DE1583531C

DE1583531C - Process for the production of foamed casting molds

Info

Publication number: DE1583531C
Application number: DE19671583531
Authority: DE
Inventors: Manfred Dipl.-Phys. 3201 Barienrode Lottermoser
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-10-14
Filing date: 1967-10-14
Publication date: 1974-03-14

Description

Komponenten derart, daß ein elastischer organischer Schaumkörper entsteht, so können Gießformen mittels unterschnittener Hohlmodelle hergestellt werden. Dabei wird der elastische organische Schaumkörper erst aus dem Hohlmodell entnommen und dann werden die Zeilinnenräume mit anorganischem Material, z. B. durch Tauchen, gefüllt. Diese Möglichkeit stellt eine vorteilhafte Erweiterung der bisher bekannten Formtechniken dar.Components in such a way that an elastic organic foam body is created, so can molds by means of undercut hollow models are produced. The elastic organic foam body is thereby first removed from the hollow model and then the cell interiors are filled with inorganic material, z. B. by diving filled. This possibility represents an advantageous extension of the previously known Forming techniques.

Die Durchführung des Verfahrens geschieht derart, daß flüssige Substanzen, die durch chemische Reaktionen untereinander eine starre oder elastische organische Substanz zu bilden vermögen, wobei ein in Theologischem Sinn harzartiges Stadium durchlaufen wird, vermischt und in den Modellhohlraum eines Hohlmodells (z. B. Kernkasten oder Modell mit Konturenplatte) eingebracht oder auch erst in dem Modellhohlraum vermischt werden. Die genannten chemischen Reaktionen können dabei, falls sie nicht spontan einsetzen, während des Vermischens oder nach dem Vermischen katalytisch, elektrolytisch, thermisch angeregt oder durch andere geeignete, dem Fachmann geläufige Maßnahmen in Gang gesetzt werden. Kurz vor oder unmittelbar nach dem Einsetzen der Reaktion wird durch an sich bekannte Maßnahmen ein Aufschäumen des Gemisches eingeleitet, beispielsweise über eine Decarboxylierungsreaktion. Die Durchlöcherung der Schaumzellwände kann dabei in bekannter Weise durch oberflächenaktive Zusätze bewirkt werden. Die Reaktionsgeschwindigkeit wird so eingestellt, daß die Reaktionstemperatur ein für das jeweilige Modellmaterial zuträgliches Maß nicht übersteigt. Nach Beendigung der Reaktion ist ein den Modellhohlraum konturengetreu wiedergebender starrer oder elastischer Schaumkörper vorhanden. Die Schaumzellen werden jetzt mit gelösten oder/und suspendierten anorganischen Substanzen gefüllt. Dieses Füllen wird durch die Durchlöcherung der Zellwände ermöglicht. Ohne Einschränkung des Erfindungsgedankens kann die Lösung bzw. Suspension mittels geeigneter Düsen durch die Einfüllöffnungen des Hohlmodells gedrückt werden, während sich der Schaumkörper noch im Hohlmodell befindet. Indem nacheinander zwei verschiedene Lösungen durch den Schaumkörper hindurchgedrückt werden, kann auch feste anorganische Substanz in den Zellhohlräumen ausgefüllt werden. Danach kann überschüssige Feuchtigkeit mit durchgedrückter Luft entfernt werden. Am einfachsten wird überschüssige Feuchtigkeit durch Lagern entfernt. Schrumpfeffekte der anorganischen Substanz werden zur Regulierung der Gasdurchlässigkeit ausgenutzt.The process is carried out in such a way that liquid substances are produced by chemical reactions are able to form a rigid or elastic organic substance with one another, with an in Theological sense resin-like stage is passed through, mixed and in the model cavity of a Hollow model (e.g. core box or model with contour plate) introduced or only in the Model cavity are mixed. The chemical reactions mentioned can happen if they don't start spontaneously, during the mixing or after the mixing catalytic, electrolytic, thermally excited or set in motion by other suitable measures familiar to the person skilled in the art will. Shortly before or immediately after the onset of the reaction, measures known per se are used a foaming of the mixture is initiated, for example via a decarboxylation reaction. The perforation of the foam cell walls can be done in a known manner by surface-active additives be effected. The reaction rate is adjusted so that the reaction temperature does not exceed the acceptable level for the respective model material. After the reaction is complete a rigid or elastic foam body that faithfully reproduces the contour of the model cavity is present. The foam cells are now filled with dissolved and / or suspended inorganic substances filled. This filling is made possible by the perforation of the cell walls. Without limitation of the According to the invention, the solution or suspension can be fed through the filling openings by means of suitable nozzles of the hollow model are pressed while the foam body is still in the hollow model. By doing successively two different solutions can be pressed through the foam body solid inorganic substance can also be filled in the cell cavities. After that, excess can Moisture can be removed with forced air. The easiest way is excess moisture removed by storage. Shrinkage effects of the inorganic substance are used to regulate the Gas permeability exploited.

Eine besondere Durchführungsform des Verfahrens besteht in einer Vergrößerung der Zellwand-Löcher derart, daß die Durchmesser dieser Löcher größenordnungsmäßig den Durchmessern der Zellen nahekommen. Der organische Schaumkörper besitzt dann keine Zellstruktur mehr, sondern die Struktur eines dreidimensionalen Netzes. Dieses dreidimensionale Netz aus organischer Substanz wird in anorganische Substanz eingebettet, die sich infolge nachträglicher Schrumpfung von den Fäden des organischen Netzes löst. Diese Schrumpfung läßt sich soweit treiben, insbesondere bei Verwendung großmoleküliger oder polymerer anorganischer Substanzen, daß die anorganische Substanz ebenfalls die Struktur eines dreidimensionalen Netzes annimmt. Der fertige Formkörper besteht dann aus zwei miteinander verketteten dreidimensionalen Netzen, einem organischen und einem anorganischen Netz.
Gießformen aus miteinander verketteten dreidimensionalen Netzen verbinden extrem hohe Gasdurchlässigkeit mit gleichzeitiger Schutzgaswirkung infolge thermischer Zersetzung eines der Netze. Sie besitzen Bedeutung für das Vergießen von Metallen, die zu Reaktionen mit der Atmosphäre neigen. Gutes Zerfallsvermögen und hohe Wärmeschockbeständigkeit sind zusätzliche Vorteile.
Durchführungsbeispiele:A special embodiment of the method consists in enlarging the cell wall holes in such a way that the diameters of these holes are of the order of magnitude of the diameters of the cells. The organic foam body then no longer has a cell structure, but the structure of a three-dimensional network. This three-dimensional network of organic matter is embedded in an inorganic substance which, as a result of subsequent shrinkage, becomes detached from the threads of the organic network. This shrinkage can be driven to such an extent, especially when using large-molecule or polymeric inorganic substances, that the inorganic substance also assumes the structure of a three-dimensional network. The finished molded body then consists of two interlinked three-dimensional networks, an organic and an inorganic network.
Casting molds made of interlinked three-dimensional networks combine extremely high gas permeability with a simultaneous protective gas effect due to thermal decomposition of one of the networks. They are important for the casting of metals that tend to react with the atmosphere. Good disintegrability and high thermal shock resistance are additional advantages.
Implementation examples:

example 1

In einem aus gefülltem Epoxidharz bestehenden, mit Einfüllöffnungen und Entlüftungsdüsen versehenen Hohlmodell wird in an sich bekannter Weise ein Polyurethanschaumkörper erzeugt, dessen Zellwände durchlöchert sind. Als Trennmittel dient Hartparaffin. Dieser Schaumkörper wird mit wässerigem Tonschlicker vollgepreßt, aus dem Hohlmodell entnommen und in einem Kern trockenofen bei 120 bis 150° C nachbehandelt.In a filled epoxy resin with filling openings and ventilation nozzles Hollow model, a polyurethane foam body is produced in a manner known per se, the cell walls of which are perforated. Hard paraffin serves as a release agent. This foam body is made with aqueous clay slip fully pressed, removed from the hollow model and in a core drying oven at 120 to 150 ° C post-treated.

Example 2

Der Polyurethanschaumkörper wird mit Wasserglaslösung vollgepreßt, es wird n/lOO-Salzsäure nachgedrückt und wie im Beispiel 1 nachbehandelt.The polyurethane foam body is pressed full of water glass solution, n / 100 hydrochloric acid is injected and aftertreated as in Example 1.

Example 3

Ein aus unterschrittenem Hohlmodell erhaltener elastischer Polyurethanschaumkörper mit durchlöcherten Zellwänden wird in eine gasdichte Stahlbüchse gebracht, in die man nach erfolgter Evakuierung wässerigen Tonschlicker einströmen läßt. Der Formkörper wird mit Wasser abgespült und wie im Beispiel 1 nachbehandelt.An elastic polyurethane foam body with perforated Cell walls are placed in a gas-tight steel can, into which one is after evacuation watery clay slip can flow in. The shaped body is rinsed with water and as in Example 1 aftertreated.

Claims

1 2 and thus binds the grains. The foam cells located between the patent claims: grains result in a saving of binder compared to the conventional ones

1. Process for the production of casting molds, processes in which compact binder in the which is made of organic material with a foam structure 5 grain spaces. On the other hand, on the one hand and inorganic material, but the foam cells make it easier for the liquid to penetrate consist of marked metal in the gap between the grains, so that the net that initially a cast made of organic material is compared by means of compact binders existing castings that are made true to the contour of the model cavity are coarser and less contoured reproducing foam body with perforated to fail.

th cell walls is produced, the cell interior of which The new process is said to address the disadvantages and space then filled with inorganic material remove the limitations of the known methods will. and also the production of large quantities in

2. The method according to claim 1, characterized in rapid succession using models that are not heat-resistant, allow the diameter of the holes 15 to be dig. According to the invention In the cell walls of the organic foam body, this goal is achieved by a process for according to the order of magnitude of the cell diameter sem is adjusted so that the structure of the material with foam structure on the one hand and inorganic organic Foam bodies that are made of a three-dimensional material on the other hand, thereby gesionalen Network is. . 20 indicates that initially an organic material

3. The method according to claims 1 to 2, characterized in material existing, the model cavity contoured, that the casting molds by means of faithfully reproducing foam bodies with undercut Hollow models are made, perforated cell walls are made, the cells of which the organic foam body is then filled with inorganic material in the interior spaces is made elastic in a known manner and 25 are.

The method according to the invention differs only after it has been removed from the hollow model

the filling of the cell interiors with inorganic is derived from the method of the German patent specification

Material is made. 1 255 239 not only in the working method, but

also clearly in the result of the respective

30 gen working method. According to the procedure of

German Patent 1,255,239

The invention relates to a method of manufacturing consists of an-

development of foamed casting molds with perforated organic grains, which are found in most cases

ten cell walls, especially for metal foundries, do not touch each other. The way between

and aims to produce both the molds and the grains that exist and only with empty ones

also to improve their usability. Interspaces filled with foam cells favor

Process for the production of casting molds or for the above-mentioned penetration of liquid metal

Casting models using materials with In addition, the flowability of a mixture is based on:

Foam structure and perforated cell walls are foam and sand, as it is after 'the method de.

known. In "Gießeren" 46 (1959) page 764 40 German patent specification 1255 239 is used

Casting molds made of inorganic substance with porous that of a viscous pulp, so that even from these

Foam structure described. These have every basic shape with fine contours or shapes for

the disadvantage of insufficient gas permeability, because precise castings cannot be made. To the

the metal must be filled in by means of compressed air.

and only part of the air of the mold cavity is made from the mold using inorganic 45 process

pressed through the pores of the mold, like substance-filled foam cells. Because the inside of the cells

rend another part enclosed in the casting spaces of a foam have more volume al

will. A pressure-resistant assembly is also composed of its cell walls, which is the volume fraction of the anorga

Molds for more complex or undercut niches of substance in the total volume of the material

pieces hardly feasible. Also from 50 of the finished form here larger than with a Forr

inorganic substance with a porous foam structure according to German patent specification 1 255 239. Feme

exist in the German Auslegeschrift the inorganic particles have a fiction

1 081 602 described casting models. With this form, no distances from each other, because si

If the pores are subsequently formed with plastic, an initially liquid, later rigid body

fills to create abrasion-resistant surfaces and edges, so that the material can be used in the finished form

keep. Because of the resulting total gas-dependent filling. These circumstances work together

metal penetration prepared in this way can be used to counteract impermeability. It is also flowable

Do not use models as molds at all. the ability of a liquid foam to be obviously better a

Organic substance with a foam structure on the one hand that of a foam-sand mixture, so that from de?

and 60 foam parts containing inorganic substance, on the other hand, are made with extremely fine contours;

Casting molds will be able to be interpreted according to the method of. This is known by d

see patent specification 1 255 239 produced. Process expansion of a nascent show

according to granular inorganic molding material, is effectively supported and in the technology d

especially sand, with a foaming polyurethane foams for the production of more precise fei.

capable organic binder mixed. Already used in the 65-pore foam body.

In the course of the mold production, the binder in The Schaur made of organic material

transferred to the foam state. In this state the body can get both rigid and elastic

In the finished form, it fills the gaps between the grains. If you choose the reacting with each other