LU83731A1 - PROCESS FOR DESALCALIZING THE INTERNAL SURFACE OF HOLLOW GLASS OBJECTS - Google Patents

Description

The present invention relates to a process for desalkalinizing the internal surface of hollow glass objects, for example of the soda-lime or borosilicate type, such as tubes, bottles, flasks and containers in general.

It is known that the commercial glasses commonly used for the manufacture of hollow glass objects, in particular bottles and flasks, undergo, in contact with water and other liquids, a corrosion which is manifested by a soda extraction which can contaminate the contents of these containers.

It is also known that glass containers or flasks intended to contain, for example, pharmaceutical products must have an internal surface having a hydrolytic resistance less than a limit value fixed by a standard, such as the standard of the European Pharmacopoeia (edition 1974, vol. 2, pages 87 to 93). The hydrolytic resistance of the internal surface of glass vials is measured, according to this standard of the European Pharmacopoeia, by titrating, using 0.01 N hydrochloric acid, a determined volume of distilled water subjected to a treatment. thermal determined in an autoclave in said stoppered bottle.

The limit values according to the standard of the European Pharmacopoeia measured in ml of 0.01 · N HCl per 100 ml of water, for various vials are as follows: - vials with a capacity of 50 to 100 ml: 0.5 ml - bottles with a capacity of 20 to 50 ml î 0.6 ml - bottles with a capacity of .10 to 20 ml: 0.8 ml - bottles with a capacity of 5 to 10 ml i 1 ml

To be acceptable, the bottles must therefore have, according to their capacity, a hydrolytic resistance lower than the maximum values indicated above, expressed in ml of 0.01 N HCl per 100 ml of extraction water.

A process is known for de-alkalinization of the internal surface of glass bottles or flasks, consisting essentially of injecting therein, when they are still at a high temperature after leaving the forming machine, sulfuric anhydride ( SO ^) obtained by oxidation! sulfur dioxide (SOg) catalytic using oxygen.

This known method has various drawbacks. Thus, the dealkalization reaction using sulfuric anhydride requires, in practice, the simultaneous treatment using dry water vapor playing the role of activator of this reaction. In addition, the modes known treatment of glass vials using sulfuric anhydride do not allow to obtain vials whose inner surface has a hydrolytic resistance. lower than the maximum value set by the standard of the European Pharmacopoeia, in particular for vials with a capacity of less than approximately 100 ml, in particular 5 to 50 ml soda-lime-type glass vials intended, inter alia, to contain pharmaceutical products.

Also known, in particular from Belgian patent n ° 697-122, a process for increasing the surface durability of soda-lime glasses, consisting in exposing such a surface to the action of fluorine to a sufficient degree to produce a significant exchange fluorine ions with oxygen and / or hydroxyl ions on the surface of the glass, but not sufficient to produce a perceptible chemical attack on this surface. In this known process, exposure to fluorine takes place at a temperature higher than the deformation temperature of the glass.

Among the fluorinated compounds used in this known process, there may be mentioned, by way of examples, the polyhalogenated derivatives of methane and of ethane containing fluorine, such as difluoro-dichloromethane (C Clg F £) or Freon 12, trifluoromethane (CHF ^) or Freon 23, trifluoromonochloromethane (C Cl F ^) or Freon 13 and 1-difluorochloro-2-dichloroethane (C Clg - C Cl F ^) or Freon 114.

This known method of treating glass surfaces with a fluorinated compound is no more satisfactory than the method of treating with sulfuric anhydride in the case of bottles of low capacity, in particular with a capacity of less than about 50 ml, given that it does not allow a sufficient attack to lower the hydrolytic resistance of these surfaces to a value lower than the maximum value fixed by the standard of the European Pharmacopoeia.

Now, it has now been discovered that by attacking the interior surface of hollow glass objects using fluorinated compounds and using sulfuric anhydride, it has proved possible to unexpectedly obtain , by a synergistic effect of the two treatments, dealkalized surfaces whose hydrolytic resistance is largely below the maximum values of the standard of the European Pharmacopoeia.

The present invention therefore relates to a process for dealkalizing the interior surface i of hollow glass objects, which is essentially characterized in that this surface is attacked using a mixture of air or oxygen and of a fluorinated compound and using sulfuric anhydride, under conditions of temperature and air flow, of fluorinated compound and sulfuric anhydride, such as the hydrolytic resistance of said attacked and dealkalized internal surface is less than the limit value of the standard of the European pharmacopoeia, as defined above, for the glass objects considered. 1

In the particular embodiment of the process according to the invention, a mixture of air or oxygen and a fluorinated compound is first injected, then sulfuric anhydride into hollow glass objects, such as glass vials, at a high temperature in the installation for manufacturing these vials, for example while they are in motion on a conveyor connecting the machine for forming the vials to an oven or annealing arch for these vials.

According to the peculiarity of the invention, the flasks are heated up to the temperature between the dilatometric softening temperature of the glass and the temperature about 50 ° C. below this dilatometric softening temperature, this temperature being between approximately 560 and 600 ° C and preferably close to 600 ° C, for soda-lime type glass, before successively injecting therein a fluorine compound mixed with air or oxygen, and then sulfuric anhydride, without external supply of water vapor.

It has been found that the pyrolytic decomposition of the fluorinated compound in the presence of air or oxygen gives rise to several secondary compounds whose nature depends on the fluorinated compound used and which attacks the glass in synergy with sulfuric anhydride.

As fluorinated compounds, it is possible to use, in the context of the present invention, the derivatives; fluorinated and optionally chlorinated methane and ethane, such as, for example, difluoroethane (CH ^ -CHFg) or compound 152 A, or dichloro-difluoromethane (CCI2F2) or freon 12.

Depending on the compound chosen, synergy can be provided for example by the formation of a flame in situ which causes a beneficial warming of the skin of the glass, or by the formation of water vapor originating from the pyrolytic decomposition of the compound and its reaction with glass, water vapor which activates the subsequent reaction of sulfuric anhydride, or also by the dealkalization reaction with the chlorine ion which reinforces the subsequent effect of sulfuric anhydride.

According to yet another feature of the invention, the mixture of air and fluorinated compound, such as difluoroethane, contains an excess of air or oxygen.

The volumetric ratio of the fluorinated compound to air is preferably greater than about 1 volume of fluorinated compound per 30 volumes of air. This ratio can, for example, reach 1 to 2.5.

The treatment of the interior surface of hollow glass objects by the process according to the invention is advantageously carried out by means of injectors or nozzles operating discontinuously each time an object to be treated passes opposite these injectors.

The injectors of the mixture of air or oxygen and of fluorinated compound are arranged directly upstream of the sulfuric anhydride injectors above the conveyor bringing the flasks of the forming machine to the furnace or to the annealing arch, the operation of the injectors being advantageously controlled by solenoid valves, the actuation of which is ensured by detection means, such as photoelectric cells, of the passage under the vial injectors on said conveyor.

In the process according to the invention, the sulfuric anhydride can advantageously be prepared in an oven for the catalysis of the oxidation of sulfur dioxide to sulfuric anhydride containing a known oxidation catalyst, this oven being heated and being supplied with sulfur dioxide and oxygen at a flow rate which can be approximately 150 liters per minute, so as to produce sulfuric anhydride at a pressure of approximately 1 kg / cm 2.

The process according to the invention is illustrated by the following tests which have been carried out on an industrial scale.

Glass vials of the soda-lime type, particularly suitable for containing penicillins, having the following characteristics: capacity: 10 ml weight: 16 g height: 46.8 mm diameter of the cylindrical part: 23 mm · '1 diameter of l 'opening: 12.65 mm were processed on a conveyor connecting a forming machine to an annealing furnace. The bottles were cut by the forming machine at a rate of 332 bottles per minute and transported by the conveyor at a speed of 36 cm / second.

Two injectors or nozzles of a mixture of air and difluoroethane followed by two injectors or nozzles of SO ^ were placed at a distance of approximately 20 cm from each other above the endless transporter serving bringing the vials from the forming machine to the annealing furnace. The distance between the free ends of the injectors and the open end of the neck of the vials was about 6 to 7 mm. Upstream of the injectors, the flasks were passed through a heating furnace with radiant burners made of ceramic material of the "Pyronics" type (manufactured by the company Pyronics Inc., Cleveland, USA) supplied with a mixture of natural combustible gas and of air, the oven being equipped with two side burners and two upper burners * supplied with gas at a pressure of approximately 200 grams.

In a first series of tests A, vials were subjected, after reheating to a temperature of about 595 ° C, only to injections (2 injectors) using a mixture of air and difluoroethane (compound 152 A).

In a second series of tests B, flasks were subjected to injections (2 injectors) of sulfuric anhydride (SO 4) obtained by catalytic oxidation of sulfur dioxide using oxygen in the presence of vanadium oxide, without the use of steam.

In a third series of tests C, flasks were subjected to injections of SO 2 and v of dry water vapor at a pressure of approximately 4 kg / cm 2.

In a fourth series of tests D, flasks were subjected, after preliminary reheating to a temperature of about 595 ° C, with injections of SO 2 and water vapor.

In a fifth series of tests E ^, EE ^, E ^ and E ^ by the method according to the invention, flasks previously heated to about 595 ° C, were first subjected to an injection of difluoro-methane ( compound 152 A), then to an injection of SO 2, without external supply of water vapor.

The following table indicates the average of the hydrolytic resistances measured (expressed in ml of 0.01 N HCl / 100 ml of water) according to the aforementioned European standard. The maximum value of hydrolytic resistance for 10 ml bottles is 1 ml of 0.01 N HCl / 100 ml of water.

In all the tests, each vial was subjected either to a double injection of compound 152 A, or to a double injection of SO 2, or successively 1 to a single injection of compound 152 A and to a single injection of SO 2, each injection having a duration of 30 milliseconds corresponding to the time of passage of the opening of the bottle under the injector.

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The preceding table reveals that the injection of fluorinated compound alone, as well as the injection of sulfuric anhydride alone does not make it possible to lower the hydrolytic resistance to a value lower than the maximum value of 1 ml of HCl 0 , 01 N / 100 ml (test series A, B, C, D), for vials with a capacity of 10 ml. On the other hand, when operating in accordance with the present invention (tests E> j to E ^), that is to say by treating the bottles w successively using a mixture of air and fluorinated compound and using SO ^, there is a dramatic decrease in the value of hydrolytic resistance, even in the case where the amount of fluorinated compound is very low (series of tests E ^ and E ^). The above table shows that the process according to the invention makes it possible to reduce the hydrolytic resistance of the treated surface of glass bottles to a value of less than 50% of the maximum limit value of the European Pharmacopoeia standard for the glass objects considered. .

It is obvious that the invention is not limited to the details described above and that numerous modifications can be made to these details without departing from the scope of the invention.

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Claims (10)

1 Process for dealkalizing the interior surface of hollow glass objects, characterized in that this surface is attacked using a mixture of air or oxygen and a fluorinated compound and using 1 sulfuric anhydride, under conditions of temperature and air flow or oxygen / fluorinated compound and sulfuric anhydride such that the hydrolytic resistance of said attacked and dealkalized internal surface is less than the limit value of the standard of the European Pharmacopoeia for the glass objects under consideration. 2. Method according to claim 1, characterized in that first injected a mixture of air or oxygen and a fluorinated compound, then sulfuric anhydride in glass vials at a high temperature included between the dilatometric softening temperature of the glass and a temperature approximately 50 ° C lower than this dilatometric softening temperature. 3. Method according to claim 2, characterized in that glass bottles of the soda-lime type are brought to a temperature between about 560 ° C and 600 ° C. 4. Method according to claim 2, characterized in that first a mixture of air or oxygen and a fluorinated compound is injected, then sulfuric anhydride in vials located in a manufacturing installation of vials between a vial forming machine and an annealing oven thereof. 5. Method according to either of the preceding claims, characterized in that the mixture of air or oxygen and fluorinated compound and sulfuric anhydride is injected by means of injectors or nozzles operating in such a way discontinuous each time the opening of a bottle is located opposite each injector. 6. Method according to either of the preceding claims, characterized in that a fluorinated and optionally chlorinated derivative of methane or ethane is used as the fluorinated compound. 7. Method according to claim 6, characterized in that difluoroethane (CH ^ -Cffi * ^) or dichlorodifluoromethane (Cd ^ Fg) is used as the fluorinated compound. 8. Method according to any one of the preceding claims, characterized in that the mixture of air or oxygen and of fluorinated compound contains a volumetric excess of air or oxygen. 9. Method according to claim 8, characterized in that a mixture of air and fluorinated compound is used, in which the volumetric ratio of the fluorinated compound to air is greater than approximately t 1: 30. 4 · · » \ 10, - Method according to any one of the preceding claims, characterized in that it is applied to glass bottles with a capacity of less than about 100 ml. 11. The method of claim 10, ^ characterized in that it is applied to glass vials * with a capacity of about 5 to 50 ml. \ "