binder forms an acid.
• This acid neutralises alkaline components
• the crosslinking of the reactive furan resin catalyzes them, which are contained in the refractory molding material.
• acids mostly aromatic sulfonic acids and in some special cases also phosphoric acid or sulfuric acid are used.
• Phosphoric acid is used in concentrated form, ie at concentrations greater than 75%.
• Sulfuric acid can be added as a relatively strong acid starter for the curing of furan resins to weaker acids.
• aromatic sulfonic acids are used as catalysts. Because of their good availability and their high acidity especially toluene sulfonic acid, xylylene sulfonic acid and benzenesulfonic acid are used.
• Phenolic resins as the second large group under acid catalysis aushärtba ⁇ rer no-bake binders contain as reactive resin component resoles, phenolic resins thus produced with an excess of Formalde ⁇ hyd. Phenol resins show a significantly lower reactivity compared to furan resins and require strong sulfonic acids as catalysts. Phenol resins show a rela ⁇ tively high viscosity, which still increases with prolonged storage of the resin. Especially at temperatures below 20 0 C, the viscosity increases sharply, so that the sand must be heated in order to apply the binder evenly on the surface of the grains of sand can.
• the molding compound After the phenol no-bake binder has been applied to the refractory molding material, the molding compound should be processed as promptly as possible in order to prevent any deterioration in the quality of the molding material mixture. having to accept early curing, which can lead to a deterioration in the strength of the molds produced from the molding material mixture.
• the flowability of the molding material mixture is usually poor. In the production of the casting mold, therefore, the molding compound must be carefully compacted in order to achieve a high strength of the casting mold.
• the preparation and processing of the molding material mixture should be carried out at temperatures in the range of 15 to 35 0 C. If the temperature is too low, the molding material mixture is difficult to process because of the high viscosity of the phenol no-bake resin. At temperatures of more than 35 ° C., the processing time is shortened by premature curing of the binder.
• molding mixtures based on phenol no-bake binders can also be worked up again, in which case mechanical or thermal or combined mechanical / thermal processes can also be used.
• An acid is then introduced ⁇ on the free-flowing refractory material, wherein an acid-coated refractory molding material is obtained.
• the acid is applied by conventional methods to the fi ⁇ erfesten molding material, for example by the acid is sprayed onto the refractory mold material.
• the amount of acid is preferably selected in the range of 5 to 45 wt .-%, particularly preferably in the range of 20 to 30 wt .-%, based on the weight of the binder and calculated as the pure acid, ie without taking into account any used solvent.
• the acid is dissolved in a suitable solvent.
• suitable solvents are water or alcohol system ⁇ le or mixtures of water and alcohol.
• the use of water makes the solution as concentrated as possible in order to minimize the amount of water entrained in the binder or the molding material mixture.
• the mixture of refractory molding material and acid is well homogenized.
• An acid-curable binder is then applied to the acid-coated refractory molding material.
• the amount of the binder is preferably selected in the range of 0.25 to 5 wt .-%, particularly preferably in the range of 1 to 3 wt .-%, based on the refractory molding material and calculated as the resin component.
• a curable acid binders are all binders may be used per se, curable by acid, particularly those curable by acid binding ⁇ medium, which are already common in the manufacture of mold mixes for the foundry industry.
• the binder may also contain other customary components, for example solvents for adjusting the viscosity or extenders which replace part of the crosslinkable resin.
• the binder is applied to the acid-coated refractory molding material and distributed by moving the mixture on the grains of the refractory molding material in the form of a thin film.
• the amounts of binder and acid are that ei ⁇ is achieved necard a sufficient strength of the mold and on the other hand, ⁇ a sufficient processing time of the molding material mixture so selected. For example, a processing time in the range of 5 to 45 minutes is suitable.
• the coated with the binder refractory molding material is then formed by conventional methods to a shaped body.
• the molding material mixture can be introduced into a suitable mold and be condensed there.
• the resulting molded body is then allowed to cure.
• furan no-bake binder all furan resins can be used per se, as they are already used in furan no-bake binder systems.
• the furan resins used in technical furan no-bake binders are usually precondensates or mixtures of furfuryl alcohol with other monomers or precondensates.
• the precondensates contained in furan no-bake binders are prepared in a manner known per se.
• furfuryl alcohol is used in combination with urea and / or formaldehyde or urea / formaldehyde precondensates.
• Formaldehyde can be used both in a monomeric form, for example in the form ei ⁇ ner formalin, as well as in the form of its polymer, such as Trio xan or paraformaldehyde.
• formaldehyde other aldehydes or ketones can be used.
• Suitable aldehydes are, for example, acetaldehyde, propionaldehyde, butyraldehyde, acrolein, crotonaldehyde, benzaldehyde, salicylaldehyde, cinnamaldehyde, glyoxal and mixtures of these aldehydes.
• Formaldehyde is preferred, this being preferably used in the form of paraformaldehyde.
• ketones As ketone component, all ketones can be used which have a sufficiently high reactivity.
• Exemplary keto ⁇ ne are methyl ethyl ketone, methyl propyl ketone and acetone, acetone is preferably used.
• the said aldehydes and ketones can be used as a single compound but also in admixture with each other.
• the molar ratio of aldehyde, in particular formaldehyde, or ketone to furfuryl alcohol can be selected within wide ranges.
• 0.4 to 4 moles of furfuryl alcohol, preferably 0.5 to 2 moles of furfuryl alcohol, may be used per mole of aldehyde.
• furfuryl alcohol, formaldehyde and urea can be heated to boiling, for example, after adjusting the pH to more than 4.5, with water being continuously distilled off from the reaction mixture.
• the reaction time can be several hours, crizspielswei ⁇ se 2 hours. Under these reaction conditions occurs almost no polymerization of furfuryl alcohol. However, the furfuryl alcohol is condensed into a resin together with the formaldehyde and the urea.
• furfuryl alcohol, form ⁇ aldehyde and urea are set at a pH significantly below 4.5, for example at a pH of 2.0, in the heat by ⁇ , wherein the water formed in the condensation under can be distilled off reduced pressure.
• the reaction product has a relatively high viscosity and is diluted with furfuryl alcohol to produce the binder until the desired viscosity is achieved.
• phenol can be reacted under alkaline conditions, first with formaldehyde to a resole resin.
• This resol can then be reacted or mixed with furfuryl alcohol or a furan group-containing resin.
• furan phenomenonhalti ⁇ gen resins can be obtained, for example, the methods described above.
• higher phenols for example resorcinol, cresols or else bisphenol A.
• the proportion of phenol or higher phenols in the binder is preferably in the range of up to 45% by weight, preferably up to 20% by weight, in particular ⁇ dess preferably selected up to 10 wt .-%. According to one embodiment, the proportion of phenol or higher phenols can be greater than 2 wt .-%, according to a further embodiment greater than 4 wt .-% can be selected.
• condensates of aldehydes and ketones which are then mixed with furfuryl alcohol to produce the binder.
• Such condensates can be prepared by reacting aldehydes and ketones under alkaline conditions.
• the aldehyde used is preferably formaldehyde, in particular in the form of paraformaldehyde.
• the ketone used is preferably acetone.
• the relative molar ratio of aldehyde to ketone is preferably selected in the range of 7: 1 to 1: 1, preferably 1.2: 1 to 3.0: 1.
• the condensation is preferably carried out under alkaline conditions at pH values in the range of 8 to 11.5, preferably 9 to 11.
• a suitable base is, for example, sodium carbonate.
• the proportion of the Furfurylalko ⁇ hols to the binder ranges from 30 to 95 wt .-%, is preferably 50 to 90 wt .-%, particularly preferably 60 to 85 wt .-% selected.
• the proportion of urea and / or formaldehyde on the binder is preferably in the range of 2 to 70 wt .-%, preferably 5 to 45 wt .-%, particularly preferably 15 to 30 wt .-% selected.
• the Antei ⁇ le include both the unbound portions of these compounds contained in the binder and the proportions that are bound in the resin.
• the proportion of these extenders in the binder is therefore preferably less than 25% by weight, preferably less than 15% by weight and more preferably less than 10% by weight. In order to achieve a cost saving without having to put an excessive influence on the strength of the mold, the proportion of extenders is chosen according to an embodiment greater than 5 wt .-%.
• the furan no-bake binders may further contain water.
• the proportion of water is preferably chosen as low as possible.
• the proportion of water in the binder is preferably less than 20% by weight, preferably less than 15% by weight. From an economic point of view, an amount of water of more than 5% by weight in the binder can be tolerated.
• Resoles are mixtures of hydroxymethylphenols which are linked via methylene and methylene ether bridges and by reaction of aldehydes and phenols in a molar ratio of 1: ⁇ 1, if appropriate in the presence of a catalyst, for example a base see catalyst, are available. They have a molecular weight M w of ⁇ 10,000 g / mol.
• phenolic resins For the preparation of the phenolic resins, all conventionally used phenols are suitable, with phenol being particularly preferred.
• the aldehyde component used is preferably formaldehyde, in particular in the form of paraformaldehyde.
• Alternative phenols and aldehydes have already been explained in connection with the polyurethane binders. The corresponding passages are referred to.
• the binders may contain other customary additives, for example silanes as adhesion promoters.
• Suitable silanes are, for example, aminosilanes, epoxysilanes, mercaptosilanes, hydroxysilanes and ureidosilanes, such as ⁇ -hydroxypropyltrimethoxysilane, ⁇ -aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, ⁇ -mercaptopropyltrimethoxysilane, ⁇ -glycidoxypropyltrimethoxysilane, ⁇ - (3,4-epoxycyclohexyl) trimethoxysilane, N- ⁇ - (aminoethyl) - ⁇ -aminopropyltrimethoxysilane.
• silane is added to the binder in a proportion of 0.1 to 3% by weight, preferably 0.1 to 1% by weight.
• the binders may also contain other conventional components, such as activators or plasticizers.
• the molding material mixture in addition to the refractory molding material, the binder and optionally the catalyst may contain other conventional ingredients.
• exemplary further constituents are iron oxide, ground flax fibers, wood flour granules, ground coal or clay.
• the molding material mixture is then shaped by conventional methods into a basic shape or a part of a basic shape and optionally hardened. If appropriate, the basic shape can then be completely or partially assembled and the mold cavity provided in its basic form can be coated in its entirety or in sections with the sizing composition described above. For this purpose, conventional methods can be used.
• the sizing composition can be applied, for example, by dipping, flooding, brushing or by spraying.
• the mold When immersed as an application method, the mold, in the mold cavity of which optionally a primer coating has been applied, immersed for about 2 seconds to 2 minutes in a container which is filled with a ready-to-use, inventive sizing composition. The mold is then removed from the sizing composition and excess sizing composition drained from the mold. The time taken to drain the excess sizing composition after dipping depends on the flow behavior of the sizing composition used.
• the Schlichtezu ⁇ composition is filled in the diluted state to push boiler.
• the sizing can be pressed into a spray gun via the overpressure to be set, where it is sprayed with the aid of separately adjustable atomizing air.
• the conditions are preferably chosen so that the pressure for size composition and atomizing air is adjusted to the gun such that the sprayed size composition still wet on the mold or the core, but gives a uniform application.
• the carrier liquid contained in the sizing is subsequently evaporated ⁇ stannum, so that a dry size coat is obtained.
• a drying process all conventional drying drying such as drying in air, drying with dehumidified air, drying with microwave or infrared radiation, drying in a convection oven, and similar methods.
• the coated mold at 100 to 250 ° C, preferably at 120 to 180 0 C, dried in a convection oven.
• the sizing composition according to the invention is preferably dried by burning off the alcohol or alcohol mixture.
• the coated casting mold is additionally heated by the heat of combustion.
• the coated casting mold is dried in the air without further treatment.
• the sizing layer can then be further cured, for example by irradiation with UV radiation, if a corresponding curable binder is included in the sizing composition.
• the size can be applied in the form of a single layer or in the form of several layers arranged one above the other.
• the individual layers may be the same or different in their composition.
• a base coat can be made from a commercially available size which does not contain a metallic additive according to the invention.
• a primer coating for example, water-based or alcohol-based sizing can be used.
• the layer which later comes in contact with the liquid metal is always made from the size of the invention.
• each individual layer may be after the application entirely or partially getrock ⁇ net.
• the coating prepared from the sizing composition preferably has a dry film thickness of at least 0.1 mm, preferably at least 0.2 mm, more preferably at least 0.45 mm, most preferably at least 0.55 mm.
• the thickness of the coating is chosen to be less than 1.5 mm.
• the dry film thickness is in this case the layer thickness of the dried coating, which was obtained by Trock ⁇ NEN of the sizing composition by substantially complete removal of the solvent component, and optionally followed by curing.
• the dry layer thickness of the base coat and the top coat are preferably determined by measurement with the wet film thickness comb.
• the casting mold can then be completely assembled.
• Another object of the invention relates to the use of the casting mold described above for the production of a casting.
• a casting mold is first provided.
• This may be a lost mold made as described above from a refractory material, such as quartz sand, and a binder, or even a permanent mold commonly used to make pipes, bearings or sleeves, the mold cavity having the shape described above Sizing composition was lined.
• the mold has a protective coating on at least the surfaces which contact the liquid metal, which isolates the liquid metal from the mold and which can positively influence the surface finish of the casting.
• liquid metal is introduced, preferably iron or an iron alloy.
• the liquid metal is then allowed to solidify into a casting and then the casting is separated from the casting mold.
• applied method In lost molds, the mold is mechanically destroyed, for example by shaking.
• the casting is erformen at Dau ⁇ drawn by conventional methods from the mold.
• Another object of the invention relates to a mold having a mold coating which has been prepared from the size described above.
• a mold advantageously has an insulation between the liquid metal and the casting mold, whereby the thermal load of the casting mold is reduced during the casting process and thereby increases the durability of the casting mold.
• the mold coating a metallic additive that can positively influence the surface properties of the cast part, in particular the formation of a pitted surface on the casting ⁇ piece pushes back.
• Molds having a topcoat made from the sizing composition of the present invention are used, inter alia, to make wind force scars, grinding bowls, engines and engine components, machine beds and turbines, general machine components or dies.
• the core size used in the examples below has the composition given in Table 1.
• Table 1 Composition of the size
• the cast molding stock was prepared as follows: isopropanol is charged and the clay is digested for at least 15 minutes using a high shear stirrer. Subsequently, the refractory components, pigments, manganese and dyes are stirred for at least 15 minutes until a homo ⁇ gene mixture is formed. Finally, ethanol, rheological additives and binders are stirred in.

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• 2009
  • 2009-05-27 MX MX2010012994A patent/MX2010012994A/es active IP Right Grant
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