EP0629458A1 - Embedding material for casting - Google Patents

Embedding material for casting Download PDF

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Publication number
EP0629458A1
EP0629458A1 EP94108194A EP94108194A EP0629458A1 EP 0629458 A1 EP0629458 A1 EP 0629458A1 EP 94108194 A EP94108194 A EP 94108194A EP 94108194 A EP94108194 A EP 94108194A EP 0629458 A1 EP0629458 A1 EP 0629458A1
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Prior art keywords
investment
zeolite
zeolites
cast
materials according
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EP94108194A
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German (de)
French (fr)
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EP0629458B1 (en
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Peter Dr. Schwabe
Martin Dr. Grunwald
Lothar Dr. Puppe
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Kulzer GmbH
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Bayer AG
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    • 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

Definitions

  • the present invention relates to investment materials containing zeolites and to models and molds made therefrom.
  • the investment materials according to the invention are used in metal casting, preferably in the production of precision castings.
  • the object of the present invention was to produce cast investment materials which are free from efflorescence, but which still have good mechanical properties.
  • this object is achieved by adding zeolites to investment compositions known per se.
  • the investment materials according to the invention are generally used in metal casting, for example in the restoration and copying of valuable metal objects.
  • a preferred area of application for the investment materials according to the invention is dental technology, where tooth replacement parts are produced with the aid of cast investment materials. Wax models that reflect the shape of the tooth restoration to be cast are embedded with the aid of such a mass, or investment models, such as in the production of model cast frameworks for partial dentures, are produced. The wax models are heated together with the investment material and burn off without residue. This creates cavities that are poured out with the dental restoration materials used, usually metal alloys.
  • the investment compositions are known per se. They usually consist of a powder composed of refractory materials such as quartz or cristobalite and binders such as magnesium oxide / ammonium phosphate or calcium sulfate hemihydrate, and a mixing liquid such as water or a silica sol solution. So-called phosphate-bonded investment materials are frequently used, which essentially contain magnesium oxide and phosphates as binders and quartz and cristobalite as refractory materials. A silica sol solution is often used as the mixing liquid.
  • Duplicating materials include aqueous agar-agar compositions or also the increasingly used, very accurate and true-to-shape silicone duplicating materials.
  • the efflorescence mentioned above precipitates of crystalline alkali metal phosphates, often occurs on the surface of the investment model.
  • the alkalis presumably come mainly from the additives that are added to stabilize the silica sols used as mixing liquids, or they come from alkali phosphate additives that are added to the investment powder formulations to control the setting kinetics.
  • EP-0 417 527 Another attempt to suppress the "efflorescence" is described in EP-0 417 527. There the addition of 0.01 to 10% by weight of at least one in Water and / or alcohol-soluble, solid organic acid with 2 to 10 carbon atoms is recommended for the production of molds from casting investment materials.
  • the zeolites are preferably used in amounts of 0.1 to 10.0% by weight (based on the total powdery mass before adding the mixing liquid), particularly preferably in amounts of 0.4 to 5.0% by weight.
  • the individual zeolite structures differ in the arrangement and size of the channels and cavities and in their composition. Interchangeable cations are stored to compensate for the negative charge of the lattice, which is caused by the proportion of M2.
  • the adsorbed water phase qH2O is reversibly removable without the structure losing its structure.
  • M2 is often aluminum, but can be partially or completely substituted by other trivalent elements.
  • zeolites A detailed description of zeolites can be found, for example, in the monograph by D.W. Breck "Zeolite Molecular Sieves, Structure, Chemistry and Use", J. Wiley & Sons, New York, 1974.
  • zeolites are particularly suitable: faujasite, mordenite, zeolite A, zeolite ⁇ , zeolite ⁇ , zeolite L, offretite, ZSM 12, pentasile, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, zeolite T, chabasite, Gmelinite, Ferrierite, Zeolite Rho, ZK-5 and others
  • the zeolites suitable for the process according to the invention can contain alkali cations such as Li, Na, K, Rb or alkaline earth cations such as Mg Ca, Sr or other cations such as H, NH4, Zn, Cu, Ni, Co, Mn, rare earth metals, among others. Mixed forms can also be used.
  • alkali cations such as Li, Na, K, Rb or alkaline earth cations such as Mg Ca, Sr or other cations such as H, NH4, Zn, Cu, Ni, Co, Mn, rare earth metals, among others.
  • alkali cations such as Li, Na, K, Rb or alkaline earth cations such as Mg Ca, Sr or other cations such as H, NH4, Zn, Cu, Ni, Co, Mn, rare earth metals, among others.
  • Mixed forms can also be used.
  • Zeolites with many acidic centers are particularly preferred for the process according to the invention, as arise, for example, from the treatment of zeolites with a faujasite structure with ammonium salt solutions or rare earth salt solutions and subsequent thermal treatment.
  • the amount of the zeolites described above is preferably from 0.1 to 10% by weight.
  • the efflorescence-preventing effect of different types of zeolite is different. Simple experiments enable optimal dosing.
  • the alkali, alkaline earth or rare earth-containing zeolites are very effective.
  • the most effective zeolites are those of the H type Y zeolite.
  • H-zeolite Y For H-zeolite Y, about 0.3 to 1.5% by weight was found as a particularly preferred amount for achieving the efflorescence-preventing effect; for the zeolites containing rare earths, the particularly preferred addition amount is 0.7 to 2.0% by weight. %.
  • the basic formulations of the investment powders according to the invention are in a conventional manner known per se in a suitable mixing unit, for example in a Nauta mixer, Lödige mixer or the like. can be produced by mixing the powdered additives including the zeolites together. However, it is also possible to prepare premixes containing the zeolite and to mix these premixes. In addition, it is also possible with the described zeolite-containing investment formulations according to the invention to spray them with isoparaffins in a manner known per se without loss of the desired properties described above, for example to improve their flow behavior again.
  • the investment powder mixtures according to the invention containing zeolite show no disadvantages compared to investment mixtures which do not contain zeolite. There are no processing-related changes in the setting time and setting temperature. The gel tolerance is still good. The mechanical strength of the casting muffle or of the model made from the investment material remains good, the same applies to the setting expansion, an important parameter for the degree of dimensional accuracy of the casting subsequently obtained.
  • the investment formulations according to the invention can be used in particular both with respect to duplicating silicone and with respect to agar-agar duplicating material.
  • the setting expansion, processing time and compressive strength are determined in accordance with DIN 13919, Part 2, June 1984.
  • the setting time is the point in time at which the setting temperature reaches the maximum temperature.
  • the tendency to efflorescence was tested by mixing the investment powder described with a commercially available silica sol mixing liquid (Levotherm mixing liquid) and pouring the mixed casting investment paste into an addition-crosslinked silicone duplicating molding compound (for example from Tecnovil commercial goods), by means of the solidified investment mold and the demoulding mold after removal from the mold and standing in the air is examined.
  • the investment powder composition is produced by homogeneously mixing the individual components in a throwing vane mixer (Lödige mixer), conical truncated cone mixer with rotating screw (Nauta mixer) or in tumble mixers, but in principle other suitable mixing units can also be used.
  • a throwing vane mixer Liödige mixer
  • Conical truncated cone mixer with rotating screw Naauta mixer
  • tumble mixers but in principle other suitable mixing units can also be used.
  • suitable mixing units can also be used.
  • the examples listed below are intended to describe the invention without restricting it by the illustration of these examples.
  • phosphate-bound casting investment materials are e.g. B. in K. Eichner, Dental materials and their processing, Vol. 1, Wegig Verlag, Heidelberg, 1981, p. 42; or z. B. in: Quintessenz Zahntechnik 17, 73-86 (1991).
  • the quartz powder used in the examples has an SiO2 content> 99% with a total residue of approx. 90 vol.% With a grain diameter of 2 ⁇ m measured using a Cilas granulometer and a total residue of approx. 89 wt Sink velocity equivalent diameter of 2.5 ⁇ m, measured according to sedimentation analysis using Sedi Graph 5100.
  • a type of quartz sand that can be used has an SiO2 content of> 99% with an average grain size of 0.28 mm.
  • a usable cristobalite flour type with a SiO2 content of> 99% shows a grain size distribution according to sieve analysis of (diameter / weight% fraction)> 200 ⁇ m / 0.5,>100/5,>63/20,> 40/44, ⁇ 40 / 30.5 with a BET surface area of 0.9 m2 / g.
  • Fabutit 746 (from Budenheim) are used as phosphates in addition to a little Fabutit GI / 66A (from Budenheim), and magnesium oxide Dynamag K (from Hüls) in addition to a little Mag Chem 40 (Göbel & Pfrengle).
  • a red dye (Conrads) was used to color the mass, which generally has the following composition: 53.9-51.6% SiO2; 24.0-27.4% Al2O3; 6.3-11.6% Fe2O3; 0.8-0.21% MgO, loss on ignition 12.5-8.5%.
  • zeolite according to the invention has no negative influence on the compatibility with duplicating gel and the expansion of the setting.
  • the development of mechanical strength through the addition of zeolite is positive.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Dental Preparations (AREA)
  • Mold Materials And Core Materials (AREA)
  • Adornments (AREA)
  • Dental Prosthetics (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Abstract

The present invention relates to embedding materials containing zeolites and to patterns and moulds produced from these materials. The embedding materials according to the invention are used in metal casting, preferably in the production of precision castings.

Description

Die vorliegende Erfindung betrifft Zeolithe enthaltende Einbettmassen sowie daraus gefertigte Modelle und Formen. Die erfindungsgemäßen Einbettmassen werden beim Metallguß eingesetzt, vorzugsweise bei der Herstellung von Präzisionsgußteilen.The present invention relates to investment materials containing zeolites and to models and molds made therefrom. The investment materials according to the invention are used in metal casting, preferably in the production of precision castings.

Bei der Herstellung von Metallgußteilen kommt es in vielen Fällen auf eine möglichst identische Wiedergabe von Details wie feinen Oberflächenstrukturen an. Hierbei wird insbesondere in Fällen, in denen das Original nicht beliebig lange zur Verfügung steht, von diesem zunächst eine Abformung, zum Beispiel aus Silicon, angefertigt, mit deren Hilfe ein sogenanntes Meistermodell, beispielsweise aus Gips, hergestellt wird.In the production of metal castings, the most important thing is to reproduce details such as fine surface structures as identically as possible. In this case, especially in cases where the original is not available for any length of time, an impression is made of it, for example made of silicone, with the aid of which a so-called master model, for example made of plaster, is produced.

Von diesem wird erneut eine Abformung, meist aus Agar-Agar oder Silicon, hergestellt, mit deren Hilfe man eine Kopie des Meistermodells aus Gips, oder, wenn exakt auf das Original passende Teile angefertigt werden sollen, aus Einbettmasse herstellt.From this, an impression is again made, usually made of agar-agar or silicone, with the help of which a copy of the master model is made of plaster or, if parts are to be made exactly to the original, of investment material.

Im letzten Fall kommt es insbesondere gegenüber den hydrophoben Siliconoberflächen zur Bildung von feinen, salzartigen Krusten auf der Oberfläche des aus Einbettmasse gefertigten Modells, den sogenannten Ausblühungen. Der Versuch, diese z.B. mechanisch zu entfernen, führt häufig zu Beschädigungen, die wie die nicht entfernten Ausblühungen selbst die Ursache von Fehlern an dem später hergestellten Gußobjekt sind.In the latter case, especially in relation to the hydrophobic silicone surfaces, fine, salt-like crusts form on the surface of the model made of investment material, the so-called efflorescence. Attempting to remove them mechanically, for example, often leads to damage which, like the efflorescence that has not been removed, is itself the cause of defects in the cast object to be produced later.

Der vorliegenden Erfindung lag die Aufgabe zugrunde, Gußeinbettmassen herzustellen, die frei von Ausblühungen sind, jedoch über unverändert gute mechanische Eigenschaften verfügen.The object of the present invention was to produce cast investment materials which are free from efflorescence, but which still have good mechanical properties.

Erfindungsgemäß wird diese Aufgabe durch Zusatz von Zeolithen zu an sich bekannten Einbettmassezusammensetzungen gelöst. Die erfindungsgemäßen Einbettmassen werden beim Metallguß im allgemeinen eingesetzt, zum Beipsiel bei der Restauration und Kopie wertvoller Metallobjekte. Ein bevorzugtes Anwendungsgebiet für die erfindungsgemäßen Einbettmassen ist die Dentaltechnik, wo mit Hilfe von Gußeinbettmassen Zahnersatzteile hergestellt werden. Dabei werden Wachsmodellationen, die die Form der zu gießenden Zahnrestauration wiedergeben, mit Hilfe einer solchen Masse eingebettet, oder aber es werden Einbettmassemodelle, wie z.B. bei der Herstellung von Modellgußgerüsten für partielle Zahnprothesen, hergestellt. Die Wachsmodellationen werden gemeinsam mit den Einbettmassen erwärmt und verbrennen dabei rückstandslos. Dadurch entstehen Hohlräume, die mit den verwendeten dentalen Restaurationsmaterialien, in der Regel Metallegierungen, ausgegossen werden. Nach dem Erhärten und Abkühlen der Restaurationsmaterialien werden die Einbettmassen entfernt und das gegossene Zahnersatzteil liegt vor, welches nach weiteren Arbeitsschritten, wie Abstrahlen, Polieren, Verblenden etc. für die Eingliederung in das Gebiß zur Verfügung steht. Die Einbettmassezusammensetzungen sind an sich bekannt. Sie bestehen in der Regel aus einem Pulver, welches aus feuerfesten Materialien, wie z.B. Quarz oder Cristobalit, und Bindemittel, wie z.B. Magnesiumoxid/Ammoniumphosphat oder Calciumsulfathalbhydrat, zusammengesetzt ist, und einer Anmischflüssigkeit, wie z.B. Wasser oder eine Kieselsollösung. Häufig werden sogenannte phosphatgebundene Einbettmassen verwendet, die im wesentlichen als Bindemittel Magnesiumoxid und Phosphate sowie als feuerfeste Materialien Quarz und Cristobalit enthalten. Als Anmischflüssigkeit wird häufig dafür eine Kieselsollösung verwendet. Die Reaktionen bei der Verfestigung und beim Erhitzen der angemischten Einbettmasse lassen sich durch die folgenden Reaktionsgleichungen darstellen:
Verfestigung:



        NH₄H₂PO₄ + MgO → MgNH₄PO₄ + H₂O



Erhitzen:



        2 MgNH₄PO₄ → Mg₂P₂O₇ + H₂O + 2 NH₃



Bei verschiedenen Arbeitstechniken, wie z.B. bei der Herstellung von Einbettmassemodellen für die Anfertigung von Modellgußgerüsten oder bei der Herstellung von feuerfesten Einzelstümpfen, werden bisweilen Abformungen von zahntechnischen Modellen, die häufig aus Gips als Modellmaterial bestehen, angefertigt, und diese dann mit den zuvor beschriebenen Einbettmassen gefüllt, wobei die Einbettmasse sich in dieser Abformmasse verfestigt. Dieses Verfahren ist auch unter der Bezeichnung "Dublieren" bekannt. Als Dubliermaterialien sind u.a. wässrige Agar-Agar-Massen oder aber auch die zunehmend eingesetzten, sehr wiedergabegenauen und formtreuen Silicondubliermateiralien bekannt. Bei der Verfestigungsreaktion kommt es nach deren Abschluß und dem Entformen des so erhaltenen Einbettmassemodells aus der Silicondublierabformmasse häufig zu den bereits oben erwähnten Ausblühungen, Ausscheidungen von kristallinen Alkaliphosphaten, auf der Oberfläche der Einbettmassemodelle.According to the invention, this object is achieved by adding zeolites to investment compositions known per se. The investment materials according to the invention are generally used in metal casting, for example in the restoration and copying of valuable metal objects. A preferred area of application for the investment materials according to the invention is dental technology, where tooth replacement parts are produced with the aid of cast investment materials. Wax models that reflect the shape of the tooth restoration to be cast are embedded with the aid of such a mass, or investment models, such as in the production of model cast frameworks for partial dentures, are produced. The wax models are heated together with the investment material and burn off without residue. This creates cavities that are poured out with the dental restoration materials used, usually metal alloys. After the hardening and cooling of the restoration materials, the investment material is removed and the cast dental prosthesis is available, which is available for incorporation into the dentition after further work steps, such as blasting, polishing, blending, etc. The investment compositions are known per se. They usually consist of a powder composed of refractory materials such as quartz or cristobalite and binders such as magnesium oxide / ammonium phosphate or calcium sulfate hemihydrate, and a mixing liquid such as water or a silica sol solution. So-called phosphate-bonded investment materials are frequently used, which essentially contain magnesium oxide and phosphates as binders and quartz and cristobalite as refractory materials. A silica sol solution is often used as the mixing liquid. The reactions during solidification and when heating the mixed investment can be represented by the following reaction equations:
Consolidation:



NH₄H₂PO₄ + MgO → MgNH₄PO₄ + H₂O



Heat:



2 MgNH₄PO₄ → Mg₂P₂O₇ + H₂O + 2 NH₃



With various working techniques, such as the production of investment material models for the fabrication of model cast frameworks or the production of fireproof individual dies, impressions of dental technology models, which often consist of plaster as model material, are sometimes made and these are then filled with the investment materials described above , whereby the investment solidifies in this impression material. This process is also known as "duplication". Duplicating materials include aqueous agar-agar compositions or also the increasingly used, very accurate and true-to-shape silicone duplicating materials. In the solidification reaction, after the completion and the demolding of the investment model thus obtained from the silicone duplicating impression material, the efflorescence mentioned above, precipitates of crystalline alkali metal phosphates, often occurs on the surface of the investment model.

Die Alkalien entstammen vermutlich hauptsächlich aus den Zusätzen, die zur Stabilisierung den als Anmischflüssigkeiten verwendeten Kieselsollösungen zugegeben werden, oder aber sie entstammen aus Alkaliphosphatzusätzen, die den Einbettmassepulverrezepturen zur Steuerung der Abbindekinetik zugesetzt werden.The alkalis presumably come mainly from the additives that are added to stabilize the silica sols used as mixing liquids, or they come from alkali phosphate additives that are added to the investment powder formulations to control the setting kinetics.

Diese sogenannten "Ausblühungen" können die Paßgenauigkeit der auf Grundlage solcher Einbettmassemodelle hergestellten Zahnersatzteile negativ beeinflussen, so daß eine Vermeidung der "Ausblühungen" notwendig ist.These so-called "efflorescence" can have a negative influence on the accuracy of fit of the dental prosthesis parts produced on the basis of such investment material models, so that avoidance of the "efflorescence" is necessary.

Es hat nicht an Versuchen gefehlt, diese Ausblühungen zu verhindern. Es ist bekannt, daß Einbettmasserezepturen mit deutlich veränderter Abbindekinetik und geringerer Abbindetemperatur in dieser Hinsicht verbessert wurden; diese Massen sind jedoch gegenüber Dubliergel auf Agar-Agar-Basis nicht verwendbar, da es bei den niedrigen Abbindetemperaturen gegenüber den Agar-Agar-Dubliermaterialien zu Anhaftungen von Einbettmasse kommt. Dies bedeutet, daß diese Einbettmasserezepturen dann nicht mehr universell für Silicon- und Agar-Agar-Dubliermaterialien angewendet werden können, was die Verwendbarkeit stark einschränkt.There has been no shortage of attempts to prevent this efflorescence. It is known that investment formulations with significantly changed setting kinetics and lower setting temperature have been improved in this regard; however, these compositions cannot be used in relation to agar-agar-based duplicating gel, since the low setting temperatures compared to the agar-agar duplicating materials lead to the adhesion of investment material. This means that these investment compound formulations can then no longer be used universally for silicone and agar-agar duplicating materials, which severely limits their usability.

Einen anderen Versuch, die "Ausblühungen" zu unterdrücken, beschreibt die EP-0 417 527. Dort wird der Zusatz von 0,01 bis 10 Gew.-% mindestens einer in Wasser und/oder Alkohol löslichen, festen organischen Säure mit 2 bis 10 C-Atomen bei der Herstellung von Gußformen aus Gußeinbettmassen empfohlen.Another attempt to suppress the "efflorescence" is described in EP-0 417 527. There the addition of 0.01 to 10% by weight of at least one in Water and / or alcohol-soluble, solid organic acid with 2 to 10 carbon atoms is recommended for the production of molds from casting investment materials.

Diese bei den üblichen Vorwärmtemperaturen verbrennbaren organischen Verbindungen können zu einer Schwächung des keramischen Gefüges führen sowie eine Erhöhung der die Paßgenauigkeit der fertigen Arbeit negativ beeinflußenden Abbindeexpansion bewirken. Zugabemengen in der Größenordnung von 1,2 Gew.-% bewirken bereits eine signifikante Senkung der Abbindetemperatur und deutliche Steigerung der Abbindezeit, die eine universelle Anwendung für Silicon- und Agar-Agar-Gel-Dubliermaterialien verhindern.These organic compounds which are combustible at the usual preheating temperatures can lead to a weakening of the ceramic structure and an increase in the setting expansion which negatively affects the accuracy of fit of the finished work. Additions of the order of 1.2% by weight already bring about a significant reduction in the setting temperature and a significant increase in the setting time, which prevent universal use for silicone and agar-agar gel duplicating materials.

Eine Zugabe von 5,0 Massen-% Citronensäure zu einer Einbettmasse bestehend aus 42,0 Gew.-% Quarzsand; 25,0 Gew.-% Cristobalitmehle; 9,1 Gew.-% Magnesiumoxid; 8,0 Gew.-% Phosphate; 0,5 Gew.% Farbstoffpigmente und 10,4 Gew.-% Quarzmehl führt zu einer Masse, die mit einer Anmischflüssigkeitsmenge von 17 ml Kieselsollösung auf 100 g Pulver zu keiner verarbeitbaren Konsistenz aufgrund einer extrem langsamen Erhärtungsreaktion und einer sehr ungleichmäßigen Erhärtung führt.An addition of 5.0% by mass of citric acid to an investment consisting of 42.0% by weight of quartz sand; 25.0% by weight cristobalite flours; 9.1% by weight magnesium oxide; 8.0% by weight phosphates; 0.5% by weight of pigment pigments and 10.4% by weight of quartz powder leads to a mass which, with a mixing liquid amount of 17 ml of silica sol solution per 100 g of powder, does not lead to a processable consistency due to an extremely slow hardening reaction and a very uneven hardening.

Es wurde gefunden, daß die der Erfindung zugrundliegende Aufgabe durch den Zusatz von Zeolithen zu den an sich bekannten Einbettmassen gelöst wird.It has been found that the object on which the invention is based is achieved by adding zeolites to the investment materials known per se.

Die Zeolithe werden bevorzugt in Mengen von 0,1 bis 10,0 Gew.-%, (bezogen auf die pulverförmige Gesamtmasse vor dem Zusatz der Anmischflüssigkeit) eingesetzt, besonders bevorzugt in Mengen von 0,4 bis 5,0 Gew.-%.The zeolites are preferably used in amounts of 0.1 to 10.0% by weight (based on the total powdery mass before adding the mixing liquid), particularly preferably in amounts of 0.4 to 5.0% by weight.

Erfindungsgemäß bevorzugt einzusetzende Zeolithe sind durch die allgemeinen Formel (I) charakterisiert:



        M¹n[mM²O₂ x n SiO₂] x qH₂O



Hierin bedeuten:

M¹
ein Äquivalent eines austauschbaren Kations, dessen Anzahl dem Anteil von M² entspricht;
M²
ein dreiwertiges Element, welches gemeinsam mit dem Si das oxidische Gerüst des Zeoliths bildet;
n/m
das SiO₂/M²O₂-Verhältnis;
q
die Menge des adsorbierten Wassers
Zeolithe sind von ihrer Grundstruktur her kristalline Alumosilikate, die aus einem Netzwerk von SiO₄- bzw. M²O₄-Tetradern aufgebaut sind. Die einzelnen Tetraedern sind mit Sauerstoffbrücken über die Ecken der Tetraeder untereinander verknüpft und bilden ein räumliches Netzwerk, das gleichmäßig von Kanälen und Hohlräumen durchzogen ist.Zeolites to be preferably used according to the invention are characterized by the general formula (I):



M¹n [mM²O₂ xn SiO₂] x qH₂O



Here mean:
M¹
an equivalent of a replaceable cation, the number of which corresponds to the proportion of M²;
M²
a trivalent element, which together with the Si forms the oxidic framework of the zeolite;
n / m
the SiO₂ / M²O₂ ratio;
q
the amount of water adsorbed
The basic structure of zeolites is crystalline aluminosilicates, which are made up of a network of SiO₄ and M²O₄ tetraders. The individual tetrahedra are linked with each other with oxygen bridges across the corners of the tetrahedra and form a spatial network that is evenly interspersed with channels and cavities.

Die einzelnen Zeolithstrukturen unterscheiden sich durch die Anordnung und Größe der Kanäle und Hohlräume sowie durch ihre Zusammensetzung. Als Ausgleich für die negative Ladung des Gitters, die durch den Anteil an M² zustande kommt, sind austauschbare Kationen eingelagert. Die adsorbierte Wasserphase qH₂O ist reversibel entfernbar, ohne daß das Gerüst seine Struktur verliert.The individual zeolite structures differ in the arrangement and size of the channels and cavities and in their composition. Interchangeable cations are stored to compensate for the negative charge of the lattice, which is caused by the proportion of M². The adsorbed water phase qH₂O is reversibly removable without the structure losing its structure.

M² ist vielfach Aluminium, kann aber durch andere dreiwertige Elemente teilweise oder ganz substituiert sein.M² is often aluminum, but can be partially or completely substituted by other trivalent elements.

Eine ausführliche Darstellung von Zeolithen ist beispielsweise in der Monographie von D.W. Breck "Zeolite Molecular Sieves, Structure, Chemistry and Use", J. Wiley & Sons, New York, 1974, gegeben.A detailed description of zeolites can be found, for example, in the monograph by D.W. Breck "Zeolite Molecular Sieves, Structure, Chemistry and Use", J. Wiley & Sons, New York, 1974.

Für das erfindungsgemäße Verfahren sind z.B. folgende Zeolithe besonders geeignet: Faujasite, Mordenite, Zeolith A, Zeolith β, Zeolith Ω, Zeolith L, Offretit, ZSM 12, Pentasile, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, Zeolith T, Chabasite, Gmelinite, Ferrierite, Zeolith Rho, ZK-5 u.a.For the method according to the invention e.g. the following zeolites are particularly suitable: faujasite, mordenite, zeolite A, zeolite β, zeolite Ω, zeolite L, offretite, ZSM 12, pentasile, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, zeolite T, chabasite, Gmelinite, Ferrierite, Zeolite Rho, ZK-5 and others

Die für das erfindungsgemäße Verfahren geeigneten Zeolithe können Alkalikationen, wie z.B. Li, Na, K, Rb oder auch Erdalkalikationen, wie z.B. Mg, Ca, Sr oder auch andere Kationen wie z.B. H, NH₄, Zn, Cu, Ni, Co, Mn, Seltenerdmetalle u.a. enthalten. Auch Mischformen können eingesetzt werden.The zeolites suitable for the process according to the invention can contain alkali cations such as Li, Na, K, Rb or alkaline earth cations such as Mg Ca, Sr or other cations such as H, NH₄, Zn, Cu, Ni, Co, Mn, rare earth metals, among others. Mixed forms can also be used.

In einer besonders bevorzugten Ausführungsform handelt es sich bei den erfindungsgemäß verwendeten Zeolithen um solche, bei denen mindestens ein Teil der Metallkationen gegen Wasserstoffionen ausgetauscht ist, bevorzugt 50 bis 100 %, besonders bevorzugt 80 bis 100 % aller ursprünglich vorhandenen austauschbaren Metallkationen.In a particularly preferred embodiment, the zeolites used according to the invention are those in which at least some of the metal cations have been replaced by hydrogen ions, preferably 50 to 100%, particularly preferably 80 to 100%, of all exchangeable metal cations originally present.

Besonders bevorzugt für das erfindungsgemäße Verfahren sind Zeolithe mit vielen sauren Zentren, wie sie beispielsweise durch die Behandlung von Zeolithen mit Faujasit-Struktur mit Ammoniumsalzlösungen oder Seltenerdsalzslösungen und anschließender thermischer Behandlung entstehen. Die Zusatzmenge der zuvor beschriebenen Zeolithe liegt bevorzugt bei einer Menge von 0,1 bis 10 Gew.-%. Die ausblühungsverhindernde Wirkung bei unterschiedlichen Zeolith-Typen ist unterschiedlich stark ausgeprägt. Einfache Versuche ermöglichen eine optimale Dosierung. Sehr wirksam sind die Alkali-, Erdalkali- oder Seltenerdmetall-haltigen Zeolithe. Die wirksamsten Zeolithe sind solche des H-Zeolith Y-Typs.Zeolites with many acidic centers are particularly preferred for the process according to the invention, as arise, for example, from the treatment of zeolites with a faujasite structure with ammonium salt solutions or rare earth salt solutions and subsequent thermal treatment. The amount of the zeolites described above is preferably from 0.1 to 10% by weight. The efflorescence-preventing effect of different types of zeolite is different. Simple experiments enable optimal dosing. The alkali, alkaline earth or rare earth-containing zeolites are very effective. The most effective zeolites are those of the H type Y zeolite.

Für H-Zeolith Y wurden ca. 0,3 bis 1,5 Gew.-% als besonders bevorzugte Menge zur Erzielung der ausblühungsverhindernden Wirkung gefunden, bei den seltenerdmetallenthaltenden Zeolithen liegt die besonders bevorzugte Zugabemenge bei 0,7 bis 2,0 Gew.-%.For H-zeolite Y, about 0.3 to 1.5% by weight was found as a particularly preferred amount for achieving the efflorescence-preventing effect; for the zeolites containing rare earths, the particularly preferred addition amount is 0.7 to 2.0% by weight. %.

Die Grundrezepturen der erfindungsgemäßen Einbettmassepulver sind in an sich bekannter, konventioneller Art und Weise in einem geeigneten Mischaggregat, z.B in einem Nauta-Mischer, Lödige-Mischer o.ä. herstellbar, in dem man die pulverförmigen Additive inclusive der Zeolithe nacheinander zusammenmischt. Es ist jedoch auch möglich, Vormischungen, die den Zeolith enthalten, herzustellen, und diese Vormischungen einzumischen. Darüberhinaus ist es bei den beschriebenen Zeolith-enthaltenden erfindungsgemäßen Einbettmasseformulierungen auch möglich, diese ohne Verlust der oben beschriebenen gewünschten Eigenschaften in an sich bekannter Weise mit Isoparaffinen zu besprühen um z.B. deren Fließverhalten nochmals zu verbessern.The basic formulations of the investment powders according to the invention are in a conventional manner known per se in a suitable mixing unit, for example in a Nauta mixer, Lödige mixer or the like. can be produced by mixing the powdered additives including the zeolites together. However, it is also possible to prepare premixes containing the zeolite and to mix these premixes. In addition, it is also possible with the described zeolite-containing investment formulations according to the invention to spray them with isoparaffins in a manner known per se without loss of the desired properties described above, for example to improve their flow behavior again.

Anwendungstechnisch zeigen die Zeolith-enthaltenden erfindungsgemäßen Einbettmassepulvermischungen keine Nachteile gegenüber nicht zeolithenthaltenden Einbettmassemischungen. Es treten keine verarbeitungswesentlichen Veränderungen der Abbindezeit und Abbindetemperatur ein. Die Gelverträglichkeit ist unverändert gut. Die mechanische Festigkeit der Gußmuffel bzw. des aus der Einbettmasse gefertigten Modells ist unverändert gut, gleiches gilt für die Abbindeexpansion, einem bedeutenden Parameter für den Grad der Maßtreue des später erhaltenen Gußteils.In terms of application technology, the investment powder mixtures according to the invention containing zeolite show no disadvantages compared to investment mixtures which do not contain zeolite. There are no processing-related changes in the setting time and setting temperature. The gel tolerance is still good. The mechanical strength of the casting muffle or of the model made from the investment material remains good, the same applies to the setting expansion, an important parameter for the degree of dimensional accuracy of the casting subsequently obtained.

Die erfindungsgemäßen Einbettmasseformulierungen sind insbesondere sowohl gegenüber Dubliersilicon als auch gegenüber Agar-Agar-Dubliermasse verwendbar.The investment formulations according to the invention can be used in particular both with respect to duplicating silicone and with respect to agar-agar duplicating material.

Die vorstehend beschriebenen Ausblühungen treten beim Einsatz der erfindungsgemäßen Einbettmassen jedoch nicht auf; so daß mit deren Hilfe erheblich präzisere Gußteile erhalten werden.The efflorescence described above does not occur when using the investment materials according to the invention; so that considerably more precise castings can be obtained with their help.

Die folgenden Beispiele erläutern die Erfindung.The following examples illustrate the invention.

Es werden Abbindeexpansion, Verarbeitungszeit und Druckfestigkeit in Anlehnung an DIN 13919, Teil 2, Juni 1984, bestimmt. Die Abbindezeit ist der Zeitpunkt, bei dem die Abbindetemperatur das Temperatur-maximum erreicht. Die Ausblühungsneigung wurde durch ein Anmischen der beschriebenen Einbettmassepulver mit einer handelsüblichen Kieselsolanmischflüssigkeit (Levotherm-Anmischflüssigkeit) und Ausgießen des angemischten Gußeinbettmassebreies in eine additionsvernetzte Silicondublierformmasse (z.B. aus Tecnovil-Handelsware) getestet, indem das erstarrte Einbettmassemodell entformt und die Einbettmasseoberfläche nach 24 h nach dem Entformen und Stehen an der Raumluft begutachtet wird. Die Herstellung der Einbettmassepulverzusammensetzung erfolgt durch das homogene Mischen der Einzelkomponenten in einem Wurfschaufel-mischer (Lödige-Mischer), konischen Kegelstumpfmischer mit umlaufender Schnecke (Nauta-Mischer) oder in Taumelmischern, jedoch sind prinzipiell auch andere geeig-nete Mischaggregate verwendbar. Die nachfolgend aufgeführten Beispiele sollen die Erfindung beschreiben, ohne sie durch die Darstellung dieser Beispiele einzuengen.The setting expansion, processing time and compressive strength are determined in accordance with DIN 13919, Part 2, June 1984. The setting time is the point in time at which the setting temperature reaches the maximum temperature. The tendency to efflorescence was tested by mixing the investment powder described with a commercially available silica sol mixing liquid (Levotherm mixing liquid) and pouring the mixed casting investment paste into an addition-crosslinked silicone duplicating molding compound (for example from Tecnovil commercial goods), by means of the solidified investment mold and the demoulding mold after removal from the mold and standing in the air is examined. The investment powder composition is produced by homogeneously mixing the individual components in a throwing vane mixer (Lödige mixer), conical truncated cone mixer with rotating screw (Nauta mixer) or in tumble mixers, but in principle other suitable mixing units can also be used. The examples listed below are intended to describe the invention without restricting it by the illustration of these examples.

Die Bestandteile phosphatgebundener Gußeinbettmassen werden z. B. in K. Eichner, Zahnärztliche Werkstoffe und ihre Verarbeitung, Bd. 1, Hüthig Verlag, Heidelberg, 1981, S. 42; oder z. B. in: Quintessenz Zahntechnik 17, 73-86 (1991) beschrieben.The components of phosphate-bound casting investment materials are e.g. B. in K. Eichner, Dental materials and their processing, Vol. 1, Hüthig Verlag, Heidelberg, 1981, p. 42; or z. B. in: Quintessenz Zahntechnik 17, 73-86 (1991).

Das in den Beispielen verwendete Quarzmehl hat einen SiO₂-Gehalt > 99 % mit einem Gesamtrückstand von ca. 90 Vol.-% bei einem mittels eines Cilas-Granulometers gemessenen Korndurchmessers von 2 µm und einem Gesamtrückstand von ca. 89 Gew.-% bei einem Sinkgeschwindigkeitsäquivalentdurchmesser von 2,5 µm, gemessen nach Sedimentationsanalyse mittels Sedi Graph 5100. Eine verwendbare Quarzsandtype hat einen SiO₂-Gehalt von >99 % bei einer mittleren Korngröße von 0,28 mm. Eine einsetzbare Cristobalitmehltype zeigt bei einem SiO₂-Gehalt von >99 % eine Korngrößenverteilung nach Siebanalyse von (Durchmesser/Gew.-% Anteil) >200 µm/0,5, >100/5, >63/20, >40/44, <40/30,5 bei einer BET-Oberfläche von 0,9 m²/g. Als Phosphate werden Fabutit 746 (Fa. Budenheim) neben wenig Fabutit GI/66A (Fa. Budenheim) eingesetzt, als Magnesiumoxid Dynamag K (Fa. Hüls) neben wenig Mag Chem 40 (Göbel & Pfrengle). Es wurde zur Einfärbung der Masse ein roter Farbstoff (Fa. Conrads) verwendet, der i.M. die folgende Zusammensetzung aufweist: 53,9-51,6 % SiO₂; 24,0-27,4 % Al₂O₃; 6,3-11,6 % Fe₂O₃; 0,8-0,21 % MgO, Glühverlust 12,5-8,5 %.The quartz powder used in the examples has an SiO₂ content> 99% with a total residue of approx. 90 vol.% With a grain diameter of 2 μm measured using a Cilas granulometer and a total residue of approx. 89 wt Sink velocity equivalent diameter of 2.5 µm, measured according to sedimentation analysis using Sedi Graph 5100. A type of quartz sand that can be used has an SiO₂ content of> 99% with an average grain size of 0.28 mm. A usable cristobalite flour type with a SiO₂ content of> 99% shows a grain size distribution according to sieve analysis of (diameter / weight% fraction)> 200 µm / 0.5,>100/5,>63/20,> 40/44, <40 / 30.5 with a BET surface area of 0.9 m² / g. Fabutit 746 (from Budenheim) are used as phosphates in addition to a little Fabutit GI / 66A (from Budenheim), and magnesium oxide Dynamag K (from Hüls) in addition to a little Mag Chem 40 (Göbel & Pfrengle). A red dye (Conrads) was used to color the mass, which generally has the following composition: 53.9-51.6% SiO₂; 24.0-27.4% Al₂O₃; 6.3-11.6% Fe₂O₃; 0.8-0.21% MgO, loss on ignition 12.5-8.5%.

Beispiel 1example 1

Verschiedene mit Kieselsollösung angemischte Einbettmassen werden hinsichtlich ihres Ausblühungsverhaltens gegenüber Doubliersilicon nach dem Erstarren in der Siliconform beurteilt (SE = Seltenerdmetall):

Figure imgb0001
Different investment materials mixed with silica sol solution are evaluated with regard to their efflorescence towards doubling silicone after solidification in the silicone form (SE = rare earth metal):
Figure imgb0001

Aus den Versuchen zeigt sich auch, daß ein Isoparaffinzusatz die ausblühungsverhindernden Eigenschaften des Zusatzes von Zeolithen nicht behindert.The experiments also show that the addition of isoparaffin does not hinder the anti-efflorescence properties of the addition of zeolites.

Beispiel 2Example 2

Bei den Versuchen dieses Beispiels wird eine Standardeinbettmassemischung (= S) mit der folgenden Zusammensetzung verwendet.

S:
42,0 Gew.-Teile Quarzsand
25,0 Gew.-Teile Cristobalitmehl
9,1 Gew.-Teile Magnesiumoxid
8,0 Gew.-Teile Phosphate
15,9 Gew.-Teile Quarzmehl
Zusammensetzung der Einbettmasse S S + 1,5 Gew. Teile H-Zeolith Y S + 1,5 Gew. Teile K/Na-Zeolith A S + 1,5 Gew. Teile K-Zeolith L S + 2 Gew. Teile Ca-Zeolith Y S + 3 Gew Teile K-Zeolith Y Grad der Ausblühungen*) 5 1 1-2 2-3 1 2 *) 5 = starke Ausblühungen
4 = mittlere Ausblühungen auf der Modellvorder- und/oder rückseite
3 = geringe Ausblühungen auf der Modellvorder- und/oder rückseite
2 = sehr geringe Ausblühungen; hauptsächlich auf der Modellrückseite
1 = keine Ausblühungen A standard investment mixture (= S) with the following composition is used in the experiments of this example.
S:
42.0 parts by weight of quartz sand
25.0 parts by weight of cristobalite flour
9.1 parts by weight of magnesium oxide
8.0 parts by weight of phosphates
15.9 parts by weight of quartz flour
Composition of the investment S S + 1.5 parts by weight of H zeolite Y S + 1.5 parts by weight of K / Na zeolite A S + 1.5 parts by weight of K zeolite L S + 2 parts by weight of Ca zeolite Y S + 3 parts by weight of K zeolite Y Degree of efflorescence *) 5 1 1-2 2-3 1 2nd *) 5 = profuse efflorescence
4 = medium efflorescence on the front and / or back of the model
3 = slight efflorescence on the front and / or back of the model
2 = very little efflorescence; mainly on the back of the model
1 = no efflorescence

Die erfindungsgemäße Zugabe von Zeolithen zu dem Einbettmassepulver zeigt gravierende Verbesserungen der Ausblühneigung in allen Fällen gegenüber der Mischung S.The addition of zeolites according to the invention to the investment powder shows serious improvements in the tendency to bloom in all cases compared to the mixture S.

Beispiel 3Example 3 Physikalische Daten von EinbettmasseprobenPhysical data of investment samples

Figure imgb0002
Figure imgb0002

Durch den erfindungsgemäßen Zeolith-Zusatz wird keine negative Beeinflussung der Dubliergelverträglichkeit und der Abbindeexpansion hervorgerufen. Die Entwicklung der mechanischen Festigkeit durch den Zeolith-Zusatz ist positiv.The addition of zeolite according to the invention has no negative influence on the compatibility with duplicating gel and the expansion of the setting. The development of mechanical strength through the addition of zeolite is positive.

Claims (12)

Zeolithe enthaltende Gußeinbettmassen.Casting investment materials containing zeolites. Gußeinbettmassen gemäß Anspruch 1, dadurch gekennzeichnet, daß sie 0,1 bis 10 Gew.-% bezogen auf die pulverförmige Masse an Zeolithen enthalten.Cast investment materials according to Claim 1, characterized in that they contain 0.1 to 10% by weight, based on the pulverulent mass of zeolites. Gußeinbettmassen nach Anspruch 1, dadurch gekennzeichnet, daß sie 0,3 bis 2,0 Gew.-% bezogen auf die pulverförmige Masse an Zeolithen enthalten.Cast investment materials according to Claim 1, characterized in that they contain 0.3 to 2.0% by weight, based on the pulverulent mass of zeolites. Gußeinbettmassen gemäß Anspruch 1, dadurch gekennzeichnet, daß sie 0,7 bis 1,5 Gew.-% bezogen auf die pulverförmige Masse an Zeolithen enthalten.Cast investment materials according to Claim 1, characterized in that they contain 0.7 to 1.5% by weight, based on the pulverulent mass of zeolites. Gußeinbettmassen nach Ansprüchen 1 bis 4, dadurch gekennzeichnet, daß es sich bei den Zeolithen um einen oder mehrere Zeolithen aus der Gruppe bestehend aus Faujasite, Mordenite, Zeolith β, Zeolith Ω, Zeolith L, Zeolith A, Offretit, ZSM 12, Pentasile, PSH-3, ZSM 22, ZSM 23, ZSM 48, EU-1, Zeolith T, Chabasite, Gmelinite, Ferrierite, Zeolith Rho, ZK-5 handelt.Cast investment materials according to Claims 1 to 4, characterized in that the zeolites are one or more zeolites from the group consisting of faujasite, mordenite, zeolite β, zeolite Ω, zeolite L, zeolite A, offretite, ZSM 12, pentasile, PSH -3, ZSM 22, ZSM 23, ZSM 48, EU-1, Zeolite T, Chabasite, Gmelinite, Ferrierite, Zeolite Rho, ZK-5. Gußeinbettmassen nach Ansprüchen 1 bis 4, dadurch gekennzeichnet, daß es sich bei dem Zeolith um einen oder mehrere saure Typen mit Faujasit-Struktur handelt.Cast investment materials according to Claims 1 to 4, characterized in that the zeolite is one or more acidic types with a faujasite structure. Gußeinbettmassen nach Ansprüchen 1 bis 6, dadurch gekennzeichnet, daß sie in Form einer Pulvermischung vorliegen.Cast investment materials according to Claims 1 to 6, characterized in that they are in the form of a powder mixture. Gußeinbettmassen nach Ansprüchen 1 bis 6, dadurch gekennzeichnet, daß die Massen in Form einer Anmischung durch Anteigen mit einer geeigneten wässrigen oder alkoholischen Anmischflüssigkeit vorliegen.Cast investment materials according to Claims 1 to 6, characterized in that the materials are in the form of a mixture by pasting with a suitable aqueous or alcoholic mixing liquid. Einbettmassemodelle, hergestellt aus Gußeinbettmassen nach Ansprüchen 1 bis 8.Investment models produced from cast investment materials according to Claims 1 to 8. Verwendung der Einbettmassen gemäß Ansprüchen 1 bis 8 beim Metallguß.Use of the investment materials according to claims 1 to 8 in metal casting. Verwendung der Einbettmassemodelle bzw. der Einbettmasseanmischungen nach Ansprüchen 1 bis 9 in der Dentaltechnik.Use of the investment material models or the investment material mixtures according to claims 1 to 9 in dental technology. Verwendung der Einbettmassemodelle bzw. der Einbettmasseanmischungen nach Ansprüchen 1 bis 9 in der Restaurationstechnik.Use of the investment material models or the investment material mixtures according to claims 1 to 9 in restoration technology.
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