DE102006052030A1 - Process for producing colored ceramics - Google Patents

Abstract

A process for producing colored ceramics, wherein metal salt or its solution is added to slip containing ceramic powder.

Description

The The invention relates to a process for producing colored ceramics. In particular, the invention relates to a method for manufacturing of colored Dental ceramics. Dental ceramics are used as dentures.

In the DE 19904522 A1 For example, a process for coloring ceramics using ionic or complex-containing solutions is described.

This However, it is very time consuming because the ceramics in a separate Production step with the solutions need to be contacted. Besides that is the control of the degree of dyeing very expensive. For every degree of color becomes a special solution produced.

from that results in the task of a method for producing colored ceramics to provide that is fast feasible. Another task It is a process for producing colored ceramics to provide, in which the Dye degree can be easily controlled.

These Task, a method with the features of claim 1 is achieved. Advantageous types of implementation of the method emerge from the dependent claims.

These Task is solved by in that prior to the molding of the ceramics a colorant to the ceramic mass is given.

Especially the object is achieved by a method for producing colored ceramics, wherein Metal salts or their solutions is added to ceramic powder containing slip. The coloring of Ceramics are thus made possible with little expenditure of time. The control of the degree of coloring can be easily controlled by the added amount.

It There are a variety of ceramics that can be colored. To counting preferably dental ceramics and generally oxide ceramics, in particular Ceramics of alumina, zirconia and mixtures of alumina and zirconia. Preferably, silicate ceramics are dyed. Especially are also bricks, sewage pipes, tableware, tiles and sanitary Ware inked. Even technical ceramics can be dyed. Oxide ceramics like ZrO2 and Al2O3 are chosen for their good biocompatibility and their high biocompatibility Strength preferably used in medical applications.

metal salts are colored and get their color especially from a colored Metal ion or a colored acid residue. The color of the metal salts is determined by the chemical composition certainly. For example, the use of copper can turn green and blue can be generated by the use of chrome can produce green become.

Preferably iron nitrate or complexes such as iron thiocyanate are used, nitrates are usually very soluble are and the acid residue with oxygen to a volatile Product reacts. This will avoid the acid residue may negatively affect the properties of the product.

Metal salt solutions are in a suitable solvent in solution brought metal salts. Preferably, readily soluble salts of transition metals used.

One preferred solvent for the preparation of metal salt solutions is water. Water is readily available and does not cause any environmental damage.

ceramic powder can be used as a raw material for the production of ceramics in powder compaction processes become. examples for Ceramic powders are alumina powder, zirconia powder, silicon carbide powder and silicon nitrite powder.

Schlicker consists of ceramic powder that mixes with other substances so has been that a flowable mass arises. For this purpose, the ceramic powder is preferably mixed with water. Preferably, the ceramic powder with alcohols, organic solvents or polymer melts applied. The slip becomes particular with additives such as binders and dispersants. This happens for example by wet grinding in drum mills or by stirring in mixing whiskers. This creates flowable slip. This slip can by pouring be further processed for example in a chamber filter press be dehydrated to the plastically deformable state, by spray drying to a free-flowing Granules are dried, for the production of feedstocks for injection molding or Extruding be used.

It is appropriate, the Metal salts or their solutions to mix with the slip to a mixture. This will ensure that the metal salt or its solution in the slurry homogeneous is distributed.

In the mixture, the metal salt or its solution is mixed with the slurry. The mixing of the metal salt / the metal salt solution with the slurry can be coarse. Preferably, the metal salt or its solution with the slurry is so finely mixed that no metal salt or Metal salt solution accumulations are present in the slurry and the mixture has everywhere the same proportion of metal salt / metal salt solution.

The For example, mixing can be done in a drum mixer, a plate mixer or a pipe mixer become. In a drum mixer, the substances to be mixed become mixed in a rotating drum. At a plate mixer are in a circular Mixing plate mixing blades arranged. The substances to be mixed are placed in the mixing plate. The mixing is done by rotation either the mixing plate or the mixing blades causes. In a pipe mixer The substances to be mixed are placed in a mixing tube. In this Mixing tube is a mixing shaft for circulating the substances to be mixed.

The Mixing of the metal salt or its solution with the slip can lead to different degrees of mixing. At a coarse degree of mixing are present in the mixture agglomerates. The metal salt or its Solution can but also so intensely mixed with the slip that the Metal salt or its solution is finely dispersed in the slurry after mixing.

Preferably if the mixture is exposed to heat, especially at 90 ° C to 120 ° C, preferably at 95 ° C up to 115 ° C, especially preferred at 100 ° C up to 110 ° C, sprayed to dry. In this way, the mixture can be dried quickly.

The Temperature at which the mixture is acted upon is preferably chosen so that the desired Drying degree is achieved and undesirable effects, such as Dust explosions are prevented. For mixtures used for manufacturing are used by dental ceramics, temperatures are between 90 ° C and 120 ° C especially suitable.

When drying different degrees of drying can be achieved. If the mixture is to be pressed, the moisture content should only be up to 15%. For plastic molding processes, the moisture content should be 15 up to 25% and for casting more than 25%.

To the spray the mixture is preferably moved with compressed air. Another Possibility that Mixture is moving with a piston against one in one Press the mixture located in the piston chamber. The mixture can by a nozzle, over one Edge or be sprayed through a sieve. By moving the mixture by means of compressed air, the mixture interspersed with air. This loosens up the mixture. at moving the mixture through a piston, little air permeates into the mixture, so that the mixture in a subsequent Falling through a heated gas is directly exposed to the gas. at Spraying through a nozzle can by selecting the nozzle cross-section purposefully influenced the degree of atomization of the mixture become. When spraying over a Edge is comparatively little energy required for spraying. When spraying through a sieve, a comparatively large amount of mixture can simultaneously atomized become.

The spray of the mixture preferably produces a granulate. This becomes a preferred starting material for the Dry pressing provided.

One Granules consist of an aggregate of granules. One Granule consists of powder particles and has a regular shape. Preferably, the granules have a mean size of 20 to 200 microns, more preferably from 50 to 100 microns on.

It is particularly appropriate, the To press granules. The pressing of granules is a very economical Process for the production of large quantities.

At the Pressing is applied to the granules pressure. This can be, for example done by the use of presses. It can be mechanical, hydraulic or pneumatic presses are used. As a mechanical press could For example, a screw press, wherein the pressing force over a Spindle is transferred to the granules, be used. An example of a hydraulic press is a press with hydraulically operated punch. As a pneumatic Press can be used a press with pneumatically actuated punch. The granules can with different pressing forces to different degrees of compaction be pressed.

there It is particularly useful when through pressing the granules a green compact is produced. By generating the green body, the granules in brought a shape that matches the shape of the desired ceramic product comes close. It is possible, a green plant to work mechanically.

A green body is a body which is solidified prior to its intended use by a thermal process. In the ceramic production, the green compact is preferably produced by casting, plastic molding or pressing. By casting, complex components can be made well by plastic molding, as in Extruding, for example, components can be produced inexpensively. By pressing, such as dry pressing, large quantities can be produced inexpensively.

It is particularly appropriate to the Green body mechanically to edit. The greenling can be inexpensive be mechanically processed.

mechanical Arrangements attached to the green carried out can be are for example turning, milling or drilling.

It is particularly convenient, by the mechanical processing of the green body has a near-net shape Greenfinch to create. By creating a near-net shape green body is reduced the required further processing.

One near-net shape green compact is a green, the under consideration possibly the following process steps have the smallest possible oversizes. at Ceramics production is typically a subsequent process step the burning. The fire allows sintering, i. the emergence of the ceramic bond. The green is compacted and solidified during sintering into a body hereinafter referred to as "sintered body". The volume decreases. In a preliminary stage to the sintered body can Greenfinch are also pre-sintered to a body hereinafter referred to as "white body" the burning shrinks the green stuff. A near-net shape green, which will be burned, therefore, is widely used depending on the expected shrinkage Oversize. Furthermore could a near-net shape green body in areas where high dimensional accuracy is required, have an additional allowance. At these points, the component is preferably after firing worked hard, resulting in higher dimensional accuracy can be achieved.

Preferably becomes the near net shape green burned. The burning compacts the near-net shape green compact and solidified.

The Burning temperature is dependent of the material used and the desired properties. she should there be sintering, i. allow the emergence of the ceramic bond. For components made of Y-TZP preferably temperatures between 1300 ° C and 1500 ° C applied. Particularly preferred are for powders having a larger specific surface lower temperatures used than for powders with a smaller one specific surface.

Conveniently, By burning the near-net shape green compact, a near-net shape sintered body is produced. So will the effort for the Post-processing of the sintered body reduced to a minimum.

One sintered body is a body which has been produced by sintering. This is preferably a Greenfinch made by a heat treatment or sintering to the sintered body compacted and cured becomes. A near-net shape sintered body is a sintered body, a small oversize too the desired one Component has. Preferably, a near-net shape sintered body only in the areas oversizes on where a higher dimensional stability is required, as achieved with a pre-sintering process can be.

Of the Near-net shape sintered body is preferably subjected to a hard machining. Through the hard machining can very high dimensional accuracy be achieved.

When Hard-working measures for example be used: turning, milling, drilling, Sanding, polishing and sandblasting.

components are usable Products. these can here for example: dentures, porcelain, bricks, High voltage insulators, roof tiles, stoneware, wall tiles or spark plugs.

preferred Way, the component is used for medical purposes, especially in the Dental area used. Due to the good biocompatibility, the component is for medical Purposes particularly suitable. The high strength allows one particularly good usability in the dental field.

in the Dental area, the component, for example, as a bridge or Crown can be used. In medical technology and in the dental field is ceramics especially due to biocompatible properties and the wear resistance used.

Preferably contains the slip ceramic powder of certain particle sizes. So can the properties of the finished component and the parameters of the following Production processes are specified.

By the grain size of the ceramic powder becomes the form resolution limited to the finished components.

It is appropriate, the Ceramic powder of a certain grain size by grinding ceramic powder, its grain size is not is defined to generate.

The ceramic powder can be ground, for example, in a ball mill. In a ball mill, the millbase is placed together with grinding media (balls) in a grinding container. By a rotor, the balls are moved and crush the material to be ground.

preferred Way the ceramic powder consists of Y-TZP. The high strength and the toughness of Y-TZP enable to produce high quality components.

Y-TZP is polycrystalline, tetragonal zirconia, with stabilization Yttriumoxidbasis took place. Yttrium oxide is the oxygen compound of yttrium. Yttrium is a metallic element of rare earth metals.

Preferably, the Y-TZP is produced by drying Zr _1-x Y _x (OH) _y .

By Thermal drying produces Y-TZP. This process becomes calcination and is preferably in a rotary kiln, particularly preferred carried out in a chamber furnace.

Rotary kilns are in process engineering for continuous processes used. In a rotary kiln is The substance to be treated is placed in a rotary tube, slightly inclined is and turns. The rotating pipe is either from the outside over the Rotary tube wall heated, or the heat is within the furnace, for example produced by burners. One of Outside heated rotary kiln allows a precisely specified product room atmosphere. In an internally heated Rotary kiln, the product is in direct contact with the flue gas.

Chamber furnaces are in process engineering for discontinuous processes used. When a chamber furnace is the substance to be treated is placed in trays and placed in the oven. The oven is heated according to a predetermined program. The Heat can For example, be generated electrically or by burners.

Conveniently, the Zr _1-x Y _x (OH) _y is generated by hydrolysis.

hydrolysis is the cleavage of a chemical compound under addition of a Water molecule.

It is convenient to generate the Zr _1-x Y _x (OH) _y by hydrolysis of Z _r OCL ₂ · 8H ₂ O + YCl. ₃

It is expedient to produce the Z _r OCL ₂ · 8H ₂ O + _YCl3 by chemical pulping of zircon sand.

zircon For example, in Australia. They are the most important Sources for the extraction of raw materials from zircon.

The Invention will now be illustrated with reference to figures, in the further advantages of the embodiment are shown. In the figures show:

1 the production of Y-TZP with defined grain size from zircon sand;

2 mixing iron nitrate with slip; and

3 the production of a component from the mixture.

In the 1 to 3 are shown related parts of a process for the production of dyed zirconia products. 1 shows as a first part of the manufacturing process the production of Y-TZP with defined grain size from zircon sand. 2 shows as a second part of the manufacturing process, the mixing of iron nitrate with slip. 3 shows as the last part of the manufacturing process, the production of a component from the mixture.

In the in 1 shown first part of the manufacturing process, in which Y-TZP with defined, in particular smaller than 500 nm, preferably smaller than 250 nm grain size is prepared from zirconium sand, the zirconium sand is digested and converted to ZrOCl ₂ · 8H ₂ O. In a next process step, the hydrate Zr _1-x Y _x (OH) _y is produced by the hydrolysis from ZrOCl ₂ 8H ₂ O and YCl. ₃ Thereafter, the Zr _1-x Y _x (OH) _{y is} thermally dried in a rotary kiln or chamber furnace. This creates Y-TZP with undefined grain sizes. The Y-TZP with undefined grain size is ground in a drum mill to produce Y-TZP of defined grain size.

So becomes a substance from the naturally occurring zirconsand defined properties, used for ceramic production can be used. Because of that as a raw material for ceramic production a substance with defined properties is used the possibility of components to produce with defined properties.

2 shows the mixing of iron nitrate 4 with a slip 2 , Schematically is a drum 1 a drum mixer shown with slip 2 is filled. The slip 2 consists of Y-TZP with defined grain size, water and polyacrylate polymers. The polyacrylate polymers are used here as binders. These substances are mixed well together. The slip 2 is flowable. Next to the drum mixer with the slip 2 there is a vessel 3 with iron nitrate 4 ,

For mixing, the iron nitrate 4 from the vessel 3 placed in the drum mixer. By the rotation of the drum 1 becomes the iron nitrate 4 with the slip 2 mixed.

Out this mixture can colored Ceramic components are produced.

3 shows the third part of the process, the production of a component from the mixture 2. The mixture 2 is first sprayed through nozzles. After passing through the nozzles, the sprayed mixture passes 2 110 ° C warm air. This creates Y-TZP granules. In a next process step, the Y-TZP granulate is placed in a mold and pressed by means of a hydraulic press to a green compact. Thereafter, the green compact is machined by milling. During milling, the shrinkage is taken into account in the subsequent process steps. In the areas of the green area, where particularly tight tolerances must be tolerated, an additional allowance is left for later processing steps. Thereafter, the near-net shape green compact is fired at 1400 ° C. The workpiece shrinks and is simultaneously compacted and solidified. In the areas of the workpiece in which it is particularly tight tolerated, and in which an additional allowance has been left on the green body, it is then ground. After grinding, the component is ready.

The Component is a crown or bridge for the dental treatment of a patient.

In This third part of the process is made from a flowable mixture 2 produced a finished, colored component.

1

drum

2

Schlicker

3

vessel

4

ferric nitrate

Claims (20)

Process for producing colored ceramics, characterized in that metal salts or their. Solution is added to ceramic powder containing slip. Method according to claim 1, characterized in that that the metal salts or their solution with the slip to a Mixture is mixed. Method according to claim 2, characterized in that that the mixture is exposed to heat, especially at 90 ° C up to 120 ° C, preferably at 95 ° C up to 115 ° C, especially preferred at 100 ° C up to 110 ° C, sprayed to dry becomes. Method according to claim 3, characterized that by spraying the mixture is produced granules. Method according to claim 4, characterized in that that the granules are pressed. Method according to claim 5, characterized in that in that a green compact is produced by the pressing of the granules. Method according to Claim 6, characterized that the greenling or machined from him white cast mechanically becomes. Method according to claim 7, characterized in that that the mechanical processing of the green body produces a near-net shape green body or white body becomes. Method according to claim 8, characterized in that that the near-net shape green or white is burned. Method according to claim 9, characterized in that that by burning the near-net shape green or white one Near-net shape sintered body will be produced. Method according to claim 10, characterized in that that the near-net shape sintered body of a Hard machining is subjected. Method according to claim 11, characterized in that that a component is produced by the hard machining. Method according to claim 12, characterized in that that the component for medical purposes, especially in the dental field is used. Method according to one of the preceding claims, characterized characterized in that the slip ceramic powder of certain Contains grain sizes. Method according to claim 14, characterized in that that the ceramic powder of a certain particle size is obtained by grinding ceramic powder, its grain size is not is defined is generated. Method according to one of claims 14 or 15, characterized that the ceramic powder consists of Y-TZP. A method according to claim 16, characterized in that the Y-TZP by drying Zr _1-x Y _x (OH) _{y is} generated. A method according to claim 17, characterized in that the Zr _1-x Y _x (OH) _y is generated by hydrolysis. A method according to claim 18, characterized in that the Zr _1-x Y _x (OH) _{y is} generated by hydrolysis of ZrOCL ₂ · 8H ₂ O and YCl ₃ . A method according to claim 19, characterized in that the ZrOCL ₂ · 8H ₂ O is produced by chemical pulping of zircon sand.