Stock material or miscellaneous articles – Hollow or container type article – Glass – ceramic – or sintered – fused – fired – or calcined metal...
Reexamination Certificate
1999-01-19
2001-03-13
Speer, Timothy M. (Department: 1775)
Stock material or miscellaneous articles
Hollow or container type article
Glass, ceramic, or sintered, fused, fired, or calcined metal...
C428S034500, C428S034600, C138S145000, C138S146000
Reexamination Certificate
active
06200658
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making a hollow, interiorly coated glass body from a glass tube made of a low melting glass material and acting as semifinished product or intermediate product.
The invention also relates to a glass tube made from low melting glass material and acting as a semifinished product for forming a hollow glass body with an interior coating having a high chemical resistance or inertness.
2. Prior Art
Low melting glass materials, such as borosilicate glasses or calcium, sodium glasses, corrode in a known manner on contact with water or other liquids. Particularly water withdraws sodium ions from glass.
Thus it is necessary for numerous applications to increase the chemical resistance of the glass bodies, which are formed from this type of low melting glass, especially hollow glass bodies formed from glass tubes.
Hollow glass bodies, which require an increased chemical resistance for the interior surface, are, for example, those used
for chemical plant structures,
for flow meters for chemically reactive media,
for analytical purposes (e.g. burette tubes, titration cylinders, etc.),
for reagent glasses for special purposes,
for sheathing of measuring electrodes in reactive media,
for illumination purposes, e.g. halogen lamps,
for discharge lamps,
for components used for biotechnology reactors, and
as containers for medicinal purposes (e.g. ampoules, bottles, injector devices, cylindrical ampoules, etc.).
The latter mentioned applications are of special significance.
It is indeed known to make glass tubes from silica glass (quartz glass, SiO
2
glass) as a semifinished product for forming hollow glass bodies, which have a very high chemical resistance. Those glass tubes are however very expensive because of the high melting point of the SiO
2
glass. Furthermore they can only be made with limited optical quality and are less suitable for mass production. These tubes may be formed with only very special apparatus since, on the one hand, their forming temperatures are very high and, on the other hand, the temperature interval in which their formation is possible is very small.
Semifinished glass tubes made from silica glass thus may not be of sufficient quality and are uneconomical for mass applications.
Predominantly low melting glasses, e.g. borosilicate glasses or calcium-sodium glasses, are used for large-scale glass products. These may advantageously be formed as tubes economically.
For example these glasses include the following: Duran®-borosilicate glass (Schott Glas), Fiolax®klar(Schott glass, Fiolax®braun(Schott Glas) and Kimble N 51 A (Fa. Kimble).
The compositions of these glasses made in the form of glass tubing are tabulated in the following Table I.
TABLE I
GLASS COMPOSITIONS IN % by WEIGHT*
GLASS
SiO
2
B
2
O
3
Al
2
O
3
Na
2
O
K
2
O
MgO
CaO
BaO
1
69
1.0
4
12.5
3.5
2.5
5
2
2
69
1.0
4
12.5
3.5
2.5
5
2
3
69
1.0
4
12.5
3.5
2.5
5
2
4
70
1.0
4
12.5
3.5
2.5
5
2
5
69
1.0
4
12.5
3.5
2.5
5
2
6
69
1.0
4
12.5
3.5
2.5
5
2
7
75
11
5
7
1.5
0.5
8
75
11
5
7
1.5
0.5
9
80
13
2.5
3.5
0.5
10
70.8
8
5.5
7
1.5
1
2
11
70.8
8
5.5
7
1.5
0.5
2
12
72.8
11
7
7
1
1
13
73.3
10
6
6
3
0.5
14
74.3
10
6
8
1
*balance to 100% consists of other elements (for No. 10 and No. 11 Fe
2
O
3
and TiO
2
which together are 3.5%)
It is known to increase the chemical resistance of these glass tubes made from low melting glass by a method in which the glass surface is chemically leached out. A sutable reactive gas (SO
2
, (NH
4
)
2
SO
4
or HCl) is conducted through the still warm glass tube, which leads to a surface reaction and a reduction in the alkali content at the surface.
This type of dealkalizing process is, e.g., described in H. A. Schaeffer, et al, Glastechn. Ber. 54, Nr. 8. pp. 247 to 256. The disadvantage of this process is that predominantly toxic gasses are used, whereby the glass surface can contain traces of these reactive reaction gases after this chemical treatment and the glass surface structure is damaged which leads to an increased surface area and to an increase in reactive sites on the surface. Furthermore the use of these reactive gases is undesirable from an environmental standpoint and due to worker safety consideration. With many of the suggested gases corrosive by-products arise, which react strongly with metal apparatus parts. Furthermore particles can be released from the porous damaged surfaces during shaping or forming of this type of leached out glass tube. Also a washing process for removal of reaction products is necessary prior to use of the leached out glass tube. This washing process necessitates a drying and disposal of reaction products, i.e. the costs increase for making the semifinished glass tubes.
An additional process for dealkalizing low melting glass by fluorination by means of fluoro-acids, which has the same main disadvantages as the above-described process, is described in U.S. Pat. No. 3,314,772.
In order to avoid the disadvantages of dealkalizing process it is also known to provide a tubular glass container from low melting glass material, which operates as a packaging device for pharmaceutical materials, having a silicon dioxide (SiO
2
) layer on its interior surface, which has the same inertness as a quartz glass surface (M. Walther, “Packaging of sensitive perenteral drugs in glass containers with a quartz-like surface”, in Pharmaceutical Technology Europe, May, 1996, Vol. 8, Nr. 5, pp. 22 to 27.
The coating of the interior surface of the formed glass body occurs by chemical deposition of an oxide coating from the gas phase, especially by means of a vacuum-assisted plasma CVD process (PECVD=plasma enchanced chemical vapor deposition), in particular by means of a pulsed plasma process (PICVD=plasma impulse chemical vapor deposition).
This PECVD or PICVD method for coating of an interior of a hollow body, especially made from plastic, is known from German Patent Documents DE 196 29 877 and DE-Z “Multilayer Barrier Coating System produced by Plasma-impulse Chemical Vapor Deposition(PRCVD)” by M. Walther, M. Hemming, M. Spallek, in “Surface and Coatings Technology” 80, pp. 200 to 205 (1966).
In the known case (DE 296 09 958 U1) the finished containers, i.e. the glass bodies themselves, are interiorly coated. Because of that each glass container, must be subjected to an expensive coating process, adapted to its form.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple and economical method of making a hollow glass body made from a low melting glass material.
It is another object of the present invention to provide a semifinished glass tube for making the hollow, interiorly coated glass body of the invention.
These objects and others which will be made more apparent hereinafter are attain in a process of the above-described type for making a hollow, interiorly coated glass body from a glass tube made of low melting glass material and acting as a semifinished product or intermediate.
According to the invention this process includes the steps of:
coating the interior surface of the semifinished glass tube with an oxide material to form an interior coating having a coating thickness which is adapted to the subsequent shaping or working conditions required for making the glass body and the chemical resistance requirements of the glass body, and
making the glass body from the interiorly coated semifinished glass tube.
The glass tube according to the invention acting as the semifinished product or intermediate for making the glass body has an interior surface provided with a coating of oxide material whose coating thickness adapted to the subsequent shaping or working conditions required for making the glass body and the chemical resistance requirements of the glass body.
Glass tubes are prepared with the methods of the invention whose chemical resistance is largely maintained after a working or shaping process. These working or shaping processes can include constrictions, melting and shaping at the ends of
Danielzik Burkhardt
Heming Martin
Segner Johannes
Spallek Michael
Walther Marten
Schott Glas
Speer Timothy M.
Striker Michael J.
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