Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/56—Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
  • B29C33/60—Releasing, lubricating or separating agents
  • B29C33/62—Releasing, lubricating or separating agents based on polymers or oligomers
  • B29C33/64—Silicone
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
  • B22C1/14—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for separating the pattern from the mould
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/18—Finishing

Definitions

• This disclosure relates to a process for producing molds for foundry purposes, in particular, mask molds, sand cores and parts thereof, and compositions and apparatuses suitable for use in this process.
• heat-resistant molds which can be produced, in particular, from a particulate, refractory material and a binder are required.
• Molds used for foundry purposes are frequently mask molds which can be produced by the Croning process (named for its inventor Johannes Croning).
• mask molds consist of two halves which when placed together form a mold material shell corresponding to the contour of the model.
• Mask molds and parts thereof are preferably produced from mixtures of sand and synthetic resin using heated modeling apparatuses. The mixture is introduced into a hollow model whose inner cavity determines the contours of all surfaces of the mold to be produced or of the mold part to be produced.
• the synthetic resin binder cures to form a self-supporting, mask-like mold of preferably low thickness which defines the exterior contour of the product to be cast.
• this mold can be, for example, backfilled with granular material.
• cores which can be arranged within a casting mold and whose exterior shape corresponds to the interior contour of the product to be cast are required.
• the core may thus be a constituent of a mold. After casting, the core can be removed again (dissolved out) from the cast product.
• cores are usually produced from a particulate, refractory material and a binder.
• a binder for example, sand admixed with binder (known as core sand) can be introduced under defined pressure and at defined temperature into a core box (an apparatus which generally consists of two parts of the mold or mold halves which during use enclose at least one interior cavity known as a mold cavity having the shape of the core to be manufactured).
• core box an apparatus which generally consists of two parts of the mold or mold halves which during use enclose at least one interior cavity known as a mold cavity having the shape of the core to be manufactured.
• the finished core which on the basis of its composition is usually referred to as a sand core
• a sand core can be removed from the core box and used for its intended purpose.
• mask molds and cores usually have to be made from very high quality materials, e.g., from pure silica sand.
• the particle size of the materials is preferably selected so that the surfaces of the cast products do not become too rough.
• organic binders such as liquid phenolic, furan and amino resins (or a combination thereof) are used as binders.
• a hardener such as ammonium stearate, a mixture thereof with a suitable particulate, refractory material can cure in a very short time at temperatures in the range from 200° C. to 270° C.
• inorganic binders have been used to an increasing extent in recent times. Possible binders of this type are, in particular, water glass, magnesium sulfate, sodium phosphate, clays, montmorillonite, glauconite, kaolin, aerogels, cement or gypsum plaster.
• sheet minerals in particular, sheet silicates, are generally also suitable as inorganic binders.
• a Quickpad is an antiadhesion sticker which can, for example, be based on a Teflon layer. This has to be manually stuck on in the interior cavity and removed again and replaced when the effect diminishes, which is associated with a relatively high outlay.
• Quickpads have only limited use since the very complex contours occurring in some regions of the interior cavities may make their use impossible.
• Quickpads have only limited thermal stability and are therefore unsuitable for use in heat-curing processes.
• mold release agents in particular, ones based on wax
• Such mold release agents form a liquid film on walls of the interior cavities.
• a process for producing a mold including introducing a composition including a particulate, refractory material and a binder into a hollow model having an interior cavity which determines contours of all surfaces of the mold or a mold part, wherein the model includes at least two separate parts to permit removal of the mold, and applying a second composition containing at least one organosilicon component to at least one of the separable parts before use.
• Our process produces molds for foundry purposes, particularly preferably mask molds, cores (in particular, sand cores) and parts thereof.
• the process thus allows production both of molds which define the exterior contour of a product to be cast and of molds which can be used for creating a cavity (cores).
• a composition comprising a particulate, refractory material and a binder is introduced, in particular blown, into a hollow model.
• the binder is generally immediately cured, whereupon the molds produced can be removed.
• the interior cavity of the hollow model or its shape determines the contours of all surfaces of the mold to be produced or the core to be produced.
• the mold itself includes at least two parts which can be separated from one another to permit removal of the mold.
• preference is given to using a conventional mold box or a conventional mold flask, as are known in the art.
• a process for producing molds for foundry purposes is particularly characterized in that a composition containing at least one organosilicon component and preferably at least one solvent is applied to at least one of the separable parts before it is used.
• a process for producing cores for foundry processes preferably comprises:
• composition comprising the organosilicon component is preferably applied in such a way that the walls of the interior cavity are at least partly, preferably completely, covered by the layer or coating.
• the composition is applied in the regions which are particularly severely mechanically stressed during introduction of the composition comprising the particulate, refractory material and the binder, i.e., particularly the regions which are located opposite the at least one feed opening and are thus struck directly by the composition during shooting-in.
• the composition is preferably applied by spraying on or dipping. It is naturally necessary to use a composition having a suitable consistency in each case.
• the properties required for this and also other properties of the composition can be adjusted by addition of appropriate additives such as thickeners, rheological additives and the like. Suitable additives are known and require no detailed explanation.
• composition comprising the organosilicon component can be cured immediately after application. Curing of the composition is preferably carried out thermally, more preferably at temperatures in the range from room temperature to 350° C., particularly preferably from 20° C. to 300° C., in particular from 30° C. to 200° C.
• the composition preferably comprises at least one constituent which can be crosslinked thermally.
• This can also be, in particular, the at least one organosilicon component.
• curing can also be effected by electromagnetic radiation.
• electromagnetic radiation having wavelengths in the UV and/or IR region is particularly preferred.
• the composition preferably comprises at least one constituent which can be crosslinked by radiation.
• the at least one organosilicon component can have side chains which can be crosslinked by radiation (in particular, chains having ethylenic double bonds).
• components which can be crosslinked thermally and components which can be crosslinked by radiation can both be present in the composition, in which case it is not necessary for all components to be organosilicon components.
• polyester resins can also be preferred as a constituent of the composition.
• the organosilicon layer or coating produced in this way has an excellent release function and effectively prevents direct contact of the composition comprising the particulate, refractory material and the binder with at least the critical wall regions of the interior cavity.
• the layer or coating can therefore also be referred to as release layer. It has high nonwettability. In addition, it is characterized, in particular, by an extraordinarily high abrasion resistance and very good adhesion properties.
• the particulate, refractory material is particularly preferably sand, especially silica sand.
• binders for the particulate, refractory material it is possible to use the organic binders mentioned at the outset.
• inorganic binders optionally in combination with one or more organic binders.
• Possible inorganic binders are, in particular, water glass, magnesium sulfate, sodium phosphate, clays, montmorillonite, glauconite, kaolin, aerogels, cement, gypsum plaster, sheet minerals such as sheet silicates and combinations of the components mentioned.
• the at least one organosilicon component is preferably a crosslinkable component and thus comprises compounds which can undergo reactions with one another on irradiation and/or on heating. It particularly preferably comprises a silane or a siloxane or a crosslinkable silicone compound. Combinations of silanes and siloxanes or silicones can also be used.
• silanes are organofunctional silanes such as aminosilanes, epoxysilanes and methacryloxysilanes and isocyanatosilanes.
• the methacryloxysilanes are, in particular, radiation-crosslinkable silanes which can be cured, for example, by UV radiation as has been discussed above.
• Suitable siloxanes and silicones are, for example, polysiloxanes such as, in particular, polydialkylsiloxanes (in particular, polydimethylsiloxane), polyorganosiloxanes, epoxysilicones and polyether silicones. These should each have crosslinkable groups.
• the crosslinkable groups can be, for example, groups such as free hydroxy groups which can undergo a condensation reaction or, for example, alkoxy groups from which free hydroxy groups can be formed.
• the composition has further organosilicon components.
• alkoxysilanes are preferably present.
• alkylalkoxysilanes such as trimethylethoxysilane or trimethylmethoxysilane.
• a composition thus contains, in preferred form, at least one of the above-mentioned crosslinkable organosilicon compounds and additionally at least one alkoxysilane.
• the composition can contain at least one silane having halogen-containing, preferably fluorine-containing, side chains, in particular, as at least one crosslinkable organosilicon component.
• This is particularly preferably an alkoxysilane having halogen-containing, in particular, fluorine-containing, side chains, particularly preferably tridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane.
• a composition which can be used can also comprise at least one further crosslinkable organic component which is not of an organosilicon nature, in particular, a polyester component.
• the at least one crosslinkable organosilicon component and the at least one further crosslinkable organic component are present in combination as silicone polyester resin in the composition.
• Suitable silicone polyester resins are, for example, commercial polyester-modified methyl-phenyl-silicone resins which are also suitable for coating of baking molds for easier removal of bakery products from molds.
• the composition comprising the at least one organosilicon component has one or more mold release agents, in particular, at least one release oil.
• the mold release agent is preferably a linear or branched polysiloxane, in particular, a polysiloxane of the formula RO—[R′ 2 Si—O] n —R, where R and R′ are, independently of one another, an alkyl radical having from 1 to 8 carbon atoms or an aromatic radical having from 6 to 20 carbon atoms.
• inorganic particles in particular, particles having particle sizes in the range from nanometers to microns, can also be present in the composition comprising the at least one organosilicon component.
• the nature of the inorganic particles is not critical and all ceramic particles are fundamentally suitable.
• silicate particles are particularly preferred. It has surprisingly been found that the presence of such particles significantly increases the abrasion resistance of the release layer.
• a composition comprising the at least one organosilicon component has components suitable as crosslinkers.
• Customary crosslinkers are known to those skilled in the art. Particular preference is in the present case given to using triethoxysilane (TEOS) or triacetoxymethylsilane.
• a composition can also have a catalyst, in particular, at least one condensation catalyst.
• a catalyst in particular, at least one condensation catalyst.
• This can be, for example, an acid such as hydrochloric acid or sulfuric acid.
• the abovementioned solvent is preferably an organic solvent, in particular, at least one alcohol, ether and/or ester.
• Nonpolar solvents such as petroleum spirit can also be used.
• the nature of the solvent is in principle not critical.
• An apparatus for producing molds for foundry purposes is particularly suitable for producing mask molds and sand cores. It has at least one part which is provided with an organosilicon layer or coating, in particular, a cured organosilicon layer or coating.
• the apparatus is accordingly itself preferably a mold.
• the layer or coating is preferably produced from a composition containing at least one organosilicon component and preferably at least one solvent, as has been comprehensively described above.
• the layer or coating has a thickness in the range from 1 ⁇ m to 100 ⁇ m, in particular, from 1 ⁇ m to 20 ⁇ m.
• the at least one part preferably consists at least partly, preferably also entirely, of metal and/or plastic.
• the layer or coating is particularly preferably permanently or at least semipermanently bound to the at least one part of the mold.
• the bond is so strong that the layer cannot be detached without destruction.
• the layer or coating forms an organosilicon matrix in which inorganic particles can be embedded in preferred forms.
• a polyester-modified methyl-phenyl-polysiloxane resin admixed with a release substance for example, a commercial polyester-modified methyl-phenyl-polysiloxane resin suitable for removal of sugar-containing bakery products from molds
• a release substance for example, a commercial polyester-modified methyl-phenyl-polysiloxane resin suitable for removal of sugar-containing bakery products from molds
• methoxypropyl acetate as solvent possibly colored blue with ultramarine blue extra dark
• the alcohol is placed in a 1000 ml glass flask.
• the silane having fluorine-containing side chains tridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane
• the TEOS and the trimethylethoxysilane are added in succession over a period of one hour from a dropping funnel while stirring vigorously.
• the hydrochloric acid is then added dropwise. After stirring at room temperature for 4 hours, the hydrolysis product is ready to be used and can be applied.
• the alcohol is placed in a 100 ml glass flask.
• the silane having fluorine-containing side chains tridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane
• the colloidal silicate dispersion silicate dispersion in isopropanol having a particle size of about 13 nm and a solids content of 30%
• the sulfuric acid is then added dropwise. After stirring at RT for 4 hours, the product is ready to use and can be applied.
• the parts to be coated are preferably cleaned with isopropanol.
• the parts can also be cleaned by sand blasting.
• the product A from Example 1 is applied by means of a spray gun (e.g., SATA minijet 4 HVLP having a 0.8 nozzle) at 2 bar.
• the layer thicknesses achieved are in the range from 3 ⁇ m to 75 ⁇ m.
• Curing is carried out (in a drying oven) at from 150° C. to 230° C. over a period of from 1 to 4 h.
• the products B and C from Examples 2 and 3 are applied by means of a cloth (preferably cleanroom cloth, e.g., Betawype TX 2009 from Texwype) and rubbed in (polished).
• Thermal setting is carried out at 200° C. by means of a hot air blower over a period of from 1 to 3 minutes, preferably 90 s, or (in a drying oven) 1-4 h at 150-190° C., preferably 2 h at 190° C.
• a core flask having 20 engravings was treated with the product A.
• the critical regions (places opposite the shooting-in nozzles for the core mold material) were treated with the product.
• the product was applied and allowed to cure at room temperature for 24 hours.
• the core flask was then used in mass production. It was found that the time until critical caking of core mold material occurred could be tripled.
• a mold box made of metal having two engravings was treated with the product A.
• the critical regions (places opposite the shooting-in nozzles for the core mold material) were treated with the product.
• the product was applied and allowed to cure at room temperature for 24 hours.
• the second engraving was covered by sticking on a Quickpad (adhesive film having a non-stick effect).
• the mold was then used in mass production. It was found that the time until critical caking of core mold material occurred is identical for the two methods.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (5)

Publications (1)

Family

ID=40451304

Family Applications (1)

Country Status (13)

Cited By (4)

Families Citing this family (14)

Citations (10)

Family Cites Families (20)

• 2008
  • 2008-12-19 BR BRPI0821563A patent/BRPI0821563A2/pt not_active IP Right Cessation
  • 2008-12-19 CN CN2008801218302A patent/CN101952094A/zh active Pending
  • 2008-12-19 WO PCT/EP2008/010971 patent/WO2009083201A1/de not_active Ceased
  • 2008-12-19 HU HUE08868453A patent/HUE025922T2/en unknown
  • 2008-12-19 KR KR1020107016138A patent/KR101651692B1/ko not_active Expired - Fee Related
  • 2008-12-19 JP JP2010538487A patent/JP2011506148A/ja active Pending
  • 2008-12-19 ES ES08868453.5T patent/ES2552280T3/es active Active
  • 2008-12-19 RU RU2010127337/05A patent/RU2488485C2/ru active
  • 2008-12-19 EP EP08868453.5A patent/EP2244870B1/de not_active Not-in-force
  • 2008-12-19 US US12/808,720 patent/US20110036528A1/en not_active Abandoned
  • 2008-12-19 MX MX2010006959A patent/MX341207B/es active IP Right Grant
  • 2008-12-19 PL PL08868453T patent/PL2244870T3/pl unknown
• 2010
  • 2010-06-18 ZA ZA2010/04344A patent/ZA201004344B/en unknown

Patent Citations (10)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events