EP4021662A1 - Procédé de production de noyaux et de moules en fonte au sable - Google Patents

Procédé de production de noyaux et de moules en fonte au sable

Info

Publication number
EP4021662A1
EP4021662A1 EP20771195.3A EP20771195A EP4021662A1 EP 4021662 A1 EP4021662 A1 EP 4021662A1 EP 20771195 A EP20771195 A EP 20771195A EP 4021662 A1 EP4021662 A1 EP 4021662A1
Authority
EP
European Patent Office
Prior art keywords
molding material
binder
component
sand
catalysts
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20771195.3A
Other languages
German (de)
English (en)
Inventor
Sandra ESCHRICH
Daniel HOLSTEIN
Thomas GALLERT
Tina HERTEL
Jörg GEBEL
Robin GOLDACKER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bindur GmbH
Original Assignee
Bindur GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bindur GmbH filed Critical Bindur GmbH
Publication of EP4021662A1 publication Critical patent/EP4021662A1/fr
Pending legal-status Critical Current

Links

Classifications

    • 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
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
    • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
    • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • B22C1/2273—Polyurethanes; Polyisocyanates
    • 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

Definitions

  • the invention relates to a method for producing cores and molds using the sand molding method.
  • the method is particularly suitable for producing foundry molded parts from molded materials, comprising two-component polyurethane binders, one or more thermally activated catalysts and natural and / or ceramic sands.
  • the molding materials are hardened in warm and hot hardening core and mold manufacturing processes. The hardening of the molding material is promoted by thermally induced catalyst activation.
  • molding material mixtures are generally produced by thoroughly mixing a binding agent with a molding base material, introduced into a model and, after the molding material has hardened, stripped out. After adding a core (package) and molded part halves, the casting with metallic melt takes place.
  • Inorganic or organic binders are used to bond the basic molding material, for example quartz sand.
  • Swellable clay minerals such as bentonite or aqueous alkali silicate solutions, in particular modified water glasses, are used as inorganic binders.
  • organic binders phenolic, furan or urea resins and condensates thereof with formaldehyde or mixtures thereof are used, but also phenolic resin-based two-component polyurethanes.
  • a wide variety of processes are used to process molding materials into “lost forms” and cores, which can basically be divided into hot-curing and cold-curing processes. These are to be used in the following both in With regard to their process parameters as well as the binders used for this purpose, they are described and compared with one another. What these processes have in common is that the flowable molding material is first introduced into a mold by hand or by means of compressed air during core shooting. The processing step of the hardening, on the other hand, differs in all the processes described.
  • a period of 10 to 90 minutes is waited after molding, after which the molding material has hardened and can be removed from the model (pep-set or no-bake process).
  • Furan resins, phenolic resins or polyurethanes can be named as suitable binder classes for this purpose.
  • the cycle times have to be reduced to a few seconds to a minute, which is achieved with cold curing, for example by gassing with an amine in the cold box process.
  • Thermosetting processes are also used to reduce cycle times and generally differ in terms of the temperature range or the type of heat supply.
  • Organic and inorganic binders are available for the various warm and hot-curing processes.
  • a distinction is first made between hot-box and warm-box processes because, depending on the binder used, there are different curing temperatures and thus different tool requirements. In both processes, a heatable core box or a heatable model is used, which are made of metal at a relatively high cost.
  • binders based on phenolic or furan resins are used, which harden at temperatures of up to 300 ° C.
  • the warm box process is only carried out at around 150 ° C with specially additized furan resins as a binder.
  • phenol-based hot box binders are condensates of phenol, urea, formaldehyde and a low molecular weight alcohol to which aqueous ammonium chloride solution is added as hardener, as described, for example, in DE 1569023 C3. Mixtures of acidic latent hardeners and hexamethylenetetramine are also possible. By masking the hardener, the reaction actually only starts when it is heated.
  • the hardening agents are adducts of strong acids with weakly basic or polar substances, for example urea or polyols, or heavy metal salts of organic acids, as is known, for example, from DE 3738902 A1.
  • Hexamethylenetetramine takes on the role of an additional inhibitor in order to further extend the processing time of the molding material mixture.
  • Condensation products of aromatic amines with aldehydes, as also described in DE 3032592 C2 are also suitable as inhibitors.
  • Hot-box binders based on phenol-resol resins mean that the cores adhere strongly to the mold, even with the use of a release agent, and can hardly be detached without damage, as is evident from DE 1570203 A, for example.
  • Furan resin-based hot box systems contain dihydroxymethylated furan or the corresponding polymers which, as is known from US Pat. No. 7,125,914 B2, also cure with latent acid catalysts at a temperature of 205 ° C. in 20 to 40 seconds.
  • Such a binder system is known from DE10031 954 A1, which discloses that when using 2% binder to harden the molding material, 20 seconds to two minutes at a mold temperature of 200 ° C. are necessary.
  • Another method of avoiding phenol and formaldehyde emissions is to harden molding materials with epoxy resins and / or epoxy novolak resins and dicyandiamide or imidazoles as latent catalysts. This is described, for example, in EP 0423780 A2.
  • the test specimens can be removed after 20 seconds to two minutes at 150 ° C.
  • Furan resin condensates with urea can release nitrogen, which leads to gas-induced casting defects, so-called pinholes.
  • systems made of phenol resole resins in alkaline solution have been developed which are cured in 30 to 90 seconds at 230 to 260 ° C without the addition of a catalyst.
  • Such systems are described, for example, in WO 88/08763 A1.
  • Another advantage here is the low content of free formaldehyde, but a very hot tool is required and the binder requirement is relatively high at 2%.
  • heat curing is also used, but according to a different principle. Such a method is the subject of GB 876493 A.
  • the basic molding material is coated with a phenol novolak resin to which flexamethylene tetram is additionally added.
  • This free-flowing molding material is poured onto a 250 to 350 ° C warm metal plate, which represents the model, and only sets in one layer.
  • the unbound molding material can be reused. Due to the excellent flowability of the "dry" sand, thin cross-sections and fine contours can be reproduced particularly well in the cast. However, a very high thermal input is necessary here too, and the sand has to be pretreated in a costly manner.
  • waterglass-based, inorganic binders are increasingly being used in foundries. Their molding material strengths are generally lower than those of the organic binders, but their emissions during casting are significantly lower. In addition to flaring by adding liquid esters or gassing with C0 2 , heated tools or hot air are also common.
  • Warm air has the decisive advantage that no expensive, heatable core boxes are necessary, as is the case with the hot box or warm box process, but simple plastic models can be used.
  • the core is heated evenly by warm air. Not only is the outer shell adjacent to the core box heated, because the warm air penetrates the core evenly.
  • a very strongly heated tool that is to say to a temperature> 200 ° C
  • a suitable device for heating air is described, for example, in DE 202006018044 U1.
  • Organic binder systems are also hardened using the hot air process.
  • Suitable binders are aqueous ammonium polyacrylates in combination with metal salts, as is also described in US Pat. No. 4,678,020.
  • the binder is partially decomposed by the warm air, releasing ammonia and forming water-insoluble metal polyacrylates that bind the molding material.
  • the core mold was heated to the same temperature.
  • Generative manufacturing processes are increasingly complementing classic core manufacturing in foundries. Instead of mixing the binder and the basic molding material and putting them into a mold, sand is applied in layers in a box and a binder is applied to the desired areas.
  • the binders are self-curing or thermosetting. The heat input takes place either after the printing is finished by transferring the box into an oven, or directly during the printing process with the help of infrared radiation.
  • a variant is a further development of the croning process, which is described in WO 95/32824 A1 and in which resin-coated sand is applied in layers and the resin is melted on at certain points with an infrared laser beam.
  • a thermal hardening of molding materials can also be done by microwave radiation. From DE 102007027 577 A1 it is known that, particularly with aqueous alkali silicate binders, a significant increase in the strength of the molding material can be achieved.
  • the cores can be hardened both after they have been fired with a core shooter in a microwave oven and by direct production in a special core shooter, as is described in DE 11 2016006377 T5. In the first case, the transport into the furnace represents an additional, error-prone process step. In the second case, however, a special core shooter is required, which represents a high investment barrier in practice.
  • phenol-formaldehyde resins in particular are solidified with isocyanate-containing hardeners in the cold-box process, in which amine gassing results in an almost sudden hardening of the molding material with the formation of a polyurethane addition product, and this is particularly good suitable for an automated core manufacturing process.
  • the cold box process is explained in numerous publications, for example in US 3409579 A, DE 2 162 137 A or DE 1 959023 A.
  • DE 102015 118428 A1 discloses phenol-formaldehyde resin-free binders for foundry molding sands and molding material mixtures made from natural and / or ceramic sands with these binders.
  • the binder is either a one-component binder based on polyurethane and / or polyurea, which is suitable for a multi-phase curing process using water-alcohol mixtures, or as a two-component binder.
  • This two-component binder comprises a component A with an average hydrogen functionality of 2.0 to 3.9 and an average equivalent weight of 450 to 900 g / eq of the starting materials, the starting materials of component A being polyether alcohol mixtures of hydroxyl and / or Represent mercapto groups and / or internal nitrogen-containing individual components, and an isocyanate-containing component B.
  • the binders are Environmentally and health-neutral due to the lack of phenol-formaldehyde resin and aromatic solvents. They are suitable for core and mold production in cold self-curing (Pep-Set) and amine-hardening (Cold-Box) processes.
  • blocked amines containing aldimine groups can be used in two-component polyurethane compositions for use as adhesives, sealants, coatings or potting compounds.
  • Blocked amines are also used in epoxy resins. According to WO 2019/081581 A1, one-component epoxy resin compositions have a longer shelf life.
  • EP 2864435 B1 describes the use of ketimines, enamines, oxazolidines, aldimines and / or imidazolidines as blocked amine catalysts for moisture-curing polymer compositions based on a trialkylsilane-terminated sulfur-containing polymer, which can be used as a sealant for sealing an opening.
  • EP1 990387 A1 describes catalysts containing tertiary amine groups for use in polyurethane hotmelt adhesives with which plastics containing plasticizers can be bonded.
  • WO 2011/095440 A1 describes the use of blocked tertiary amines, more precisely 1,8-diazabicyclo [5.4.0] undec-7-en (DBU), 1,4- Diazabicyclo [2.2.2] octane (DABCO) and / or 1, 5-diazabicyclo [4.3.0] non-5-en (DBN), as latent catalysts that operate at switching temperatures between 30 and 60 ° C or 80 to 150 ° C, for the production of polyisocyanate polyaddition products, polyurethane cast elastomers and for the production of screens, pigs, rollers, wheels, rollers, scrapers, plates, cyclones, conveyor belts, doctor blades, couplings, seals, buoys and pumps.
  • similar products are produced using amidines blocked with monocarboxylic acid as latent catalysts for polyisocyanate polyaddition products.
  • Thermolatent catalysts based on tertiary amines which are catalytically active in the range from 50 to 120 ° C, can be used in so-called sheet molding compounds for the production of fiber composite components. This is also known from WO 2017/149031 A1, among other things.
  • No. 2,891,025 A describes quaternary imidazolium salts which serve as polymerizable starting materials which are used in the form of homo- and co-polymer products as plastics, coatings, adhesives, laminations, casting resins or fiber-forming materials.
  • No. 2,800,487 A describes polyoxyalkylene-substituted heterocyclic amines and their ammonium salts as surface-active detergents.
  • latent tetravalent tin catalysts represent an alternative to toxic mercury catalysts and are mainly used for the production of foams.
  • tin or bismuth catalysts which are complexed with an excess of mercapto compounds and thus blocked, are described in WO95 / 29007 A1.
  • DE 102014 110 189 A1 describes a cold box binder consisting of Phenolic resin, polyisocyanate and a blocked tertiary amine or amidine described as a cocatalyst.
  • This co-catalyst is not activated thermally, but develops its effect in conjunction with the tertiary, highly volatile amine, for example triethylamine, which is used as a catalyst according to the cold box process. This allows the consumption of the volatile amine to be reduced.
  • the organic binders described above consist largely of phenolic resins or furfuryl alcohols. Their monomers are mostly toxic and / or carcinogenic and are released during processing, but at the latest during thermal decomposition during casting, and therefore represent a burden for employees and the environment.
  • the object on which the invention is based is to develop a method for the production and processing of molded materials with a binder and a suitable catalyst which promotes hardening of the molded material with the supply of heat and which allows the molded material to be treated by means of moderate thermal input, similar to the warm box. or to cure hot air processes and achieve fast cycle and disconnection times that come close to those of the amine gas curing cold box process.
  • Another concern of the invention is to overcome disadvantages relevant to the environment and occupational health and safety, which result from the use of molding materials containing classic organic binders, which are cured in the warm / hot box and / or warm / hot air process.
  • this concerns the avoidance of the release of emission-relevant substances such as volatile compounds (VOC), phenols, formaldehyde or hydrolytic breakdown products such as aldehydes or ketones.
  • VOC volatile compounds
  • phenols formaldehyde or hydrolytic breakdown products
  • aldehydes or ketones ketones
  • Sand molding process includes at least the following steps:
  • thermosetting molding material the molding material being formed from at least the following components:
  • a two-component, phenol- and formaldehyde-free binder based on polyurethane containing a resin component as a mixture of two or more isocyanate-hydrogen-active compounds with hydroxyl and / or mercapto and / or amino and / or carbamide groups with an OH -, SH and NH functionality of 1.5 to 8 and equivalent weights of 9 to 2000 g / eq of the individual components and an average H functionality of 1.8 to 4.0 and an average equivalent weight of 90 to 200 g / eq the resin component and a hardener component with one or more diisocyanates or polyisocyanates,
  • one or more thermally activatable catalysts the activation temperatures of which are between 50 and 170 ° C, having the polyurethane reaction promoting Brönsted bases and / or Lewis acids and their associated blocking agents, and ⁇ one or more refractory pourable fillers / fillers,
  • thermosetting molding material in the molding tool in the hot box method or in the hot air method at temperatures of the heatable molding tool or the hot air between 90 and 170 ° C, preferably between 100 and 130 ° C, and
  • the mold used is made of plastic, wood or metal. in the In the case of a core box, this generally consists of two halves, the cavity of which forms the core. The core forms the cavity in the casting.
  • thermosetting molding material can consist of one or more refractory, pourable fillers from 95.9 to 99.6%, a binder from 0.3 to 4.0% and one or more thermally activated catalysts from 0.002 to 0.1% in a batch or continuous mixers.
  • the flowable molding material is advantageously introduced into the molding tool by applying compressed air, preferably at 2 to 6 bar, to the storage vessel in which the molding material is temporarily connected to the molding tool via suitable openings.
  • the molding material can be introduced into the tool by manual transfer and compression.
  • thermosetting molding material is hardened in the process according to the invention by heating the molding tool used to 90 to 170.degree. C. or rinsing the molding material with hot air at 90 to 170.degree.
  • the flushing pressure is preferably 0.5 to 6 bar.
  • the molding tool can be opened by machine or by hand and the mold part can be removed using a device or by hand.
  • balanced combinations of different aliphatic and / or cycloaliphatic compounds which are hydrogen-active with respect to isocyanate are preferably used for the two-component systems in the resin component, these compounds being polyether alcohols, reactive and non-reactive polymer polyols, polycaprolactones, polyether polyester alcohols , Polythiols, amino polyether alcohols, di- and higher-functional alcohols, amines, Carbamide compounds. Two or more individual components of one or more of these substance classes are incorporated into the resin component.
  • the individual constituents of the resin component are selected so that there is an average H functionality of 1.8 to 4.0, preferably 2.2 to 3.5.
  • the combination of two-functional with higher-functional compounds has proven to be advantageous for optimal crosslinking, with an optimal average functionality being sought.
  • Di-, tri- and tetra-functional polyether alcohols are particularly suitable as crosslinking polyols for the production of the resin component used in the process according to the invention.
  • Such polyols are for example
  • Suitable polycaprolactones are, for example, Placcel® 205, 305 and 410 from Daicel®, Durez® Ter S 1063-72 and S 2006-120 from Sumitoma Bakelite® or Capa® 3031, 3022 and 2043 from Ingevity®.
  • NFI-functional compounds can be any suitable polycaprolactones.
  • Polyether diamines such as Jeffamine® D-400 and D-230 from Fluntsman® or simple structures such as diglycolamine can be used.
  • Polyhydric short-chain alcohols preferably with a maximum molecular weight of 200 g / mol, are diols such as ethylene glycol, 1,3-propanediol, 2-butyl-2-ethylpropanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,4-butanediol , Diethylene glycol, 1,5-pentanediol, 2,2,4-trimethylpentane-1,3-diol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,6-flexanediol and 2 -Ethylhexane-1,3-diol, triols such as glycerol, trimethylol
  • the binders are processed with or without additional catalytic support.
  • Suitable catalysts are organotin, organobismuth, organozinc, organopotassium and organoaluminum compounds and also tertiary or quaternary nitrogen-containing substances such as dimethylcyclohexylamine, N-substituted pyrrolidones, N-substituted imidazoles, diazabicyclooctane and triazine derivatives.
  • Suitable metal-based catalysts are, for example, the Kosmos® and DABCO® grades from Evonik®, catalysts from TIB®, K-Kat® products from
  • the hardener component of the binder of the molding material consists of mixtures of one or more isocyanates with thinners and additives that ensure processability, the isocyanate content preferably being in a balanced stoichiometric ratio to the hydrogen-active compounds of the resin component.
  • Suitable isocyanates of the hardener component of the molding material according to the invention are oligomers or polymeric derivatives of the basic type of 2,4'- and 4,4'-diphenylmethane diisocyanate and / or oligomers or polymeric variants of the type of 2,4'- and 4, 4'-dicyclohexylmethane diisocyanate and / or oligomeric or polymeric derivatives of hexamethylene diisocyanate with optionally completely or partially blocked isocyanate groups and / or isophorone diisocyanate and / or its derivatives, as well as the aromatic, aliphatic and cycloaliphatic isocyanates prepared in a prepolymer process and their Oligomers and polymers.
  • Oligomeric and polymeric derivatives of isocyanates include carbodiimides, isocyanurates, biurets, uretdiones and uretonimines.
  • Common blocking agents for isocyanates which can be split off again under the action of heat, are phenol, cresol, acetoacetic ester, diethyl malonate, e-caprolactam and butanone oxime.
  • the isocyanates preferably have at least functionality 2 and are liquid at room temperature.
  • the aforementioned prepolymers are made by a pre-crosslinking of a stoichiometric deficit of di- or polyfunctional polyols with suitable aliphatic and / or aromatic and / or cycloaliphatic Isocyanates produced, with a residual content of free isocyanate groups between 5 and 35%, particularly preferably between 6 and 30%, preferably resulting.
  • such prepolymers must have a processing-friendly viscosity which ensures thorough mixing with the basic molding material and is therefore a maximum of 900 mPas, but preferably 300 to 600 mPas, at 20 ° C. All viscosities specified in connection with the present invention were determined using a rotary viscometer in accordance with DIN 53019.
  • Suitable isocyanates for binders of the molding material in the process according to the invention include Lupranate® from the product range from BASF®, Desmodur® types from Covestro®, Voranate® and Isonate® from Dow Chemical®, Vestanate® from Evonik®, the Suprasec® series from Fluntsman®, Tolonate® from Vencorex®, Polurene® and Flydrorene® from Sapici® or Ongronate® from Wanhua®.
  • suitable isocyanates include in particular Lupranat® M 70 R, Lupranat MM® 103, Lupranat M® 105, Lupranat® MIP, Lupranat® M 10 R, Lupranat® M 20 S, Desmodur® 44 V 70 L, Desmodur® 44 V 20 L, Desmodur® CD-S, Desmodur® DN, Desmodur® I, Desmodur® W / 1, Vestanat® IPDI, Vestanat® H12MDI, Vestanat® TMDI, Vestanat® HT 2500 / LV, Suprasec® 2030, Suprasec® 2085 , Tolonate® HDB LV, Tolonate® HDT LV, Ongronat® 3800, Ongronat® CR-30-20, Ongronat® CR-30-40, Ongronat® CR-30-60.
  • the binder components, ie resin and hardener, of the molding materials used in the process according to the invention are preferably supplemented by thinners with the aim of good processability.
  • thinners are, for example, fatty acid esters based on renewable raw materials, such as transesterification products from vegetable oils, especially their methyl, ethyl, propyl, isopropyl, butyl and isobutyl esters.
  • Synthetic mono-, di- and tricarboxylic acid esters, organosilicates, sulfonic acid esters and / or largely are also suitable aromatic-free fractions from petroleum processing, phosphoric acid esters, cyclic and non-cyclic carbonates and / or non-hydroxy-functional terminal polyethers.
  • fatty acid esters from natural oils are the rapeseed methyl ester from Giencore or other established biodiesel manufacturers, the palm and
  • Soy methyl ester from Cremer the Priolube® types from Croda®, the DUB® products from Stearinerie Dubois®, and the RADIA® esters from Oleon®.
  • Suitable organosilicates in particular alkyl silicates and alkyl silicate oligomers, are, for example, tetraethyl silicate, tetra-n-propyl silicate, as well as mono-, di- and
  • thermally activatable amine catalysts and / or metal-based catalysts can be used in the process according to the invention to harden the molding material in a heated core box according to the warm box process or in the unheated core box by introducing warm air . These are then presented as part of the Flarz component in this and / or can be added to the molding material as an individual component.
  • a thermally activated catalyst releases the catalytically active species at temperatures of 50 to 170 ° C.
  • the resulting polyurethane reaction of the two-component binder ensures immediate hardening of the molding material and enables the hardened molding material to be removed from the core box.
  • the reaction rate is many times higher than with other common polyurethane catalysts or without a catalyst at all. In contrast to the common catalysts, remains with Use of thermally unstable catalysts largely unaffected the processing time at room temperature.
  • the thermally activated catalysts have, for example, 1,8-diazabicyclo [5.4.0] undec-7-en (DBU), 1,4-diazabicyclo [2.2.2] octane (DABCO), bis ( 2-dimethylaminoethyl) ether, imidazole, piperazine, guanidine or morpholine derivatives.
  • DBU 1,8-diazabicyclo [5.4.0] undec-7-en
  • DABCO 1,4-diazabicyclo [2.2.2] octane
  • bis ( 2-dimethylaminoethyl) ether imidazole
  • piperazine guanidine or morpholine derivatives.
  • Possible acids for blocking are monocarboxylic acids such as formic acid, dichloroacetic acid, trifluoroacetic acid or 2-ethylhexanoic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid and hydroxycarboxylic acids such as citric acid or salicylic acid.
  • Complex thermally releasable catalysts are usually adducts of tertiary amines with short-chain diols such as ethylene glycol and carboxylic acid anhydrides such as phthalic anhydride, maleic anhydride or succinic anhydride.
  • Choline and its derivatives are suitable as quaternary ammonium salts which release tertiary amines when exposed to heat.
  • reaction products from cyclic carboxylic acid anhydrides and diamines such as N, N-dimethylethylenediamine can also be used.
  • Typical latent catalysts are, for example, blocked amine and amidine catalysts from Evonik® such as Polycat® SA 1/10, SA 2 LE, SA 4 and SA-8, Dabco® KTM 60, Tosoh® e.g. Toyocat® DB 2, DB 30 , DB 31, DB 40, DB
  • the resin or hardener component of the binder is produced by intensive mixing of the individual components at room temperature and with the exclusion of moisture. The components are obtained with processing-friendly viscosities of 200 to 600 mPas at 20 ° C for the resin component and 200 to 500 mPas at 20 ° C for the hardener component.
  • the resin component of the binder has 50 to 100%, preferably 70 to 90% hydrogen-active compounds and the hardener component of the binder 50 to 100%, preferably 80 to 95% polyisocyanates.
  • the two-component binders described are mixed in combination with refractory and pourable fillers to produce the molding material.
  • These natural and ceramic foundry sands are commonly referred to as basic mold materials. They include quartz sands of various origins and grain shapes, chromite sand, zircon sand, olivine sand, R-sand, magnesia, alkali and alkaline earth halides,
  • Aluminum silicates such as J-sand and Kerphalite®, synthetic sands such as
  • the binder and catalyst content in the molding material can be optimized, taking into account the respective grain spectrum and the specific sand weight, and is preferably between 0.3 and 4.0%, based on the basic molding material, and 0.1 to 2.5% thermally activated Catalyst, based on the resin component, adjusted.
  • the method according to the invention is not restricted to these settings and amounts.
  • the resin and hardener components of the binder can be added in a mixing ratio of 2.5: 1 to 1: 2.5, depending on the respective recipe.
  • Disadvantages of the previous hot box and warm box binder systems, such as formaldehyde and phenol or furfuryl alcohol vapors released during core production or disruptive water released by a condensation reaction, are avoided when using the molding material mixture provided for the process according to the invention.
  • the toxic amine gas used in particular is a considerable procedural disadvantage.
  • the corresponding equipment must be equipped with complex ventilation technology.
  • the amine gas does not react with the molding material and must therefore be continuously removed from the process by an amine scrubber.
  • the present invention does not have these disadvantages. It enables the mold material to harden quickly, for example for core production, without having to use gaseous amines as in the cold box process.
  • the innovative technology of the release of chemically masked catalysts through the introduction of heat is used. This leads to the rapid, thermally induced curing of polyurethane and / or polyurea binders in the molding material and thus enables molded parts to be produced in short cycle times.
  • the binder used in the process according to the invention for the production of molding materials furthermore does not contain any harmful aromatic solvents. Instead, fatty acid esters based on renewable raw materials, synthetic carboxylic acid esters, aliphatic carbonates and / or organic silicon compounds are used, which preferably do not contain any volatile components.
  • the binders and the molding materials themselves have advantageous processing properties such as odorlessness, low vapor pressure, low viscosity, good flowability, adjustable curing speed and high flexural strengths.
  • the ones with the molding materials described The cores and molds produced have a low tendency to defects and good disintegration under casting conditions. During casting, the emissions of volatile organic compounds such as aromatic hydrocarbons and formaldehyde are significantly reduced compared to binders based on phenol-formaldehyde, resin and furan resin.
  • the method according to the invention for processing molding materials makes an important contribution to a low-emission and highly productive foundry.
  • the test conditions are based on the VDG leaflet P71. Quartz sand H31 with 1.6% binder, 0.8% each of which is Flarz and Flärter, and amounts of thermally activated catalysts based on the amount of Flarz, as shown in Table 1, were used to produce molding material mixtures for the binder examples below . These molding material mixtures were stirred in a laboratory mixer for 60 to 120 seconds, then shot with a PLS test body shooting machine at 4 bar shooting pressure into the heatable PBH core box from GF DISA AG and hardened with the introduction of heat through the core box or by introducing heated air. The associated molding material strengths of the test specimens obtained in this way with the dimensions 22.4 x 22.4 x 175 mm were determined as a function of time using the multi-purpose LRu-2e universal strength tester from Multiserw.
  • compositions of the binders used are shown below. All percentages [%] in this document are always to be understood as percentages by weight, unless there is a deviating from this Definition made in the explanatory text.
  • Example 2 Example 3:
  • Table 1 below shows the test results with the exemplary embodiments described and comparative examples V1 and V2 not according to the invention. From the data it can be seen that a thermally activatable catalyst is absolutely necessary in order to achieve short curing times. After the test specimens have cooled down completely (1 hour value), the final strength (24 hour value) is almost reached in most cases. Comparative examples C1 and C2 show that the process according to the invention is not suitable for phenol-formaldehyde resin-based binders. The Pep-Set-Binder V1 requires significantly longer curing times than the variants according to the invention. Comparative binder 2 is a classic cold box binder. The molding materials with the comparative binder 2 are not heat-curable. Presumably, additives in the binder inhibit a reaction of the thermolatent catalyst.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Polyurethanes Or Polyureas (AREA)

Abstract

L'invention concerne un procédé de production de noyaux et de moules en fonte au sable, comprenant au moins les étapes suivantes : A) la fourniture d'un outil de moulage ayant une cavité reproduisant la partie moulée, B) le mélange du matériau de moulage thermodurcissable, le matériau de moulage étant au moins composé des constituants suivants : un liant à deux constituants, exempt de phénol et de formaldéhyde, à base de polyuréthane, contenant un constituant de résine sous forme de mélange d'au moins deux composés qui ont une activité hydrogène par rapport à des isocyanates contenant des groupes hydroxyle et/ou mercapto et/ou amino et/ou carbamide ayant une fonctionnalité OH, SH et NH de 1,5 à 8 et des poids équivalents de 9 à 2 000 g/val des constituants individuels et une fonctionnalité H moyenne de 1,8 à 4,0 et un poids équivalent moyen de 90 à 200 g/val des constituants de résine et un constituant durcisseur contenant un ou plusieurs diisocyanates ou polyisocyanates, un ou plusieurs catalyseurs activables thermiquement ayant des températures d'activation comprises entre 50 et 170 °C et contenant des bases de Brönsted favorisant la réaction de polyuréthane et/ou des acides de Lewis et leurs agents de blocage associés, et un ou plusieurs matériaux de charge coulants résistants au feu, C) l'introduction du matériau de moulage dans l'outil de moulage, D) le durcissement du matériau de moulage thermodurcissable dans l'outil de moulage à l'aide d'un procédé en boîte chaude ou d'un procédé à l'air chaud avec l'outil de moulage chauffant ou l'air chaud à des températures comprises entre 90 et 170 °C, de préférence entre 100 et 130 °C, et E) le retrait de la pièce moulée produite de l'outil de moulage.
EP20771195.3A 2019-08-30 2020-08-27 Procédé de production de noyaux et de moules en fonte au sable Pending EP4021662A1 (fr)

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DE102019123374.7A DE102019123374A1 (de) 2019-08-30 2019-08-30 Verfahren zur Herstellung von Kernen und Formen im Sandformverfahren
PCT/DE2020/100761 WO2021037313A1 (fr) 2019-08-30 2020-08-27 Procédé de production de noyaux et de moules en fonte au sable

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