Process For Producing A Glazed Ceramic Body

Abstract

The invention relates to a process for producing a glazed ceramic body, in which (a) a glazing material is applied to a non-densely sintered substrate material and (b) the substrate material and the glazing material are subjected to a heat treatment in a temperature range which extends from a first temperature T.sub.1 to a second temperature T.sub.2, which is higher than the first temperature, in order to obtain the glazed body.

The invention also relates to the use of a glazing material for glazing a non-densely sintered substrate material.

Claims

1. Process for producing a glazed ceramic body, comprising (a) a glazing material is applied to a non-densely sintered substrate material and (b) the substrate material and the glazing material are subjected to a heat treatment in a temperature range which extends from a first temperature T.sub.I to a second temperature T.sub.2, which is higher than the first temperature, in order to obtain the glazed body, wherein, at the temperature T.sub.1, the glazing material has a viscosity of more than 10.sup.2.5 Pa.Math.s, and, at the temperature T.sub.2, a viscosity of less than 10.sup.9 Pa.Math.s.

2. Process according to claim 1, in which, at the temperature T.sub.1, the glazing material has a viscosity of more than 10.sup.5.6 Pa.Math.s, and, at the temperature T.sub.2, a viscosity of less than 10.sup.5.6 Pa.Math.s.

3. Process according to claim 1, in which the non-densely sintered substrate material is a presintered substrate material.

4. Process according to claim 1, in which the non-densely sintered substrate material has a relative density in the range of from 30 to 90%, based on the true density of the substrate material.

5. Process according to claim 1, in which the substrate material begins to sinter at the temperature T.sub.1.

6. Process according to claim 1, in which the substrate material is kept at the temperature T.sub.2 for a period of 5 to 120 minutes.

7. Process according to claim 1, in which, at the temperature T.sub.2, the substrate material has a relative density of at least 97%, based on the true density of the substrate material.

8. Process according to claim 1, in which, at a temperature T.sub.x, at which the substrate material has a relative density of 95%, based on the true density of the substrate material, the glazing material has a viscosity of more than 10.sup.2.5 Pa.Math.s.

9. Process according to claim 1, in which the glazing material has, at the temperature T.sub.1, a viscosity of more than 10.sup.5.6 Pa.Math.s, at the temperature T.sub.x, at which the substrate material has a relative density of 95%, based on the true density of the substrate material, a viscosity of more than 10.sup.2.5 Pa.Math.s, and, at the temperature T.sub.2, a viscosity of less than 10.sup.9 Pa.Math.s.

10. Process according to claim 1, in which the substrate material is an oxide ceramic or an inorganic-inorganic composite material.

11. Process according to claim 1, in which the substrate material comprises at least two layers, which differ in their colour.

12. Process according to claim 1, in which, at a temperature of 950 C., the glazing material has a viscosity of more than 10.sup.2.5 Pa.Math.s, at a temperature of 1300 C., a viscosity of more than 10.sup.2.5 Pa.Math.s and, at a temperature of 1450 C., a viscosity of less than 10.sup.9 Pa.Math.s.

13. Process according to claim 1, in which, at a temperature of 700 C., the glazing material has a viscosity of more than 10.sup.2.5 Pa.Math.s, at a temperature of 900 C., a viscosity of more than 10.sup.2.5 Pa.Math.s and, at a temperature of 1100 C., a viscosity of less than 10.sup.9 Pa.Math.s.

14. Process according to claim 1, in which the glazing material comprises a frit, which comprises SiO.sub.2, Al.sub.2O.sub.3 and K.sub.2O and/or Na.sub.2O, and contains at least one or all of the following components in the given amounts: TABLE-US-00005 Component wt.-% SiO.sub.2 50.0 to 80.0 Al.sub.2O.sub.3 10.0 to 30.0 K.sub.2O 0 to 20.0 Na.sub.2O 0 to 10.0 CaO 0 to 10.0 BaO 0 to 10.0

15. Process according to claim 1, in which the glazing material is applied to the substrate material in the form of a powder, a slip, a spray or a lacquer, by an airbrushing method or incorporated into a film or an adhesive strip.

16. Process according to claim 1, in which the glazing material is used in the form of a composition which further comprises at least one carrier and/or solvent and/or at least one inorganic and/or organic filler.

17. Process according to claim 1, in which the glazing material does not substantially penetrate into the substrate material.

18. Process according to claim 1, in which the glazed ceramic body is a glazed dental body or a glazed dental restoration or a bridge, an inlay, an onlay, a crown, a veneer, a facet or an abutment.

19. Process of using a glazing material for glazing a non-densely sintered substrate material, wherein the glazing material is applied to the non-densely sintered substrate material and the substrate material and the glazing material are subjected to a heat treatment in a temperature range which extends from a first temperature T.sub.1 to a second temperature T.sub.2, which is higher than the first temperature, wherein, at the temperature T.sub.1, the glazing material has a viscosity of more than 10.sup.2.5 Pa.Math.s and, at the temperature T.sub.2, a viscosity of less than 10.sup.9 Pa.Math.s.

Description

EXAMPLES

Examples 1A-B

[0037] Preparation of the Glazing Materials

[0038] Two different glasses with the compositions given in Table I were prepared as glazing materials according to the invention.

TABLE-US-00003 TABLE I Example 1A 1B Component wt.-% wt.-% SiO.sub.2 65.41 73.39 K.sub.2O 11.62 10.25 Na.sub.2O 2.25 1.98 Al.sub.2O.sub.3 20.72 14.38 Total 100.00 100.00

[0039] For this purpose, first of all 200 g of the raw materials quartz powder (SiO.sub.2), potassium carbonate (K.sub.2CO.sub.3), sodium carbonate (Na.sub.2CO.sub.3) and aluminium oxyhydroxyhydrate (AlO (OH)H.sub.2O) were thoroughly mixed for 30 min by means of a Turbula mixer.

[0040] From the homogeneous mixtures, cylindrical compacts with a diameter of about 40 mm and weighing about 25 g were produced uniaxially by means of a hydraulic press at a pressure of 3 MPa. These compacts were heated up to 1000 C. in a furnace on a quartz dish over 6 h and held at this temperature for a further 6 h. After cooling in the furnace, the compacts were comminuted by means of a jaw crusher to a size of about 1.5 mm and subsequently ground in a mortar grinder (Retsch R200) for 15 min.

[0041] The calcined mixture was pressed by means of a hydraulic press at a pressure of 3 MPa to form compacts with a diameter of about 40 mm. These compacts were heated up to 1150 C. in a furnace on a quartz dish over 6 h and held at this temperature for a further 6 h. After cooling in the furnace, the compacts were comminuted by means of a jaw crusher to a size of about 1.5 mm and subsequently ground in a mortar grinder (Retsch R200) for 15 min.

[0042] From the calcined mixture, tempered cakes weighing about 40 g were produced by means of a hand press and placed in the hot furnace (Nabertherm HT16/17) on quartz dishes with a little quartz powder as separating agent at about 1000 C. The tempered cakes were then heated at 10 K/min to 1450 C. (Example LA) and 1400 C. (Example 1B), respectively and held at this temperature for 1.5 h. After the holding time had finished, the tempered cakes were cooled for about 2 min in air and then quenched in a water bath. The blanks obtained in this way were comminuted by means of a jaw crusher to a size of about 1.5 mm and subsequently ground in a mortar grinder (Retsch R200) for 15 min.

Examples 2A-B

[0043] Determination of the Viscosity Properties of the Glazing Materials

[0044] For the determination of the viscosity properties of the glazing materials obtained in Examples 1A-B as a function of the temperature, a viscosity-temperature curve was calculated on the basis of the Vogel-Furcher-Tammann equation (VFT equation):

[00002]${\log }_{1.Math.0}\left(\right)=A+\frac{B}{T-T_0}$ [0045] : dynamic viscosity at the temperature T [0046] A, B, T.sub.0: substance-specific constants

[0047] For this purpose, at least three of the following characteristic temperatures were determined experimentally by means of a dilatometer or a heating microscope, respectively:

TABLE-US-00004 Designation and measurement method (Pa .Math. s) T.sub.g (glass transition point from dilatometer) 12 T.sub.d (softening temperature from dilatometer) 10 T.sub.S (softening point from heating microscope) 5.6 T.sub.HB (hemisphere point from heating microscope) 3.5 T.sub.F (flow point from heating microscope) 2.1

[0048] The temperatures T.sub.g and T.sub.d were determined by means of a dilatometer (Bahr-Thermoanalyse GmbH) with a quartz glass push-rod and holder. The material to be examined was heated at a heating rate of 5 K/min to the softening point (maximum 1000 C.). During the measurement, the set-up was flushed with nitrogen.

[0049] The temperatures T.sub.S, T.sub.HB and T.sub.F were determined by means of a heating microscope (Hesse Instruments with EMA I software). The material to be examined was heated in a tube furnace at a heating rate of 10 K/min. The software automatically determines the characteristic changes in shape of the sample and assigns the corresponding temperature to them.

[0050] Starting from the pairs of values of the experimentally determined characteristic temperatures and the associated viscosity values stated above, the VFT equation was solved by an approximation method according to the least-squares method with the aid of the solver function of the Microsoft Excel 2016 MSO (16.0.4456.1003) 32-bit software.

[0051] The viscosity-temperature curves determined in this way for the glazing materials obtained in Examples 1A-B are shown in FIG. 1. For comparison, this also shows a viscosity-temperature curve determined analogously for a commercially available glazing material (IPS e.max CAD Crystall./Glaze Spray, Ivoclar Vivadent AG).

Examples 3A-B

[0052] Use of the glazing materials for glazing

[0053] Small plates (19 mm15.4 mm1.5 mm) were cut from commercially available blanks made of presintered ZrO.sub.2 (IPS e.max ZirCAD MO 0, Ivoclar Vivadent AG) and these were used without further thermal pretreatment as substrate material. By means of an airbrushing method using a spray gun (VITA SPRAY-ON, Vita Zahnfabrik) at a working pressure of about 1 bar and from a distance of about 10 cm, aqueous suspensions of the glazing materials A and B prepared in Examples 1A-B were sprayed onto these small plates and, after drying in air for 30 min in a furnace (Sintramat S1 1600, Ivoclar Vivadent AG, program P1), densely sintered within 70 min and simultaneously glazed.

[0054] After the sintering, the glazed small ZrO.sub.2 plates were embedded in a two-component resin (EpoKwick Epoxy Resin/EpoKwick Epoxy Hardener 10:2, Buehler), polished at the boundary surface to optical quality (Apex Diamond Grinding Discs, Buehler, grain size to 0.5 m) and subsequently examined by means of scanning electron microscopy (SEM, backscattered electrons). The results are shown in FIG. 2A (Example 3A) and FIG. 2B (Example 3B). The results show that the glazing materials according to the invention have not infiltrated into the substrate material in appreciable amounts.

Example 3C (Comparison)

[0055] Use of a Commercial Glazing Material for Glazing

[0056] Analogously to Examples 3A-B, small plates were cut from commercially available blanks made of presintered ZrO.sub.2 (IPS e.max ZirCAD MO 0, Ivoclar Vivadent AG). By means of an airbrushing method using a spray gun (VITA SPRAY-ON, Vita Zahnfabrik) at a working pressure of about 1 bar and from a distance of about 10 cm, an aqueous suspension of a commercially available glazing material (IPS e.max CAD Crystall./Glaze Spray, Ivoclar Vivadent AG) was sprayed onto these small plates and, after drying in air for 30 min in a furnace (Sintramat S1 1600, Ivoclar Vivadent AG, program P1), densely sintered within 70 min and simultaneously glazed.

[0057] After the sintering, the glazed small ZrO.sub.2 plates were embedded in a two-component resin (EpoKwick Epoxy Resin/EpoKwick Epoxy Hardener 10:2, Buehler), polished at the boundary surface to optical quality (Apex Diamond Grinding Discs, Buehler, grain size to 0.5 m) and subsequently examined by means of scanning electron microscopy (SEM, backscattered electrons). The results are shown in FIG. 2C. These results show that the commercial glazing material has infiltrated into the substrate material to a considerable extent.

Example 4

[0058] Influence of the Relative Density on the Infiltration Depth

[0059] Small plates (19 mm15.4 mm1.5 mm) were cut from commercially available blanks made of presintered Zr0.sub.2 (IPS e.max ZirCAD MO 0, Ivoclar Vivadent AG) and these were presintered by thermal treatment to a relative density of 50%, 85%, 90% and 99.7%, respectively, in each case based on the true density of the substrate material. By means of an airbrushing method using a spray gun (VITA SPRAY-ON, Vita Zahnfabrik) at a working pressure of about 1 bar and from a distance of about 10 cm, an aqueous suspension of the glazing material A prepared in Example LA was sprayed onto these small plates and, after drying in air for 30 min in a furnace (Sintramat S1 1600, Ivoclar Vivadent AG, program P7), densely sintered within 70 min and simultaneously glazed.

[0060] After the sintering, the glazed small ZrO.sub.2 plates were embedded in a two-component resin (EpoKwick Epoxy Resin/EpoKwick Epoxy Hardener 10:2, Buehler), polished at the boundary surface to optical quality (Apex Diamond Grinding Discs, Buehler, grain size to 0.5 m) and subsequently examined by means of scanning electron microscopy (SEM, backscattered electrons) and energy dispersive x-ray spectroscopy (EDX). The results are shown in FIGS. 3A-D. From these it can be seen that the infiltration depth of the glazing material according to the invention is largely independent of the relative density and thus of the residual porosity of the substrate material.