CA2037372A1 - Enamel compositions - Google Patents
Enamel compositionsInfo
- Publication number
- CA2037372A1 CA2037372A1 CA 2037372 CA2037372A CA2037372A1 CA 2037372 A1 CA2037372 A1 CA 2037372A1 CA 2037372 CA2037372 CA 2037372 CA 2037372 A CA2037372 A CA 2037372A CA 2037372 A1 CA2037372 A1 CA 2037372A1
- Authority
- CA
- Canada
- Prior art keywords
- frit
- weight
- percent
- composition
- positive amount
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Abstract
ENAMEL COMPOSITIONS
ABSTRACT OF THE DISCLOSURE
A fluorine-free frit composition containing a high content of boron oxide and a relatively low amount of titanium oxide is provided. In a preferred embodiment, the composition contains a small amount of cobalt oxide. The composition is suitable for the preparation of frits which may be applied by either the dry and wet methods of application to obtain enamel cover coats. In particular, the frit is suitable for use in the electrostatic method of frit application on steel substrates.
The composition of the invention is particularly suitable in "two coat-one fire" applications. The enamel produced from the frit of the invention is characterized by its virtual freedom from pitting, relatively high acid resistance and exceptional color stability.
ABSTRACT OF THE DISCLOSURE
A fluorine-free frit composition containing a high content of boron oxide and a relatively low amount of titanium oxide is provided. In a preferred embodiment, the composition contains a small amount of cobalt oxide. The composition is suitable for the preparation of frits which may be applied by either the dry and wet methods of application to obtain enamel cover coats. In particular, the frit is suitable for use in the electrostatic method of frit application on steel substrates.
The composition of the invention is particularly suitable in "two coat-one fire" applications. The enamel produced from the frit of the invention is characterized by its virtual freedom from pitting, relatively high acid resistance and exceptional color stability.
Description
-` 203~372 Mo 3400-CIP
ENAMEL COMPOSITIONS
CROSS-REFERENCE TO RELATED AppLIcA-rIoN
This application is a Continuation-in-Part of U.S.
Application Serial Number 07/490,215, filed March 8, 1990.
Field of the Invention The present invention relates to enamel compositions which are suitable for the production of opaque cover coats and which do not contain fluorine and have a high boron content.
SUMMARY OF THEI NVENTION
o Fluorine-free frit compositions having a high content of boron oxide and a relatively low amount of titanium oxide are provided. A small amount of cobalt oxide is included in a preferred embodiment. These compositions are suitable for the preparation of enamel cover coats and are useful in both the dry and wet methods of application of frits. In particular, the frits ~re suitable for use in the electrostatic method of frit application on steel substrates. The sompositions of the invention are particularly suitable in "two coat-one fire"
applications. The enamel produced from the frit of the invent;on is characterized in its virtual freedom from pitting, relatively high acid resistance and exceptional color stability.
BACKGROUND OF THE INVENTION
Fluorine has long been recognized and used as a fluxing component in the manufacture of ena~el frits. In addition, traditional raw materials for the preparation of frits generally contain fluorine as a flux. Alkali and alkaline ; earth metal cations are routinely introduced as fluorides.
Recently, however, it has been recognized that fluorine : 30 emissions have an adverse effect on the ecology and regulations relative to its disposal have been promulgated and enforced.
~; Development of fluorine-free compositions have therefore been an objective of enamel and of frit producers and the present invention represents an advance in this technology.
3 505 5q~WR0811 ~ .
~ ~ , ::
.
ENAMEL COMPOSITIONS
CROSS-REFERENCE TO RELATED AppLIcA-rIoN
This application is a Continuation-in-Part of U.S.
Application Serial Number 07/490,215, filed March 8, 1990.
Field of the Invention The present invention relates to enamel compositions which are suitable for the production of opaque cover coats and which do not contain fluorine and have a high boron content.
SUMMARY OF THEI NVENTION
o Fluorine-free frit compositions having a high content of boron oxide and a relatively low amount of titanium oxide are provided. A small amount of cobalt oxide is included in a preferred embodiment. These compositions are suitable for the preparation of enamel cover coats and are useful in both the dry and wet methods of application of frits. In particular, the frits ~re suitable for use in the electrostatic method of frit application on steel substrates. The sompositions of the invention are particularly suitable in "two coat-one fire"
applications. The enamel produced from the frit of the invent;on is characterized in its virtual freedom from pitting, relatively high acid resistance and exceptional color stability.
BACKGROUND OF THE INVENTION
Fluorine has long been recognized and used as a fluxing component in the manufacture of ena~el frits. In addition, traditional raw materials for the preparation of frits generally contain fluorine as a flux. Alkali and alkaline ; earth metal cations are routinely introduced as fluorides.
Recently, however, it has been recognized that fluorine : 30 emissions have an adverse effect on the ecology and regulations relative to its disposal have been promulgated and enforced.
~; Development of fluorine-free compositions have therefore been an objective of enamel and of frit producers and the present invention represents an advance in this technology.
3 505 5q~WR0811 ~ .
~ ~ , ::
.
Enamel compositions containing titanium oxide and boron are known. For instance, in U.S. Patent 4,469,798 there is disclosed an enamel frit which contains 15 to 20% B203 and 10 to 17% TiO2. While the composition contains no lead and is 5 thus described as ;nvolv;ng no ecolog;cal problems, it is noted to require 2 to 10% of fluorine. Fluorine is said to function in agitating the frit and in keeping its acidity and is -regarded there as an essential component of the composition. ~-U.S. Patent 3,216,847 discloses a frit composition having o high contents of boron oxide and titanium oxide. The disclosure is silent in regard to the presence of fluorine and no cobalt oxide is noted as a necessary component.
U.S. Patent 3,017,279 also discloses a frit composition having high contents of boron oxide and titanium oxide. While the reference discloses that fluorine is an optional component, all of the examples are directed to the preparation of fluor~ne-containing frits. Therefore, the examples of this reference are consistent with the previous statement that fluorine-free frits are not readily available.
U.S. Patent 4,361,654 is directed to the preparation of fluorine-free frits which are suitable as ground coats for sheet iron. This reference does not suggest the use of the fluorine-free frits for the production of cover coats and the examples demonstrate that the fluorine-free frits would not be suitable for this purpose. Even though a broad range of titaniu~ oxide is set forth, the highest amount used in any of the examples is 4.1X by weight. At this low amount the titanium oxide remains dissolved in the frit. Only when the amount increases to about 8 to 10% does the titanium oxide begin to crystallize out in the resulting frit such that the frit starts to become opaque. As this amount increases to in excess of 15%, the frit becomes completely opaque and attains the bright white or almond appearance which is necessary for a cover coat. The presence of 4.1X by weight or less in the examples of U.S. Patent 4,361,654 is consistent ~ith the use of Mo-3400-CIP
:
.
.. . .. . . . .... .
- 2~37~
U.S. Patent 3,017,279 also discloses a frit composition having high contents of boron oxide and titanium oxide. While the reference discloses that fluorine is an optional component, all of the examples are directed to the preparation of fluor~ne-containing frits. Therefore, the examples of this reference are consistent with the previous statement that fluorine-free frits are not readily available.
U.S. Patent 4,361,654 is directed to the preparation of fluorine-free frits which are suitable as ground coats for sheet iron. This reference does not suggest the use of the fluorine-free frits for the production of cover coats and the examples demonstrate that the fluorine-free frits would not be suitable for this purpose. Even though a broad range of titaniu~ oxide is set forth, the highest amount used in any of the examples is 4.1X by weight. At this low amount the titanium oxide remains dissolved in the frit. Only when the amount increases to about 8 to 10% does the titanium oxide begin to crystallize out in the resulting frit such that the frit starts to become opaque. As this amount increases to in excess of 15%, the frit becomes completely opaque and attains the bright white or almond appearance which is necessary for a cover coat. The presence of 4.1X by weight or less in the examples of U.S. Patent 4,361,654 is consistent ~ith the use of Mo-3400-CIP
:
.
.. . .. . . . .... .
- 2~37~
the fluorine-free frits as ground coats as opposed to cover coats.
It is an objective of the present invention to provide a fluorine free frit which ;s suitable for the preparation of an .s op~que, white- or almond-colored, acid resistant enamel cover coat.
It is a further objective of the invention to provide an ecologically compatible frit composition having a desirable set of properties.
DETAILED DESCRIPTION OF THE INVENTION
The frit of the present invention is characterized in that (i) it flows to form a smooth and uniform coating at a sufficiently low temperature, (ii) the coefficient of thermal expansion of the resulting enamel is sufficiently low so as to be compatible with most ferrous substrates, ~iii) the resulting enamel is acid resistant, and (iv) upon the firing process, it partially devitrifies and becomes opaque.
In terms of 1ts content, expressed as weight percent on -the basis of its oxides, the frit of the present invention contains Oxide Wt %
. SiO2 40 - 45 TiO2 15 - 18 Na20 5 - 10 Al 23 1 - 4 ~ .
: Li20 0.25 - 1.0 In a preferred embodiment, the frit also contains CoO 0.02 - 0.1 optionally, the composition may further contain, the amounts noted as percent by weight, Mo-3400-CIP
. .. .. -~:
~ .
~Q~7~7~ `
It is an objective of the present invention to provide a fluorine free frit which ;s suitable for the preparation of an .s op~que, white- or almond-colored, acid resistant enamel cover coat.
It is a further objective of the invention to provide an ecologically compatible frit composition having a desirable set of properties.
DETAILED DESCRIPTION OF THE INVENTION
The frit of the present invention is characterized in that (i) it flows to form a smooth and uniform coating at a sufficiently low temperature, (ii) the coefficient of thermal expansion of the resulting enamel is sufficiently low so as to be compatible with most ferrous substrates, ~iii) the resulting enamel is acid resistant, and (iv) upon the firing process, it partially devitrifies and becomes opaque.
In terms of 1ts content, expressed as weight percent on -the basis of its oxides, the frit of the present invention contains Oxide Wt %
. SiO2 40 - 45 TiO2 15 - 18 Na20 5 - 10 Al 23 1 - 4 ~ .
: Li20 0.25 - 1.0 In a preferred embodiment, the frit also contains CoO 0.02 - 0.1 optionally, the composition may further contain, the amounts noted as percent by weight, Mo-3400-CIP
. .. .. -~:
~ .
~Q~7~7~ `
MgO O - 1.0 ZnO O - 1.0 -P205 o - 3.0 Nb205 0 - 0.1 NiO - 0-5 Cr203 0 - 0.1 ; .
MnO2 ~ 1 Fe203 0 - 1 . O
- The frit is fluorine-free and has a relatively high -.
lo content of boron oxide and a relatively low content of titanium oxide. A small amount of cobalt oxide is i~cluded in a -preferred embodiment. In addition, the frit is characterized in the absence of barium oxide therefrom. :
While the frit of the invention is suitable for preparing enamel cover coats by using either a dry or a wet process, it -has been surprisingly found that the composition of the invent~on is particularly suitable for use in the dry method, preferably the electrostatic meth~d, for applying frits. The resulting enamel cover coat was surprisingly and unexpectedly 20. found to be uniform, color stable and resistant to chemical attack by acids. This is particularly surprising in view of the recognition in the industry that the dry method, and more particularly the electrostatic method, is generally less ~`
forgiving, i.e., has a narrower margin for error, than other ;
25 methods of frit application.
The electrostatic method for applying frits to a metallic substrate is well known in the art and described in U.S. Patent ; 3,928,668, the disclosure of which is incorporated herein by ~-reference. In accordance with this method, a frit, optionally 30~ having first been coated with a suitable agent to impart a high ` resistivity, is electrostatically deposited by spraying it uniformly over a substrate and fired to form an enamel. It has long been recognized that the method, although offering several processing advantages and resulting in an excellent enamel s coating, is less~forgiving than the known wet method of Mo-3400-ClP
2Q3~3 7~
application. This sensitivity to small variations in the process may lead to poor quality in the resulting enamel. It was therefore surprising and unexpected to find that the composition of the present invention is very suitable for application by electrostatic deposition and that process variations do not result in enamels of poor quality.
In accordance with the present invention the frit may be directly applied to a metal substrate or it may be applied to a ground coat. In a preferred embodiment the frit is applied to the ground coat before the ground coat is fired and then both coats are fired. This method is referred to as "two coat, one fire" process. Also, in accordance with the present invention it is not necessary to blend the frit with other additives prior to applying it to a substrate using the wet or dry processes.
A high boron content in a frit composition is generally associated with the poor acid resistance of the resulting enamels. Accordingly, the good acid resistance of the enamels of the present invention is also surprising and unexpected.
Specifically, while compositions containing about 20 percent boron oxide are rated, at best, B in accordance with the PEI -Porcelain Enamel Institute - acid resistance test, the composition of the present invention, although containing a high level boron, is consistently rated at least A on the same scale.
In accsrdance with the method of application of the composition of the present invention, the frit is applied on the substrate at a rate of approximately 30 grams per square foot. This rate of application results upon firing in an enamel having a thickness of about 5 mils.
PROCEDURE OUTLINE
The following is a description of the procedure which was used for preparing a composition within the scope of the invention. The raw materials were weighed (the raw material Mo-3400-CIP
:
` 2~7~7~
formula is set forth in the table below), dry blended and charged into a glass melting furnace.
Material Weight Silicon Dioxide 1480.0 Sodium Borate (Na2B4O7) 623.0 Zinc Oxide 12.5 Potass;um Nitrate 135.0 Boric Acid 17.9 Lithium Carbonate 41.6 Titanium Dioxide 611.0 Potassium Carbonate 219.0 .
Aluminum Oxide 113.0 Sodium Tripolyphosphate 38.6 Magnesium Oxide 17.0 Sodium Borate Pentahydrate (Na2B4O7.5H2O) 674.0 Cobalt Hydrate/Silicon Dioxide 18.6 Compositions within the scope of the invention were melted in a laboratory scale gas-air fired rotary smelter for about 12-18 minutes and at a temperature of 2000 to 2500F. The resulting molten glass was poured into water to produce the frit. Additionally, frit compositions were melted in production scale continuous gas-oxygen fired smelters at a temperature of about 2200-2400F. The production smelted material was made into frit form by passing it through water-cooled rollers. ;
The fritted material was comminuted using conventional means. Typically, 80-85 percent by weight of the thus comminuted frit has an average particle size of less than 45 micrometers (325 mesh).
3Q The thus produced frit was used to provide an enamel cover coat to steel samples ùsing conventional wet and dry application techniques.
Steel coupons (20 gauge extra low carbon cleaned steel) were used as the coated substrate. Frit in accordance with the invention was applied and the sample was fired at a temperature .
~ Mo-3400-CIP
3 ~ ~
of 1350 to 1600-F. Holding times rang;ng from 3 to 10 minutes were used to simulate commercial firing conditions. Also, a high humidity condition was induced to simulate a worst case condition in terms of the resulting surface appearance.
Standard evaluation tests were performed on the fired samples, including the Porcelain Enamel Institute (PEI3 acid resistance test, color stability under varying firing conditions and the loaded beam stress test to determine the compressive stress present in the fired coating. In all cases, the surface quality of the enamels prepared from the frit of the invention exceeded that of currently available commercial products.
Modifications and variations to the above described invention are possible and might occur to those skilled in the art in view of the present disclosure. It is however to be understood that such changes are within the scope of the invention as defined by the following clai~s. -Mo-3400-CIP
.
MnO2 ~ 1 Fe203 0 - 1 . O
- The frit is fluorine-free and has a relatively high -.
lo content of boron oxide and a relatively low content of titanium oxide. A small amount of cobalt oxide is i~cluded in a -preferred embodiment. In addition, the frit is characterized in the absence of barium oxide therefrom. :
While the frit of the invention is suitable for preparing enamel cover coats by using either a dry or a wet process, it -has been surprisingly found that the composition of the invent~on is particularly suitable for use in the dry method, preferably the electrostatic meth~d, for applying frits. The resulting enamel cover coat was surprisingly and unexpectedly 20. found to be uniform, color stable and resistant to chemical attack by acids. This is particularly surprising in view of the recognition in the industry that the dry method, and more particularly the electrostatic method, is generally less ~`
forgiving, i.e., has a narrower margin for error, than other ;
25 methods of frit application.
The electrostatic method for applying frits to a metallic substrate is well known in the art and described in U.S. Patent ; 3,928,668, the disclosure of which is incorporated herein by ~-reference. In accordance with this method, a frit, optionally 30~ having first been coated with a suitable agent to impart a high ` resistivity, is electrostatically deposited by spraying it uniformly over a substrate and fired to form an enamel. It has long been recognized that the method, although offering several processing advantages and resulting in an excellent enamel s coating, is less~forgiving than the known wet method of Mo-3400-ClP
2Q3~3 7~
application. This sensitivity to small variations in the process may lead to poor quality in the resulting enamel. It was therefore surprising and unexpected to find that the composition of the present invention is very suitable for application by electrostatic deposition and that process variations do not result in enamels of poor quality.
In accordance with the present invention the frit may be directly applied to a metal substrate or it may be applied to a ground coat. In a preferred embodiment the frit is applied to the ground coat before the ground coat is fired and then both coats are fired. This method is referred to as "two coat, one fire" process. Also, in accordance with the present invention it is not necessary to blend the frit with other additives prior to applying it to a substrate using the wet or dry processes.
A high boron content in a frit composition is generally associated with the poor acid resistance of the resulting enamels. Accordingly, the good acid resistance of the enamels of the present invention is also surprising and unexpected.
Specifically, while compositions containing about 20 percent boron oxide are rated, at best, B in accordance with the PEI -Porcelain Enamel Institute - acid resistance test, the composition of the present invention, although containing a high level boron, is consistently rated at least A on the same scale.
In accsrdance with the method of application of the composition of the present invention, the frit is applied on the substrate at a rate of approximately 30 grams per square foot. This rate of application results upon firing in an enamel having a thickness of about 5 mils.
PROCEDURE OUTLINE
The following is a description of the procedure which was used for preparing a composition within the scope of the invention. The raw materials were weighed (the raw material Mo-3400-CIP
:
` 2~7~7~
formula is set forth in the table below), dry blended and charged into a glass melting furnace.
Material Weight Silicon Dioxide 1480.0 Sodium Borate (Na2B4O7) 623.0 Zinc Oxide 12.5 Potass;um Nitrate 135.0 Boric Acid 17.9 Lithium Carbonate 41.6 Titanium Dioxide 611.0 Potassium Carbonate 219.0 .
Aluminum Oxide 113.0 Sodium Tripolyphosphate 38.6 Magnesium Oxide 17.0 Sodium Borate Pentahydrate (Na2B4O7.5H2O) 674.0 Cobalt Hydrate/Silicon Dioxide 18.6 Compositions within the scope of the invention were melted in a laboratory scale gas-air fired rotary smelter for about 12-18 minutes and at a temperature of 2000 to 2500F. The resulting molten glass was poured into water to produce the frit. Additionally, frit compositions were melted in production scale continuous gas-oxygen fired smelters at a temperature of about 2200-2400F. The production smelted material was made into frit form by passing it through water-cooled rollers. ;
The fritted material was comminuted using conventional means. Typically, 80-85 percent by weight of the thus comminuted frit has an average particle size of less than 45 micrometers (325 mesh).
3Q The thus produced frit was used to provide an enamel cover coat to steel samples ùsing conventional wet and dry application techniques.
Steel coupons (20 gauge extra low carbon cleaned steel) were used as the coated substrate. Frit in accordance with the invention was applied and the sample was fired at a temperature .
~ Mo-3400-CIP
3 ~ ~
of 1350 to 1600-F. Holding times rang;ng from 3 to 10 minutes were used to simulate commercial firing conditions. Also, a high humidity condition was induced to simulate a worst case condition in terms of the resulting surface appearance.
Standard evaluation tests were performed on the fired samples, including the Porcelain Enamel Institute (PEI3 acid resistance test, color stability under varying firing conditions and the loaded beam stress test to determine the compressive stress present in the fired coating. In all cases, the surface quality of the enamels prepared from the frit of the invention exceeded that of currently available commercial products.
Modifications and variations to the above described invention are possible and might occur to those skilled in the art in view of the present disclosure. It is however to be understood that such changes are within the scope of the invention as defined by the following clai~s. -Mo-3400-CIP
.
Claims (20)
1. A frit composition which is suitable for preparing an opaque, color stable, white- or almond-colored, acid resistant enamel cover coat and comprises the following oxides on a weight percent basis:
and which does not contain fluorine or barium oxide.
and which does not contain fluorine or barium oxide.
2. The composition of Claim 1 which further comprises a positive amount of up to about 1.0 percent by weight of at least one member selected from the group consisting of MgO, ZnO, Fe2O3 and MnO2.
3. The composition of Claim 1 which further comprises a positive amount of up to about 0.1 percent by weight of at least one member selected from the group consisting of Nb2O5 and Cr2O3.
4. The composition of Claim 1 which further comprises a positive amount of up to about 0.5 percent by weight of NiO.
5. The composition of Claim 1 which further comprises a positive amount of up to about 3.0 percent by weight of P2O5.
6. The composition of Claim 2 which further comprises a positive amount of up to about 0.1 percent by weight of at least one member selected from the group consisting of Nb2O5 and Cr2O3.
7. The composition of Claim 6 which further comprises a positive amount of up to about 0.5 percent by weight of NiO.
8. The composition of Claim 7 which further comprises a positive amount of up to about 3.0 percent by weight of P2O5.
9. The composition of Claim 4 which further comprises a positive amount of up to about 1.0 percent by weight of Fe2O3.
10. The composition of Claim 1 which comprises the following oxides:
11. In the dry process of applying frit to a substrate by electrostatic deposition, the improvement which comprises using a frit composition which is suitable for preparing an opaque, color stable, white- or almond-colored, acid resistant enamel cover coat and comprises the following oxides on a weight percent basis:
and which does not contain fluorine or barium oxide.
and which does not contain fluorine or barium oxide.
12. The process of Claim 11 wherein said frit composition further comprises a positive amount of up to about 1.0 percent by weight of at least one member selected from the group consisting of MgO, ZnO, Fe2O3 and MnO2.
13. The process of Claim 11 wherein said frit composition further comprises a positive amount of up to about 0.1 percent by weight of at least one member selected from the group consisting of Nb2O5 and Cr2O3.
14. The process of Claim 11 wherein said frit composition further comprises a positive amount of up to about 0.5 percent by weight of NiO.
15. The process of Claim 11 wherein said frit composition further comprises a positive amount of up to about 3.0 percent by weight of P2O5.
16. The process of Claim 12 wherein said frit composition further comprises a positive amount of up to about 0.1 percent by weight of at least one member selected from the group consisting of Nb2O5 and Cr2O3.
17. The process of Claim 16 wherein said frit composition further comprises a positive amount of up to about 0.5 percent by weight of NiO.
18. The process of Claim 17 wherein said frit composition further comprises a positive amount of up to about 3.0 percent by weight of P2O5.
19. The process of Claim 14 wherein said frit composition further comprises a positive amount of up to about 1.0 percent by weight of Fe2O3.
20. The process of Claim 11 wherein said frit composition comprises the following oxides:
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49021590A | 1990-03-08 | 1990-03-08 | |
| US07/490,215 | 1990-03-08 | ||
| US64584791A | 1991-01-25 | 1991-01-25 | |
| US07/645,847 | 1991-01-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2037372A1 true CA2037372A1 (en) | 1991-09-09 |
Family
ID=27049995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2037372 Abandoned CA2037372A1 (en) | 1990-03-08 | 1991-02-28 | Enamel compositions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2037372A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0631995A1 (en) | 1993-06-24 | 1995-01-04 | Dentsply GmbH | Dental prosthesis |
| RU2614763C1 (en) * | 2016-02-09 | 2017-03-29 | Юлия Алексеевна Щепочкина | Enamel coating |
| CN108467201A (en) * | 2018-05-16 | 2018-08-31 | 苏州工业园区职业技术学院 | A kind of free-floride titanium enamel and preparation method thereof |
-
1991
- 1991-02-28 CA CA 2037372 patent/CA2037372A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0631995A1 (en) | 1993-06-24 | 1995-01-04 | Dentsply GmbH | Dental prosthesis |
| US5849068A (en) * | 1993-06-24 | 1998-12-15 | Dentsply G.M.B.H. | Dental prosthesis |
| US6126732A (en) * | 1993-06-24 | 2000-10-03 | Dentsply Detrey Gmbh | Dental prosthesis |
| RU2614763C1 (en) * | 2016-02-09 | 2017-03-29 | Юлия Алексеевна Щепочкина | Enamel coating |
| CN108467201A (en) * | 2018-05-16 | 2018-08-31 | 苏州工业园区职业技术学院 | A kind of free-floride titanium enamel and preparation method thereof |
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Legal Events
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