U.S. patent application number 11/688099 was filed with the patent office on 2007-10-04 for transparent glass ceramic plate that has an opaque, colored bottom coating over the entire surface or over part of the surface.
Invention is credited to Petra Grewer, Erich Rodek, Ulrich Schiffner, Wolfgang Schmidbauer, Klaus Schonberger, Friedrich Siebers.
Application Number | 20070232476 11/688099 |
Document ID | / |
Family ID | 37027816 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070232476 |
Kind Code |
A1 |
Siebers; Friedrich ; et
al. |
October 4, 2007 |
TRANSPARENT GLASS CERAMIC PLATE THAT HAS AN OPAQUE, COLORED BOTTOM
COATING OVER THE ENTIRE SURFACE OR OVER PART OF THE SURFACE
Abstract
A transparent, colorless lithium-aluminosilicate glass ceramic
plate with high-quartz mixed crystals as the prevailing crystal
phase, which is provided on one side with an opaque, colored,
temperature-stable coating over the entire surface or over the
entire surface to a large extent, is described, which has a content
of Nd.sub.2O.sub.3 of 40 to 4000 ppm, a Yellowness Index of less
than 10% with a 4 mm glass (ceramic) layer thickness, and a
variegation of colors of the glass or the glass ceramic in the
CIELAB color system of C* of less than 5. The glass ceramic plate
preferably has a composition (in % by weight based on oxide) of:
Li.sub.2O 3.0-4.5, Na.sub.2O 0-1.5, K.sub.2O 0-1.5,
.SIGMA.Na.sub.2O+K.sub.2O 0.2-2.0, MgO 0-2.0, CaO 0-1.5, SrO 0-1.5,
BaO 0-2.5, ZnO 0-2.5, B.sub.2O.sub.3 0-1.0, Al.sub.2O.sub.3 19-25,
SiO.sub.2 55-69, TiO.sub.2 1-3, ZrO.sub.2 1-2.5, SnO.sub.2 0-0.4,
.SIGMA.SnO.sub.2+TiO.sub.2<3, P.sub.2O.sub.5 0-3.0,
Nd.sub.2O.sub.3 0.01-0.4, CoO 0.0-0.004
Inventors: |
Siebers; Friedrich;
(Nierstein, DE) ; Schiffner; Ulrich; (Mainz,
DE) ; Schmidbauer; Wolfgang; (Mainz, DE) ;
Schonberger; Klaus; (Mainz, DE) ; Grewer; Petra;
(Wiesbaden, DE) ; Rodek; Erich; (Mainz,
DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
37027816 |
Appl. No.: |
11/688099 |
Filed: |
March 19, 2007 |
Current U.S.
Class: |
501/4 ;
501/7 |
Current CPC
Class: |
C03C 3/095 20130101;
C03C 10/0054 20130101; C03C 10/0027 20130101; C03C 10/0045
20130101 |
Class at
Publication: |
501/004 ;
501/007 |
International
Class: |
C03C 10/14 20060101
C03C010/14; C03C 10/12 20060101 C03C010/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 2006 |
EP |
06 005 598.5 |
Claims
1. Transparent, colorless lithium-aluminosilicate glass ceramic
plate with high-quartz mixed crystals as the prevailing crystal
phase, which is provided on one side with an opaque, colored,
temperature-stable coating over the entire surface or over the
entire surface to a large extent, characterized by a content of
Nd.sub.2O.sub.3 of 40 to 4000 ppm, a Yellowness Index of less than
10% with a 4 mm thickness, and a variegation of colors of the glass
ceramic in the CIELAB color system of C* of less than 5.
2. Glass ceramic plate according to claim 1, characterized by an
additional content of 0-50 ppm of CoO.
3. Glass ceramic plate according to claim 1, characterized by a
composition (in % by weight based on oxide) of: TABLE-US-00007
Li.sub.2O 3.0-4.5 Na.sub.2O 0-1.5 K.sub.2O 0-1.5 .SIGMA.Na.sub.2O +
K.sub.2O 0.2-2.0 MgO 0-2.0 CaO 0-1.5 SrO 0-1.5 BaO 0-2.5 ZnO 0-2.5
B.sub.2O.sub.3 0-1.0 Al.sub.2O.sub.3 19-25 SiO.sub.2 55-69
TiO.sub.2 1-3 ZrO.sub.2 1-2.5 SnO.sub.2 0-0.4 .SIGMA.SnO.sub.2 +
TiO.sub.2 <3 P.sub.2O.sub.5 0-3.0 Nd.sub.2O.sub.3 0.01-0.4 CoO
0.0-0.004
optionally with the additions of chemical refining agents such as
As.sub.2O.sub.3, Sb.sub.2O.sub.3, and CeO.sub.2 and refining
additives, such as sulfate compounds, chloride compounds, and
fluoride compounds in total contents of up to 2.0% by weight.
4. Glass ceramic plate according to claim 3, characterized by a
content (in % by weight based on oxide) of: TABLE-US-00008
Li.sub.2O 3.2-4.3 Na.sub.2O 0.2-1.0 K.sub.2O 0-0.8 .SIGMA.Na.sub.2O
+ K.sub.2O 0.3-1.5 MgO 0.1-1.5 CaO 0-1.0 SrO 0-1.0 BaO 0-2.5 ZnO
0-2.0 Al.sub.2O.sub.3 19-24 SiO.sub.2 60-68 TiO.sub.2 1.0-2.7
ZrO.sub.2 1.2-2.2 SnO.sub.2 0-0.3 .SIGMA.SnO.sub.2 + TiO.sub.2
<2.7 P.sub.2O.sub.5 0-3.0 Nd.sub.2O.sub.3 0.02-0.3 CoO
0.0-0.003
optionally with the additions of chemical refining agents such as
As.sub.2O.sub.3, Sb.sub.2O.sub.3, and CeO.sub.2 and refining
additives such as sulfate compounds, chloride compounds, and
fluoride compounds in total amounts of up to 1.5% by weight.
5. Glass ceramic plate according to claim 3, characterized in that
the content of ZrO.sub.2+0.87 (TiO.sub.2+SnO.sub.2) is 3.65 to 4.3%
by weight.
6. Glass ceramic plate according to claim 1, characterized by a
content of less than 2.5% by weight of TiO.sub.2, less than 2000
ppm of Nd.sub.2O.sub.3, less than 400 ppm, preferably less than 210
ppm of Fe.sub.2O.sub.3, a light transmittance of more than 80%, in
particular more than 85%, and a Yellowness Index of less than 7, in
each case with a 4 mm layer thickness as well as a variegation of
colors of C* of less than 3.5 in the CIELAB color system.
Description
[0001] The invention relates to a transparent glass ceramic plate
with high-quartz mixed crystals as the prevailing crystal phase,
which is exposed to operationally high thermal stresses and which
has an opaque, colored, high-temperature-stable bottom coating over
the entire surface or over part of the surface.
[0002] In terms of this invention, glass ceramic plates are to be
defined as not only flat, smooth plates, but also plates that are
deformed three-dimensionally, such as, e.g., beveled, angled or
curved plates. In this case, the plates can be designed rectangular
or round or can also have another shape. Such glass ceramic plates
have a very low thermal expansion coefficient in the temperature
range between room temperature up to 700.degree. C. of usually
.alpha..sub.20/700<1.510.sup.-6/K and thus high temperature
resistance and temperature gradient strength. They are used in
transparent form, e.g., as fire protection glass, fireplace door
windows and cooking surfaces.
[0003] Stove tops with a glass ceramic plate as a cooking surface
are current prior art.
[0004] To prevent an unsettling view of the technical elements
under the glass ceramic cooking surface and to avoid the shielding
action caused by radiating heating elements, the glass ceramic
cooking surfaces are reduced in their light transmission to values
of about 0.5 to 10%. This can take place, on the one hand, by
additions of coloring elements by absorption, as is described in,
for example, EP 220333. These glass ceramic cooking surfaces then
appear black when viewed from above and red-violet or orange-brown
when looking through depending on the coloring elements that are
used.
[0005] In glass ceramic cooking surfaces with keatite crystals as
the prevailing crystal phase, the required light transmission with
light scattering on the enlarged crystallites can be adjusted, as
is described in EP 1 170 264. A basic drawback of these two types
of glass ceramic cooking surfaces exists in their limited display
capacity. The tinting of the glass ceramic cooking surface with
absorbing elements results in that displays are possible only with
certain colors, in most cases with the color red. The reduction of
the light transmission by light scattering results in that the
displays no longer appear sharp and produce unsettling haloes.
[0006] Another application of the glass ceramic panes exists in the
use as, e.g., fireplace door windows. For this purpose, the panes
must be transparent. For manufacturing purposes, it is advantageous
if panes of the same composition could be used for these two
applications.
[0007] A comparatively new technical approach for the production of
cooking surfaces consists in making transparent glass ceramic
plates optically non-transparent by an opaque, colored bottom
coating. The bottom coating is optionally partially interrupted by
providing optically transparent areas for displays, e.g., LED or
LCD displays of residual heat in the cooking zones. Also, color or
black-white screen displays, e.g., for showing cooking recipes or
for interactive functions (Internet, integration with other
household appliances, control electronics) can be integrated under
the optically transparent areas.
[0008] Transparent, non-colored stove tops, which are provided with
a bottom coating, are known from, e.g., U.S. Pat. No. 6,914,223 B2,
US 2005/0129959 A1 or U.S. Pat. No. 6,660,989 B2. The type and
structure of the bottom coating can be designed differently in the
colder and hotter areas, e.g., in the cooking zones of the cooking
surfaces.
[0009] As paints that meet the specifications for these bottom
coatings, in particular luster paints, organic-based paints,
glass-flux-based decorative paints with coloring pigments and
colored or pigmented sol-gel layers are mentioned. As pigments,
conventional inorganic pigments, luster pigments, metal effect
pigments or pearlescent interference pigments and various mixtures
of these pigments are used.
[0010] So that the color of the bottom coating is not altered by
the transparent glass ceramic plate, it is advantageous if the
latter has a low inherent color. Since the irradiating light passes
through the glass ceramic plate before it falls on the colored
coating to be partially absorbed and reflected on the latter,
before it then passes back again through the glass ceramic plate
and reaches the observer, a weak inherent color of the transparent
glass ceramic plate also has a disruptive effect. The advantages of
a transparent glass ceramic plate with low inherent color are found
in the prior art.
[0011] Thus, e.g., U.S. Pat. No. 6,660,980 B2 describes the use of
a transparent glass ceramic as a substrate for the bottom coating.
The usual slightly brownish-yellow inherent coloring of the latter
and other glass ceramic plates used was perforce previously
accepted.
[0012] In Column 6, paragraph 3, U.S. Pat. No. 6,914,223 B2
describes how a new color shade is set by superposition of the
colors of the bottom coating with the brownish-yellow inherent
coloring of the glass ceramic plate. It is disadvantageous that the
recognizable inherent color of the transparent glass ceramic plate
depends on the thickness thereof. In addition, certain pure color
shades, e.g., white or silver-metallic, cannot be produced for the
observer without an unsettling brown-yellow color hue. In the
development of a color palette of various colored bottom coatings,
it is necessary always to consider the inherent color of the
transparent glass ceramic plates. For the observer, this inherent
color is, however, as explained, dependent on the thickness of the
glass ceramic plates and can also vary by process-induced
fluctuations (raw material contamination, melt conditions,
glazing). For the above-mentioned reasons, an effort is therefore
to be made to set the inherent color in the transparent glass
ceramic plate to as low a value as possible.
[0013] The inherent color of transparent glass ceramic plates can
have various causes. Also, the use of the refining agent
Sb.sub.2O.sub.3 results in a low inherent color. The described
brownish-yellow inherent coloring of the transparent glass ceramics
is based on electronic transitions to color complexes that absorb
in the area of the visible light and on which the component--the Ti
ion--that is necessary for the nucleation is involved. The most
frequently absorbing color complex is the formation of adjacent Fe
and Ti ions, between which electronic charge-transfer transitions
take place. The formation of these adjacent complexes takes place
as early as during cooling of the starting glass and in particular
during later glazing of the glass ceramics. By preferred
stratification of the ions involved in the charge transfer during
glazing, the inherent color is thus quite considerably enhanced
compared to the starting glass.
[0014] In the production of glass ceramic plates with the addition
of SnO.sub.2 as a nucleating agent or refining agent, it has been
shown that with glazing, an additional disruptive color complex
occurs. This color complex is based on Sn/Ti color complexes, which
also absorb in the short- to middle-wave portion of the visible
spectrum. In the starting glasses, this color complex is less well
formed; after glazing, it results in a very disruptive yellow-brown
coloring in the transparent glass ceramic.
[0015] For transparent glass ceramics without colored coating,
various approaches are known to reduce the disruptive inherent
color that is based on the Fe/Ti color complex. One approach is the
reduction of the iron content that is present as a contaminant.
[0016] The reduction of the Fe content is a measure that is
economically usable only to a certain extent, however. A certain
amount of Fe.sub.2O.sub.3 always develops through the industrially
available raw materials of the batch for the production and
homogenization of the batch. Based on the costs for extremely pure
raw materials and for special plant design measures, it is
economically no longer justifiable to reduce the Fe.sub.2O.sub.3
content below about 50 ppm in transparent glass ceramics. The
Fe.sub.2O.sub.3 content is usually on the order of magnitude of
about 150 to 500 ppm.
[0017] U.S. Pat. No. 4,438,210 describes approaches for reducing
the Fe/Ti color complex. Here, transparent glass ceramics with low
inherent color are obtained, which acquire 2-6% by weight of
TiO.sub.2 and 0-2% by weight of ZrO.sub.2 as a nucleating agent and
up to about 0.1% by weight of Fe.sub.2O.sub.3 as a contaminant
because the component MgO is essentially omitted.
[0018] The replacement of the nucleating agent TiO.sub.2 is
described in JP 03-23237 A. These glass ceramics forego the
addition of TiO.sub.2 as a nucleating agent and are based on mixed
nucleation by ZrO.sub.2/SnO.sub.2. The SnO.sub.2 contents that are
necessary for this purpose are more than 1% by weight. In the case
of these high SnO.sub.2 contents, however, the devitrification
resistance of the glass deteriorates in the area of shaping in
viscosities around the processing temperature V.sub.A of 10.sup.4
dpas. During shaping, which is carried out in glass ceramic plates
usually with an upper roller and a lower roller, disruptive Sn--
and/or Zr-containing crystal phases crystallize out. It thus
results in an unreliable reduction of the resistance of the glass
plates and the glass ceramic plates that are produced
therefrom.
[0019] To avoid a disruptive light scattering (turbidity) of the
transparent glass ceramic plate, however, certain minimum contents
of the nucleating agents ZrO.sub.2, TiO.sub.2 and optionally
SnO.sub.2 are necessary. Thus, it is ensured that even in the short
glazing times that are desired for manufacturing technology,
sufficient nuclei are formed, and the growing high-quartz mixed
crystals remain small enough not to result in a disruptive light
scattering. The light scattering can be determined visually on
glass ceramic plates or quantitatively by measuring the turbidity
(English: haze) according to ASTM D 1003. Since the contents of the
nucleating agents ZrO.sub.2 and SnO.sub.2 are limited because of
the devitrification during shaping, a minimum content of the
nucleating agent TiO.sub.2 is necessary in the current prior art to
ensure the devitrification resistance during shaping of glass
plates.
[0020] From the glass technology, it is also known to neutralize an
undesirable color hue, which is produced by a contamination of the
gas with a coloring element, by the addition of a coloring element
with a complementary color. The addition of MnO.sub.2 ("gaffer
soap") for elimination of weak coloration caused by iron has been
known since time immemorial. Also, the neutralization of the amber
coloration produced by titanium and iron by neodymium oxide is
known from U.S. Pat. No. 4,093,468. By the neutralization (staining
over) of the disruptive color hue, it is achieved that the
disruptive inherent color is altered in the direction of a neutral
color shade. Neutral color shades, e.g., weak gray shades, thus are
visually less obvious and disruptive. The color of the coating when
looking through the transparent glass ceramic plate is not altered
in color but rather is superimposed in a hardly noticeable way by a
light gray hue. Since the existing absorption bands are neutralized
by complementary absorption bands of the staining agent, a reduced
light transmission is produced overall.
[0021] Since the use of arsenic as a refining agent is always less
tolerated for known reasons, it is plained to an increasing extent
with other refining agents, in particular antimony oxide and tin
oxide, but also cerium dioxide. These refining agents or glass
additives add additional color hues to the glass ceramic, which
also have to be neutralized. In this case, however, it should not
come to the point where the transmission of the glass ceramic is so
greatly impaired that the neutral coloration that is produced
produces a gray coloration.
[0022] Another problem develops in the recycling of the glass
ceramic. As is generally known, scrap glass, e.g., container glass,
such as bottles, glass containers, but also flat glass, such as
window glass, is collected to a great extent and recycled in the
form of cullets. If glass ceramic also finds its way into these
cullets, this results in problems in the melting tanks and in the
shaping process, since the glass ceramics from the
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2 glass system have higher
melting points and thus can have a very disruptive effect during
remelting of the lime-sodium glasses and the shaping thereof. The
danger exists because the high-melting
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2 glass does not form melted
remnants in the lime-sodium glasses. In the most advantageous case,
this results in visually recognizable remnants in the lime-sodium
glass products; in the most disadvantageous case, it can result in
Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2 melt remnants and in the
clogging of channels or nozzles in the shaping process and thus in
total failure during production of lime-sodium glasses.
[0023] Even now, cullets are frequently already being separated
before they are recycled by optical recognition methods after
sorting, e.g., brown glass, green glass, colorless glass. These
optical recognition methods separate the cullets based on their
different absorption bands. It would be desirable if the glass
ceramic cullets could also be recognized and separated in this
separation process, on the one hand, to protect the used-glass
tanks and, on the other hand, also to be able to recycle the glass
ceramic cullets.
[0024] The object is therefore to find a glass ceramic plate that
is coated over the entire surface or over part of the surface on
the back side and that does not have any of the disruptive color
shade distorting the colors of the coating on the back side and
that can be clearly identified in cullet sorting facilities with
optical cullet recognition.
[0025] This object is achieved by the glass ceramic plate that is
described in claim 1. Additional embodiments of the invention are
described in the subclaims.
[0026] A glass ceramic plate that is coated on the back side in the
lithium-aluminosilicate glass system with high-quartz mixed
crystals as a prevailing crystal phase was found, and said plate
has an Nd.sub.2O.sub.3 content of 40-4000 ppm, a Yellowness Index
of less than 10% with a 4 mm plate thickness and a variegation of
colors of the glass ceramic in the CIELAB color system of C* of
less than 5.
[0027] The measurement of the Yellow Index takes place with
standard illuminant C according to the ASTM Standard 1925/70 (77,
85). The variegation of colors (chromaticity) C* in the CIELAB
system is defined by C*= {square root over
(.alpha.*.sup.2+b*.sup.2)}, whereby a* and b* are the color
coordinates in this system. The color coordinates L*, a*, and b*
from the CIELAB system (or, in short, lab system) can be converted
in a known way into color coordinates x, y and brightness (light
transmission) Y of the CIE color system.
[0028] It was found that the neodymium addition especially readily
counteracts the color hues formed by Sb.sub.2O.sub.3 refining
additives and by SnTi color complexes, in addition to the color
hues formed by Fe/Ti color complexes.
[0029] Additions of CO in a total amount of up to 50 ppm,
preferably 0-40 ppm, in particular 0.1-40 ppm, in addition to the
Nd additive, allow the color point of the transparent color ceramic
plate to be set more precisely in the direction of the achromatic
point. The Nd additive by itself does not shift the color point
exactly in the direction of the achromatic point, such that this
slight correction may be advantageous. Additional fine corrections
of the color site can also be performed with other staining agents,
such as, e.g., Cr, Ni, V, Cu, Mn and Ce.
[0030] The transparent glass ceramic plate according to the
invention preferably has a composition in % by weight based on
oxide of: TABLE-US-00001 Li.sub.2O 3.0-4.5 Na.sub.2O 0-1.5 K.sub.2O
0-1.5 .SIGMA.Na.sub.2O + K.sub.2O 0.2-2.0 MgO 0-2.0 CaO 0-1.5 SrO
0-1.5 BaO 0-2.5 ZnO 0-2.5 B.sub.2O.sub.3 0-1.0 Al.sub.2O.sub.3
19-25 SiO.sub.2 55-69 TiO.sub.2 1-3 ZrO.sub.2 1-2.5 SnO.sub.2 0-0.4
.SIGMA.SnO.sub.2 + TiO.sub.2 <3 P.sub.2O.sub.5 0-3.0
Nd.sub.2O.sub.3 0.01-0.4 CoO 0-0.004
optionally with the additions of chemical refining agents such as
As.sub.2O.sub.3, Sb.sub.2O.sub.3, and CeO.sub.2 and refining
additives, such as sulfate compounds, chloride compounds, and
fluoride compounds in total contents of up to 2.0% by weight.
[0031] The oxides Li.sub.2O, Al.sub.2O.sub.3 and SiO.sub.2 are
components for the formation of high-quartz and/or keatite mixed
crystal phases that are necessary within the preferred limits
indicated in the claims. Li.sub.2O contents of over 4.5% by weight
are critical for the devitrification resistance in the production
of glass ceramic plates. The Al.sub.2O.sub.3 content is at least
19% by weight and is limited--to avoid high viscosities of the
glass and because of the undesirable devitrification of mullite
phases during shaping- to a maximum 25% by weight, preferably 24%
by weight. The SiO.sub.2 content is to be 55 to a maximum of 69% by
weight, preferably a maximum up to 68% by weight, since this
component greatly increases the viscosity of the glass. For melting
the glasses and with respect to the temperature stress during
shaping, higher contents of SiO.sub.2 are therefore
disadvantageous.
[0032] The addition of alkalis Na.sub.2O and K.sub.2O in amounts
of, in each case, up to 1.5% by weight, the alkaline-earths CaO up
to 1.5% by weight, SrO up to 1.5% by weight, BaO up to 2.5% by
weight and B.sub.2O.sub.3 up to 1% by weight improve the
meltability and the devitrification behavior during shaping. The
contents are limited, however, since these components essentially
remain in the residual glass phase of the glass ceramic and
increase the thermal expansion in an unreliable way. Thus, they
have a disadvantageous effect on the temperature resistance of the
glass ceramic plates. The sum of the alkalis Na.sub.2O+KO.sub.2 is
to be at least 0.2% by weight, preferably at least 0.3% by
weight.
[0033] As additional components, MgO, ZnO and P.sub.2O.sub.5 can be
incorporated in the crystal phase. Because of the problem of
forming undesirable crystal phases with higher thermal expansion,
such as, e.g., Zn spinel during glazing, the ZnO content is limited
to values of at most 2.5% by weight, preferably at most 2.0% by
weight. The MgO content is limited to at most 2.0, preferably 1.5%
by weight, since it otherwise unreliably increases the thermal
expansion of the glass ceramic. For low inherent colors, MgO
contents of less than 0.8% by weight and in particular less than
0.6% by weight are advantageous. A minimum MgO content of 0.1% by
weight is generally required, so that the thermal expansion of the
glass ceramic between 20.degree. C. and 700.degree. C. does not
drop to negative values below -0.3.times.10.sup.-6/K. The addition
of P.sub.2O.sub.5 can be up to 3% by weight and is preferably
limited to 1.5% by weight. The addition of P.sub.2O.sub.5 is
advantageous for the devitrification resistance; higher contents
have a disadvantageous effect on the acid resistance.
[0034] In the information, the Nd content is converted onto an
oxide base (Nd.sub.2O.sub.3), whereby the type of Nd additive in
the batch is not limited to the indicated oxide, but rather any Nd
compounds can be added.
[0035] The contents of the nucleating components TiO.sub.2,
ZrO.sub.2, and SnO.sub.2 are to be controlled within relatively
narrow limits. Certain minimum contents are necessary to produce
high density during the desired short glazing times of less than
2.5 hours, so that after the high-quartz mixed crystals are grown,
transparent glass ceramics can be produced without disruptive
turbidity.
[0036] For an effective nucleation, in any case a minimum content
of TiO.sub.2 of 1% by weight is necessary. The TiO.sub.2 content is
to be a maximum of 3% by weight, preferably at most 2.7% by weight,
since this component is involved in the formation of Fe/Ti and
Sn/Ti color complexes that disrupt the inherent color.
[0037] The content of SnO.sub.2 is not to exceed 0.4% by weight,
preferably 0.3% by weight, since otherwise it results in an
undesirable devitrification of an Sn-containing crystal phase
during shaping close to the processing temperature V.sub.A and
since the Sn/Ti color complexes contribute to the inherent
color.
[0038] The equivalent holds true for the content of ZrO.sub.2, in
which an upper limit of 2.5% by weight is to be maintained, so that
not only devitrification in the form of a ZrO.sub.2-containing
crystal phase (baddeleyite) results. An effort is to be made to
have the upper devitrification limit (OEG) be below the processing
temperature V.sub.A.
[0039] As chemical refining agents, the refining agents
As.sub.2O.sub.3 and/or Sb.sub.2O.sub.3, which are common for glass
ceramics from the Li.sub.2O--Al.sub.2O.sub.3--SiO.sub.2 system, can
be used. These refining agents are distinguished in that they exert
their refining action by releasing O.sub.2. The use of the
nucleating agent SnO2 is especially advantageous if the latter is
used in addition as a refining agent in connection with a
high-temperature refining of greater than 1700.degree. C., since
SnO.sub.2 cleaves the O.sub.2 that is required for refining at
these elevated temperatures. Additional refining agent additives,
such as, e.g., sulfate compounds, chloride compounds and fluoride
compounds, can be added to the glass melt. The total content of the
refining agent and refining additives is not to exceed 2% by
weight.
[0040] The water content of the starting glasses according to the
invention is usually between 0.015 and 0.06 mol/l, depending on the
selection of the raw materials of the batch and the process
conditions in the melt. This corresponds to .beta..sub.OH values of
0.16 to 0.64 mm.sup.-1.
[0041] According to a second further development of the invention,
the glass in an especially preferred embodiment contains the
following in % by weight based on oxide: TABLE-US-00002 Li.sub.2O
3.2-4.3 Na.sub.2O 0.2-1.0 K.sub.2O 0-0.8 .SIGMA.Na.sub.2O +
K.sub.2O 0.3-1.5 MgO 0.1-1.5 CaO 0-1.0 SrO 0-1.0 BaO 0-2.5 ZnO
0-2.0 Al.sub.2O.sub.3 19-24 SiO.sub.2 60-68 TiO.sub.2 1.0-2.7
ZrO.sub.2 1.2-2.2 SnO.sub.2 0-0.3 .SIGMA.SnO.sub.2 + TiO.sub.2
<2.7 P.sub.2O.sub.5 0-1.5 Nd.sub.2O.sub.3 200-3000 ppm CoO 0-30
ppm
optionally with the additions of chemical refining agents such as
As.sub.2O.sub.3, Sb.sub.2O.sub.3, and CeO.sub.2 and refining
additives such as sulfate compounds, chloride compounds, and
fluoride compounds in total amounts of up to 1.5% by weight.
[0042] In the case of low refining agent contents, it may be
necessary to combine the chemical refining with a high-temperature
refining above 1700.degree. C. if good bubble qualities with
numbers of bubbles <5 bubbles/kg of glass (relative to bubble
sizes >0.1 mm) are desired.
[0043] For the inherent color, it is especially advantageous if the
glass ceramic plate contains As.sub.2O.sub.3 as a refining agent,
optionally with additional refining additives such as sulfate,
chloride and fluoride compounds in total contents of up to 1% by
weight, and is plained without the refining agents Sb.sub.2O.sub.3
and SnO.sub.2.
[0044] By using 0.1-0.4% by weight of SnO.sub.2 as a refining agent
in combination with a high-temperature refining >1700.degree.
C., it is possible to obtain devitrification-stable starting
glasses (OEG <VA) with good bubble qualities.
[0045] The transparent coated glass ceramic plate according to the
invention with high-quartz mixed crystals as the prevailing crystal
phase is to have a thermal expansion coefficient of between room
temperature and 700.degree. C., which deviates from the zero
expansion by no more than 0.510.sup.-6/K. The deviation of less
than 0.310.sup.-6/K is to be preferred. With the low thermal
expansion coefficients, a high temperature difference resistance of
the glass ceramic plate is achieved.
[0046] To achieve especially good properties with respect to low
inherent color and high light transmission, it is advantageous if
the transparent glass ceramic plate according to the invention
contains less than 2.5% by weight of TiO2, less than 2000 ppm of
Nd.sub.2O.sub.3 and less than 20 ppm of CoO, and the
Fe.sub.2O.sub.3 content is less than 300 ppm, preferably less than
210 ppm. Thus, it is possible, with a 4 mm thickness, to achieve a
light transmission of greater than 80%, preferably greater than
85%, associated with low inherent color, i.e., a Yellowness Index
of less than 7% and a variegation of colors (chromaticity) in the
CIELAB system C* of less than 3.5.
[0047] To avoid disruptive light scattering (turbidity) of the
transparent glass ceramic plates in the production with short
glazing times, certain minimum contents of the nucleating agents
are necessary. The turbidity (English: haze) is to be less than 1%,
preferably less than 0.5% (measured for a 3.6 mm-thick plate with a
polished surface). According to ASTM D 1003, turbidity is the
proportion, in percent, of the transmitted light, which deviates
from the irradiated light beam on average by more than
2.5.degree..
[0048] Studies have shown that the nucleation action of SnO.sub.2
and TiO.sub.2 (in % by weight) is about the same. Therefore, these
two components can be considered together. The nucleation action of
the ZrO.sub.2 (in % by weight) is clearly greater than that of
TiO.sub.2 or SnO.sub.2. Therefore, the combinations of nucleating
agents ZrO.sub.2 and (TiO.sub.2+SnO.sub.2) can be produced with the
same nucleating action, and said combinations follow a
relationship. For the desired slight turbidity, there is
produced--in short glazing times of less than 2.5 hours, preferably
less than 100 minutes--for the minimum content of the nucleating
agents: ZrO.sub.2+0.87 (TiO.sub.2+SnO.sub.2).gtoreq.3.65
[0049] Additional limits are produced from the requirement for
lower inherent color: .SIGMA.SnO.sub.2+TiO.sub.2<2.7% by weight
and the requirement for devitrification resistance:
ZrO.sub.2<2.5% by weight SnO.sub.2<0.4% by weight.
[0050] On the other side, high nucleating agent contents result in
a deterioration of the devitrification behavior during shaping, as
was already explained. To ensure that the upper devitrification
temperature (OEG) is below the processing temperature VA, an upper
limit for the nucleating agent contents is produced, and said limit
follows the equation: ZrO.sub.2+0.87
(TiO.sub.2+SnO.sub.2).ltoreq.4.3
[0051] Similar to known glass ceramics, the glass ceramic plates
according to the invention can be converted into a glass ceramic
that contains keatite mixed crystals by an additional temperature
treatment at temperatures of between about 900 and 1200.degree. C.
Glass ceramics of this type have a higher temperature resistance,
but at the expense of an increase in the thermal expansion
coefficient, which is between room temperature and 700.degree. C.
on the order of magnitude of about 110.sup.-6/K. Because of the
crystal growth that accompanies the conversion, they have a
translucent to opaque-white appearance. The turbidity is generally
>50% in haze values.
[0052] The transparent coated glass ceramic plates according to the
invention are suitable especially as cooking surfaces for use in a
stove top. The opaque, colored temperature-stable coatings are
preferably on the side of the glass ceramic plate that is not used
and thus make it possible to provide color designs and to avoid the
disruptive view of the technical elements below the transparent
glass ceramic plate. In this case, the cooking zones of the glass
ceramic plate can be electrically radiant-heated, inductively
heated or gas-heated. In particular, in the case of electric
halogen heating elements, it is necessary--by the coating--also to
avoid the shielding action caused by the radiating heating
elements. In radiant heating, moreover, it is desirable that the
bottom coating be infrared-transparent to ensure short boiling
times. The most varied types and embodiments of bottom coatings are
possible according to the prior art. Thus, e.g., the bottom coating
can be designed differently in the hot areas and in the colder
areas of the glass ceramic plate.
[0053] The top of the glass ceramic plate, which also represents
the side that is used during use as a cooking surface, can be
decorated with decorative paints in the usual way. The decorative
embodiments can be designed to be expansive or compact and have
various degrees of surface coatings. The top decoration can also be
designed such that together with the colored bottom coating, it
produces certain impressions or designs.
[0054] For introducing color displays or screen displays, it is
advantageous if the transparent glass ceramic plate contains a
bottom coating with partial recesses. Indicators, displays, etc.,
can be attached under these recesses, which can be detected by the
recess through the glass ceramic plate. Because of the low inherent
colors according to the invention, the display indicators and
screens have high color fidelity. The light gray shade of the glass
ceramic plate according to the invention is very advantageously
produced in the displays compared to the brownish-yellow inherent
color without Nd.sub.2O.sub.3 content. When used as a cooking
surface, the glass ceramic plate according to the invention is
especially suitable for color LED or LCD displays, and future color
displays, screens and even televisions. In addition to the low
inherent color, the high light transmission is also advantageous
here. In this way, new functions, such as, e.g., showing cooking
recipes or interactive functions (Internet, integration with other
household appliances) or touch-screen control electronics can be
integrated advantageously under the transparent, color-free glass
ceramic plate.
[0055] The above-mentioned advantages are also used in a
corresponding way in other applications, e.g., as fireplace door
windows, fire protection glazings, oven door windows or in lamp
covers.
[0056] This invention becomes clearer with the aid of the following
examples.
[0057] The glasses of Table 1 were melted and plained with use of
raw materials that are common in the glass industry at temperatures
of about 1620.degree. C. The batch was melted in crucibles that
consist of sintered silica glass and then poured into the Pt/Rh
crucibles with inside crucibles made of silica glass and
homogenized at temperatures of about 1550.degree. C. for 30 minutes
while being stirred. After standing at 1640.degree. C. for 2 hours,
castings of about 140.times.100.times.30 mm in size were poured and
depressurized in an annealing furnace at about 660.degree. C. and
cooled to room temperature. Test patterns for the measurement of
the properties in the vitreous state and the plates for the glazing
were prepared from the castings. In Table 1, the Fe.sub.2O.sub.3
contents produced by raw material contaminants are also cited in
the compositions. The water content of the glasses is 0.03-0.05
mol/l, corresponding to .beta..sub.OH values of 0.32 to 0.53
mm.sup.-1.
[0058] Table 1 shows the compositions of the starting glasses Nos.
1 to 8 according to the invention and the starting glasses 9 to 10
according to the prior art for comparison. The starting glass 10
corresponds to a composition without Nd additive that is optimized
relative to inherent color. This optimization is at the expense of
a higher processing temperature V.sub.A and strong negative thermal
expansion .alpha.20/700 of the glass ceramic. Variegation of colors
and Yellowness Index are comparatively higher values.
[0059] In Table 1, the properties in the vitreous state, such as,
e.g., transformation temperature Tg, processing temperature
V.sub.A, upper devitrification limit OEG, thermal expansion between
room temperature and 300.degree. C., as well as the density are
also cited. Based on the composition, in particular the nucleating
agent content is the upper devitrification limit below the
processing temperature V.sub.A.
[0060] The glazing of the starting glasses was carried out with the
following temperature/time programs:
[0061] Glazing Program 1, (Total Time 147 Minutes):
[0062] In 50 minutes from room temperature to 790.degree. C.
[0063] 30 minutes of holding time at 790.degree. C.
[0064] In 30 minutes from 790 to 900.degree. C.
[0065] 7 minutes of holding time at 900.degree. C.
[0066] In 30 minutes from 900 to 750.degree. C.
[0067] Quick cooling to room temperature
[0068] Glazing Program 2, (Total Time 96 Minutes):
[0069] In 38 minutes from room temperature to 790.degree. C.
[0070] 14 minutes of holding time at 790.degree. C.
[0071] In 24 minutes from 790 to 900.degree. C.
[0072] 10 minutes of holding time at 910.degree. C.
[0073] In 10 minutes from 910 to 800.degree. C.
[0074] Quick cooling to room temperature
[0075] Glazing Program 3, (Production of Keatite Mixed Crystal
Glass Ceramic):
[0076] In 33 minutes from room temperature to 790.degree. C.
[0077] 30 minutes of holding time at 790.degree. C.
[0078] In 32 minutes from 790.degree. C. to a maximum temperature
[0079] T.sub.max
[0080] 7 minutes of holding time at T.sub.max
[0081] Quick cooling to room temperature
[0082] Tables 2 and 3 show the properties of the transparent glass
ceramics with high-quartz mixed crystals as the prevailing crystal
phase, which were produced with the glazing program 1 (Table 2) or
2 (Table 3). Examples 9 and 10 as well as 19 and 20 are comparison
ceramics outside of the invention. The transmission measurements
were made on polished plates with a thickness of 4 mm and with
standard illuminant C, 2.degree.. In addition to the color
coordinates L*, a*, and b* in the CIELAB system, the color
coordinates x and y in the CIE system are also cited. The glass
ceramics according to the invention confirm the advantageous action
of the Nd feedstock and optionally in addition Co for reducing the
disruptive inherent color (Yellowness Index, variegation of colors
C*). High values of the light transmission (brightness) Y are also
achieved.
[0083] The turbidity was measured with standard illuminant C on 3.6
mm-thick plates that are polished on both sides and with a
commercial haze-guard plus measuring device of the BYK-Gardner
Company and characterized by the haze value.
[0084] Transparent glass ceramic plates that are 4 mm thick with
polished surfaces were provided with a coating that consists of a
high-temperature-stable silver-metallic-colored luster paint
according to the prior art (DE 10014373 C2). The coating was baked
on in an additional temperature treatment at 800.degree. C. First,
the color of the coating was directly measured with a measuring
device of the Datacolor Company, designation Mercury 2000, in
remission (incident light) with standard illuminant C, 2.degree..
In the CIELAB system, the values are L*=78.5, a*=1.7, and b*=9.6,
and the variegation of colors is C*=9.7. The measurements were now
performed with this device, such that the color of the coating
through the transparent glass ceramic plate was determined. The
light irradiates the transparent glass ceramic plate, is partially
absorbed and reflected on the colored bottom coating before it then
passes again through the glass ceramic plate and reaches the
observer. The disruptive influence of the inherent color of the
transparent glass ceramic plate is produced during the measurement
by altering the L*, a*, and b* values compared to the values
measured directly on the coating. The measurements (Tables 2 and 3)
confirm the advantageous action of the color-free, transparent
glass ceramic plates according to the invention.
[0085] For the glazing program 1, in addition property values of
the glass ceramics, such as infrared transmission at 1600 nm,
thermal expansion between 20 and 700.degree. C., density and the
phase content of the main crystal phase that is measured with x-ray
diffraction, that consist of high-quartz mixed crystals, as well as
the mean crystallite size, are also indicated.
[0086] For the glazing programs with total times of 147 minutes and
96 minutes, low degrees of turbidity (haze values) are achieved by
the selection of the nucleating agents.
[0087] In addition, some examples were converted with the glazing
program 3 into translucent glass ceramics with keatite mixed
crystals as a prevailing crystal phase and properties were
determined (Table 4). The maximum temperatures T.sub.max during
production are indicated in the table. Light transmission Y and the
IR transmission at 1600 nm were measured on 3.6 mm-thick plates.
The color values L*, a* and b* were determined in remission
(incident light) on 3.6 mm-thick polished plates with the measuring
device Mercury 2000, standard illuminant C, 2.degree.. The haze
values of the examples (polished plates, 3.6 mm thickness) are more
than 90%.
[0088] FIG. 1 shows the transmission spectra of the glass ceramic
of Example 8 according to the invention and the comparison glass
ceramic of Example 9. The comparison example shows the disruptive
coloring associated with a high Yellowness Index and chromaticity.
The glass ceramic according to the invention shows the
characteristic absorption bands of the Nd ion, which are extremely
well suited also for labeling the glass ceramic plates according to
the invention. Moreover, they also simplify the recycling of the
glass ceramic by optical cullet separation processes based on the
absorption bands and the infrared fluorescence of the Nd ion.
[0089] FIG. 2 shows the color coordinates of the glass ceramics
according to the invention, Examples 11 to 18, and the comparison
glass ceramics, Examples 19 and 20, in the CIELAB system.
TABLE-US-00003 TABLE 1 Compositions and Properties of Starting
Glasses According to the Invention and Comparison Glasses 9 and 10
Compositions in % by Weight Based Glass No. on Oxide 1 2 3 4 5 6 7
8 9 10 Al2O3 21.3 21.3 21.8 21.65 20.0 19.95 20.1 20.0 19.9 22.0
BaO -- -- 1.98 1.95 0.80 0.84 0.82 1.21 0.9 1.4 K2O 0.13 0.11 -- --
0.20 0.20 0.20 -- 0.22 0.27 Li2O 3.75 3.70 3.69 3.64 3.54 3.75 3.65
3.63 3.6 4.15 MgO 0.85 1.05 0.58 0.59 1.15 1.06 1.10 0.77 1.2 --
Na2O 0.35 0.36 0.52 0.50 0.15 0.16 0.15 0.45 0.20 0.40 P2O5 -- --
-- -- -- -- -- -- -- 1.33 SiO2 67.55 67.35 65.3 65.2 68.1 67.35
67.4 67.22 67.2 65.5 ZnO 1.57 2.0 1.70 1.57 1.48 1.60 1.54 1.57
1.55 -- SnO2 -- 0.11 -- -- -- -- -- -- -- -- TiO2 2.23 2.19 2.29
2.38 2.26 2.35 2.35 2.33 2.59 2.13 ZrO2 1.76 1.80 1.76 1.98 1.76
1.80 1.76 1.77 1.75 2.26 As2O3 0.40 -- 0.28 0.43 0.40 0.86 0.85
0.86 0.86 0.44 Sb2O3 -- -- -- -- -- -- -- -- -- 0.10 Nd2O3 0.09
0.02 0.08 0.09 0.14 0.06 0.06 0.17 -- -- Fe2O3 ppm 200 100 180 200
200 140 150 160 290 220 CoO ppm -- -- -- -- -- -- -- 5 -- -- NiO
ppm -- -- -- -- -- -- 23 -- -- -- Tg .degree. C. 681 685 6.76 687
692 669 682 672 673 710 V.sub.A .degree. C. 1320 1320 1306 -- 1335
1315 -- 1325 1304 1340 OEG .degree. C. 1240 1270 1250 -- 1255 1280
-- 1265 1265 1315 .alpha..sub.20/300 10.sup.-6/K 3.87 3.88 4.08
4.05 3.79 3.90 3.90 3.91 3.87 4.24 Density g/cm.sup.3 2.436 2.446
2.472 2.479 2.444 2.451 2.450 2.447 2.454 2.431
[0090] TABLE-US-00004 TABLE 2 Properties of Glass Ceramics
According to the Invention and Comparison Glass Ceramics of
Examples 9 and 10 (Glazing Program 1) Example No. 1 2 3 4 5 6 7 8 9
10 Glass No. 1 2 3 4 5 6 7 8 9 10 Transmission 4 mm Standard
Thickness % Illuminant C, 2.degree. Light 87.0 87.3 87.7 86.3 85.6
87.2 85.6 83.8 84.8 89.4 Transmission Y Yellowness 3.3 5.4 3.5 4.0
2.8 5.8 6.3 2.1 15.0 5.9 Index X 0.3126 0.3148 0.3128 0.3133 0.3121
0.3150 0.3156 0.3117 0.3239 0.3151 Y 0.3197 0.3215 0.3199 0.3206
0.3195 0.3222 0.3223 0.3183 0.3319 0.3224 L* 94.6 94.8 94.9 94.3
94.0 94.7 94.1 93.3 93.6 95.6 a* -0.5 -0.3 -0.4 -0.6 -0.6 -0.5 -0.3
-0.2 -0.7 -0.5 b* 1.8 2.8 1.9 2.2 1.6 3.1 3.2 1.1 8.1 3.2 C* 1.8
2.8 1.9 2.2 1.7 3.1 3.2 1.1 8.1 3.2 IR Transmission 4 mm 87.7 89.5
89.1 87.9 87.7 69.0 87.9 88.3 85.7 86.7 1600 nm Thickness % Color
of Bottom 4 mm Coating Measured Thickness % through Glass Ceramic
(Remission) L* 76.71 76.65 75.88 76.29 75.68 76.59 75.85 74.63
74.90 77.48 a* 1.21 1.84 1.49 1.26 1.19 1.32 1.99 1.71 1.68 1.23 b*
10.49 11.98 11.40 11.06 10.25 12.42 12.29 9.50 18.69 12.83 c* 10.56
12.12 11.49 11.13 10.32 12.49 12.45 9.66 18.76 12.89
.alpha..sub.20/700 10.sup.-6/K -0.26 -0.05 -0.10 +0.03 +0.11 -0.07
+0.10 -0.05 +0.14 -0.46 Density g/cm.sup.3 2.519 2.526 2.545 2.550
2.534 2.543 2.538 2.544 2.546 2.509 X-Ray Diffraction: High-Quartz
% 73 72 71 68 71 76 72 71 75 75 Phase Content Crystallite nm 33 32
40 37 28 40 30 33 41 38 Size Turbidity 3.6 mm 0.28 0.28 0.50 0.42
0.27 0.23 0.25 0.32 0.20 0.27 Haze Thickness %
[0091] TABLE-US-00005 TABLE 3 Properties of Glass Ceramics
According to the Invention and Comparison Glass Ceramics of
Examples 19 and 20 (Glazing Program 2) Example No. 11 12 13 14 15
16 17 18 19 20 Glass No. 1 2 3 4 5 6 7 8 9 10 Transmission 4 mm
Standard Thickness % Illuminant C, 2.degree. Light 86.5 86.6 86.8
86.1 85.6 87.6 85.1 84.0 85.4 89.4 Transmission Y Yellowness 4.1
5.8 4.9 3.9 2.8 5.4 6.1 1.6 13.8 6.2 Index X 0.3133 0.3152 0.3141
0.3131 0.3121 0.3146 0.3154 0.3112 0.3228 0.3153 Y 0.3207 0.3220
0.3214 0.3204 0.3195 0.3220 0.3222 0.3178 0.3307 0.3227 L* 94.4
94.5 94.5 94.2 94.0 94.8 93.9 93.4 93.9 95.6 a* -0.6 -0.3 -0.6 -0.6
-0.6 -0.6 -0.3 -0.2 -0.7 -0.6 b* 2.2 3.0 2.6 2.1 1.6 2.9 3.1 0.8
7.5 3.4 C* 2.3 3.0 2.7 2.2 1.7 3.0 3.1 0.8 7.5 3.4 Color of Bottom
4 mm Coating Measured Thickness % through Glass Ceramic (Remission)
L* 76.37 76.58 75.93 76.63 75.94 76.08 75.53 74.98 74.92 77.61 a*
1.33 1.73 1.35 1.12 1.13 1.30 1.89 1.73 1.80 1.24 b* 11.34 12.34
11.75 10.85 10.14 12.31 12.37 9.07 18.67 12.99 c* 11.40 12.46 11.83
10.91 10.20 12.37 12.51 9.24 18.76 13.05 Turbidity 3.6 mm 0.31 0.34
0.65 0.52 0.27 0.28 0.39 0.29 0.27 0.41 Haze Thickness %
[0092] TABLE-US-00006 TABLE 4 Properties After Conversion into
Keatite Glass Ceramic, (Glazing Program 3) Example No. 21 22 23 24
25 Glass No. 2 4 6 8 9 Maximum .degree. C. 1120 1100 1090 1090 1080
Temperature T.sub.max Transmission 3.6 mm Standard Illuminant C,
2.degree. Thickness Light Transmission Y % 9.0 6.4 4.5 5.0 3.9 IR
Transmission 1600 nm % 79.9 68.3 49.8 58.6 56.1 Color (Remission)
3.6 mm L* Thickness 84.51 87.79 90.91 87.22 87.32 a* % -3.29 -2.73
-1.71 -1.52 -1.02 b* -6.23 -6.30 -2.98 -7.56 -2.36 c* 7.04 6.87
3.44 7.71 2.57 .alpha..sub.20/700 10.sup.-6/K +0.91 +1.26 +1.00
+1.02 +1.05 Density g/cm.sup.3 2.515 2.544 2.513 2.522 2.516 X-Ray
Diffraction: Keatite Phase Content % 88 83 86 85 89 Keatite
Crystallite Size nm n.d. >120 99 >120 --
[0093] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0094] In the foregoing and in the examples, all temperatures are
set forth uncorrected in degrees Celsius and, all parts and
percentages are by weight, unless otherwise indicated.
[0095] The entire disclosures of all applications, patents and
publications, cited herein and of corresponding European
application No. EP 06 005 598.5, filed Mar. 20, 2007, is
incorporated by reference herein.
[0096] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples. From the foregoing description, one skilled in
the art can easily ascertain the essential characteristics of this
invention and, without departing from the spirit and scope thereof,
can make various changes and modifications of the invention to
adapt it to various usages and conditions.
* * * * *