The present invention relates to a method for the production of packaging made from glass for pharmaceutical products and medical products where a tube consisting of a base glass, such as borosilicate glass, is converted to a glass product by hot-forming.
Glass tubes have been known for many years as pharmaceutical packaging and packaging for medical products, such as syringes, ampoules, etc. For this purpose, thin glass tubes are initially drawn from the melt and are then, in an additional process, converted to the final product by hot-forming. Large-scale production technologies normally use borosilicate glasses, as these offer a relatively high chemical resistance. However, it has been found that the surface quality is not always sufficient to meet all demands.
While tubes made from quartz glass are not connected with that disadvantage and offer high chemical resistance, quartz glass can be produced and processed only with high input so that it does not lend itself for economical mass production.
In order to avoid the disadvantages connected with quartz glass one has tried to coat the inner surfaces of glass containers, formed as tubes from low-melting glass, with a silicon oxide layer or another oxide layer with the aim to obtain highly resistant inner surfaces (compare DE 198 01 861 A1).
The inner surface of the semi-finished glass tube is coated for this purpose with a layer of oxidic materials (SiO2, Al2O3, TiO2 or mixtures thereof) of a thickness adapted to the subsequent process conditions prevailing in the conversion of the formed glass body and the demands placed on the chemical resistance. Thereafter, the formed glass body is produced by converting the semi-finished glass tube with the coating on its inside. The coating on the inner surface may be produced from the liquid phase according to the sol-gel method or by separation from a solution supersaturated with an acidic coating material. Preferably, however, coating of the inner surface is effected by chemical separation of the oxidic coating material from its gas phase (CVD method).
While separation from the gas phase is a very complex and expensive process, coating of the inner surfaces by the sol-gel method not always resulted in satisfactory solutions offering satisfactory chemical resistance.
Further, it has been known in the art (DE 1 421 844) to apply a vaporization process using acid gasses (sulfur oxide or haloid acid gas) at raised temperatures in order to achieve alkali leaching of the surface of soda-aluminum-oxide silicate glasses and, thus, to improve the resistance and/or mechanical strength of the glass products.
In view of this, it is a first object of the invention to disclose a method for the production of packaging made from glass for pharmaceutical products and medical products.
It is a second object of the invention to disclose a method for the production of packaging made from glass which is suited for large-series production.
It is a third object of the invention to disclose a method for the production of packaging made from glass which makes the production of such packaging as simple and cost-effective as possible.
It is a forth object of the invention to disclose a method for the production of packaging made from glass which provides for a high surface quality.
These and other objects of the invention are achieved by a method for the production of glass packaging for pharmaceutical products and medical products comprising the steps of:
(a) Providing a tube made from a base glass and provided with a temporary interface layer on its inner surface;
(b) hot-forming the tube at a temperature above the glass transformation temperature Tg; and
(c) cooling down the tube to room temperature.
The object of the invention is thus perfectly achieved.
It has been found, especially with borosilicate glasses, that borates vaporize during hot-forming of the tube and attack the inner surface of the tube, which leads to deterioration of the surface quality and increases the susceptibility to leaching.
By producing a temporary protective layer on the inner surface of glass tubes prior to the hot-forming process, that damaging attack by the materials vaporizing during the hot-forming process can be prevented. Another advantage of the temporary interface layer is seen in the fact that it avoids, or at least reduces, the adhering tendency of loose particles that may be encountered, for example, during isolation of the tubes.
Consequently, on the one hand borate-induced surface deficiencies such as corrosion cavities and superficial vitrification are reduced or even prevented, and on the other hand no detrimental modification of the zone near the surface (“altered layer”) is encountered.
As a result, one in particular achieves an improved morphological surface quality. And the alkali leaching values are improved as well.
According to a further embodiment of the invention the temporary protective layer may be removed later by a washing step, for example.
According to a further embodiment of the invention the temporary interface layer is generated in-situ by applying an acid gas or by applying a gas burner, such as a propane gas burner while producing the tube by means of drawing.
This leads to the advantage that the generation of the temporary protective layer can be combined with the tube generating process, so that almost no slow-down is expected during manufacturing.
Alternatively, the temporary interface layer can be generated after the tube generating process, preferably on tubes that have been isolated already.
Thereby the tube generation and the generation of the temporary interface layer can be decoupled from each other.
The temporary interface layer may later be removed, e.g. by washing off.
Since the removable temporary can be removed without any problem as part of the washing step anyway required for the packaging before the units are filled with pharmaceutical products and medical products, a very simple and low-cost production process is guaranteed, practically without any additional costs. This means that the invention simultaneously improves the quality of the inner glass surface and the resistance to leaching.
Preferably, the base glass is a borosilicate glass, and hot-forming preferably is carried out at a temperature of 1000° C. to 1300° C., preferably at 1100° C. to 1300° C.
As far as the temporary interface layer is produced by injecting a salt solution, herein the salts may be sprayed into the respective tube part before hot-forming.
The manner in which the temporary interface layer is produced is not of fundamental importance. The temporary interface layer, serving as a protective layer during the hot-forming process, blocks the attacks by boron-oxygen-containing particles on the glass surface. This guarantees in any case a reduction of the detrimental effect of evaporated glass components during the hot-forming process.
As the temporary interface layer as such is of a temporary nature only and can be removed for example by washing, it acts to protect the remaining surface layer of the product being produced.
According to a preferred embodiment of the invention, the temporary interface layer is removed by a washing step after hot-forming of the tube.
That washing step may be carried out with de-ionized water at a temperature above room temperature, preferably in the range of 50° C. to 70° C.
That feature provides the advantage that no additional washing step is required for removing the temporary interface layer since that washing step can be combined with the washing step anyway required before the products can be used as pharmaceutical packaging.
The method according to the invention preferably is used for the production of all products that are made from glass tubes, in particular for the production of vials, syringes, carpoules and ampoules or for the production of glass tubes per se.
It was found that a short time span is sufficient for generating the temporary interface layer, such as 600 seconds, preferably 60 seconds, or 30 seconds, or even 10 seconds at the most.
Surprisingly it was found that a protective effect is reached already with a temporary interface layer that doesn't exist as a complete layer, but exists only partially.
It is understood that the features of the invention mentioned above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation, without leaving the scope of the invention.
Further features and advantages of the invention will become apparent from the description that follows of certain preferred embodiments, with reference to the drawing. In the drawings:
For comparison,
According to
In contrast, a glass tube 10b according to the invention, illustrated in
The inner surface of glass tubes made from borosilicate glass (type Fiolax®, produced and marketed by Schott AG, Mainz) was subjected to a gassing operation using a gas mixture composed of 50% SO2 and 50% air, where the mixture had a water content of 40 g/m3. The SO2 gas treatment was carried out for 600 seconds. The tube sections so treated were formed into vials of a desired dimension at a temperature of approximately 1200° C., using a forming machine. The inner surfaces, with and without SO2 gas treatment, were examined by scanning electron microscopy (SEM). Following the forming process the glass tubes were rinsed for 10 minutes at 60° C. using de-ionized water. Finally, sodium leaching of the conventional glass tubes, and the glass tubes according to the invention was tested by autoclaving (60 minutes at 121° C. with de-ionized water).
The “gas treated” tube surfaces show (before the forming operation) a dense coat of crystals, as can be seen in the SEM plot of
Surface defects of the kind typically produced in conventional glass tubes (compare
The leaching effect on glass tubes that had been provided with a temporary interface layer by SO2 gassing was lower by approximately 22% in average than the leaching effect on conventional glass tubes (compare sodium leaching according to
All glass tubes were formed on the same machine and in the same format.
The inner surface of glass tubes made from borosilicate glass (Type Fiolax®, produced and marketed by Applicant) was treated using a propane gas flame, either (a) stationarily for a defined time or (b) continuously at a constant speed. Thereafter, corresponding glass tubes were produced from the tube sections so conditioned using a hot-forming machine.
The sodium leaching value is lower by approximately 20% in average for the glass tubes produced according to the invention.
Number | Date | Country | Kind |
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10 2008 051 614.7 | Oct 2008 | DE | national |