FI76257C - SAETT FOR STERILIZATION WITH FORMALIN. - Google Patents

Description

7625 7

Sterilization method using formalin

The present invention relates to a method for sterilizing goods in an autoclave under a formaldehyde and water vapor atmosphere, wherein in each sterilization treatment the goods are placed in an autoclave chamber which is evacuated by impinging vacuum and steam to an intermediate pressure to preheat the autoclave.

Formaldehyde is a toxic and easily reactive gas that can cause allergic problems in people who come into contact with a product containing the gas. The use of formaldehyde as a disinfectant in various fields of application has long been known. Formaldehyde is gaseous at room temperature and is readily soluble in water. In practice, therefore, formalin, which is about 40% aqueous formaldehyde, is used. Since the early 1960s, there have been methods that even allow sterilization with formaldehyde.

Steam sterilization alone is an old method which involves treating the product at temperatures of about 110-140 ° C. However, there are many products that cannot withstand processing at such high temperatures, and therefore other sterilization methods and media have been sought. Here, formalin autoclaves open up new possibilities. Theoretically, with such an autoclave, a sterile product can be obtained by treatments at about 80 ° C. In practice, however, it has been found that sterility can be achieved, but at the same time both formaldehyde residues and a paraformaldehyde coating on the product are obtained. The amounts of such gas residues remaining in the sterilized product vary widely in different treatments, which is also a drawback and also shows that the method used is not ideal.

It has been found that a 40% aqueous solution of formaldehyde can be used. By adding 16 ml of such a solution per liter of autoclave 100 2 7625 7, a good sterilization efficiency has been achieved in the temperature range 60-80 ° C, but there are still residues in the product.

The above-mentioned drawbacks can be eliminated by using the present method, which is mainly known from what is set forth in claim 1.

The invention will be explained in more detail below with reference to, for example, a selected autoclave and shown in the drawings. Figure 1 shows a simplified diagram of an autoclave using formalin and steam. Figure 2 shows on an enlarged scale a part of Figure 1 with a formalin evaporator. Figure 3 shows the pressure curve of the autoclave during processing.

The autoclave of Figure 1 has a chamber 10 with a door and jacket 11 not shown, with two connections 12, 13 at the bottom for a line 14, a circulation pump 15 and a water heater 16. The jacket has a partition wall 17 between the connections 12, 13 at the bottom. and the circulation line 14 has a heat transfer medium, for example water, which is heated by an electric heater 18 to a temperature determined by a thermostat 19 from which the line 20 leaves the sensor 21 of the jacket 11.

The treatment medium is fed to the autoclave chamber 10, e.g. from an inverted bottle 22, which contains a dose of formalin suitable for treatment. From the bottle 22 comes a line 23 with a solenoid valve 24 to the evaporator 25. The valve 24 is controlled by a programming device 27. The bottle 22 has a rubber seal and the line 23 has a needle-like tip.

The evaporator 25 consists of a U-tube 28, one branch 29 of which is connected to a formalin line 23 and the other branch 30 is connected to a supply line 31 leading to two autoclave chamber inlets 32. Inside each inlet there is a plate 33 which distributes the fed treatment medium to the chamber. The U-tube li 3 76257 28-30 is provided with heating means, in the example of which there is a steam-heated jacket 34. A supply line 35 with a branch line 36 with a manometer 37 leaves the line 38 to an inlet 39 at the top of the steam jacket 34. The line 38 has a solenoid valve 40 controlled by the programming device 27. The supply line 31 is provided along its entire length with a heating element, indicated by a broken line 41, which may be an electric heater or a steam line.

From the bottom of the steam jacket 34 leaves a condensate drain line 42 which passes through a steam trap 43 and a solenoid valve 44 controlled by a programming device 27, after which it passes through a condenser 45 to an outlet line 46 which removes condensate from the outlet 47.

The condenser 45 is cooled by water from a water line 48 passing through a coil 49 in the condenser, after which it is discharged through an outlet 46. In addition, an outlet line 50 passes through the condenser from the bottom of the chamber 10. The line 50 is provided with a solenoid valve 51 connected to the programming device 27. After passing through the condenser 45, the outlet line 50 passes through a vacuum pump 52 to which, like the condenser, water is supplied from the line 48 via a line 53. The vacuum pump 52 is connected to the outlet 47 by an outlet line 54.

The steam supply line 35 has a water purifier 55, which may be a cyclone purifier, so that the line contains anhydrous steam which is passed through a line 57 with a solenoid valve 56 to the formalin line 23 before the evaporator 25. The steam fed to the chamber is thus passed through the evaporator 25 and the heated line.

Once pulses 76-78 have been completed, no ambient air can be admitted to the autoclave because (under vacuum in packages containing the goods) this impure 4 76257 air would penetrate the packages and contaminate the goods therein. Therefore, a supply of sterile air must be performed between pulsations 76-78 and the time of the pressure equalization at which the autoclave can be opened. This sterile air is introduced through the atmospheric air supply line 58. This line includes a sterile filter 59 and a solenoid valve 60 and is connected to a formalin line 23 so that the air supplied to the chamber in the same manner as the supplied steam is taken through the evaporator 25 and the heated line 31 to the chamber inlets 32.

At the left side of the chamber, at the inlet 32, there is a connection for sensors connected by wires 62 to indicating and writing instruments 63 which indicate the pressure, temperature and other characteristics of the chamber atmosphere and which can also be connected to the programming device 27.

In Figure 1, the chamber and its jacket 11 are shown in cross-section. The jacket may have an end and a door, which, like the chamber, is provided with a water-heated jacket. Instead, the door can also be equipped with electric heating. All chamber connections are also heated so that they can be kept at a higher temperature than the chamber atmosphere temperature. This is done with hot water, steam or electricity.

Figure 2 shows on an enlarged scale the evaporator 25 and its nearest connecting lines and the formalin bottle 22. When the formalin line valve 24 is opened, a preformed dose of formalin from the bottle 22 flows down to the branch 29 of the U-tube 28. The entire amount of formalin is transferred at once to the U-tube. be of such a large volume that it can hold well. The jacket 34 surrounding the chute is already preheated above the evaporation temperature by means of steam supplied via line 38. In Figure 1, the evaporator 25 is shown as a U-shaped formalin conduit with a similarly shaped jacket, but in Figure 2, the U-tube 28 is fitted in a jacket 34 surrounding both branches of the tube. When the formalin is heated, evaporation takes place, which produces water vapor and gaseous formaldehyde. The steam generated in the left branch 30 leaves the liquid and is passed through line 31 to chamber 10, while the steam generated in right branch 29 fills the vapor space above line 23 and associated lines 57, 58 leading to valves 24, 56 and 60. Therefore, it is important to minimize this steam space. Here, a vapor pressure develops which compresses the formalin in the right branch 29 to the level 64 at the bottom of the U-tube, where the vapor can penetrate the liquid and rise up through the left branch 30 and then exit through the conduit into the chamber. The liquid in the left branch is then pressed up to level 65. This indicates that the U-tube must be of such a size that even when the liquid is pressed down to the right branch, it cannot rise up into the line 31 and drain into the chamber. In this way, a liquid pocket is formed in the evaporator, thanks to which only pure water vapor and gaseous formaldehyde can enter the chamber.

After the formalin evaporates and enters the chamber, steam is fed into the chamber. Steam is then passed through line 57 and U-tube 29, 30 before being fed through line 31 into the chamber. In this way, additional heat is supplied to the evaporator and any formalin residues in the U-tube are evaporated and introduced into the chamber with the steam.

The method is as follows when the products are sterilized with formalin in an autoclave.

The product is placed in chamber 10 and the chamber door is closed. In this case, the chamber contains air from the product and the atmosphere at approximately ambient temperature and pressure. This corresponds to point 0 in Figure 3, which shows the pressure variation in the autoclave chamber as a function of time during sterilization. The jacket of the chamber 10 is heated, if not already preheated, by starting the circulation pump 15 and the heater 16. When the sterilization temperature is reached, the vacuum pump 52 is started and the pressure in the chamber 10 is reduced, as shown by the line 70 in the curve.

When the desired vacuum is reached, steam is introduced into the chamber according to line 71, so that a temperature of about 80 ° C is obtained in a vacuum of about 50%. This state is maintained for a certain period of time, about 1 minute, shown by line 72. Thereafter, the vacuum suction and the steam supply are repeated a few times with the prescribed holding. These pulses are very important. On the one hand, air is removed from the chamber and the product, and on the other hand, steam is introduced which has to some extent condensed on the surface of the product and to some extent raises the temperature of the product. The amount of condensed moisture is not very large, but it is important because it changes the subsequent formaldehyde treatment. Absolutely dry bacteria do not die at low processing temperatures, at least not in a short time. Moisture dissolves any salt formations, crystals or blood debris in the product and also provides some moisture to existing bacteria. Because formaldehyde is easily soluble in water, it reaches and affects bacteria in the next treatment.

The preconditioning described above has been found to be sufficient even in the more difficult handling case of current packaging types and spore samples, i.e. when the sterilization process is operated with a minimum load on the chamber 10. This case is the most demanding because the radiation from the chamber wall heats a small amount of product in the chamber to such a high temperature that condensation of steam becomes more difficult.

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Holding times with steam at about 80 ° C or a delay before the next vacuum during pulsation result in the product being preheated to 80 ° C so that the steam can penetrate and, on the one hand, condense and, on the other hand, raise the temperature of the product. This gives better microbiological efficiency during sterilization, handling. Thanks to this improved wetting step, which is fully controlled and can be repeated in each treatment, less formaldehyde can be added than previously thought possible. Nevertheless, the right bacteriological destruction effect is achieved. It has been found that the amount of formalin used can be reduced to almost a quarter of the amount previously used. An interesting consequence of this fact is that the residues of undesired substances in the sterilized product are much lower. This means that by applying the invention, the residual amounts can be removed during the post-treatment of the product to such an extent that the product ready for practical use can be considered to be free of residual amounts.

After pretreatment and when there is a vacuum in the chamber 10, formalin is introduced into the evaporator U-tube 29, 30 and about 110 ° C through line 38 to the evaporator jacket 34. Formalin is evaporated and anhydrous vapor and gaseous formaldehyde free of undesirable and fed into the chamber during a short period 73. This will increase the pressure somewhat. After a short wait 74, water vapor 75 is introduced to a desired treatment pressure of about 50% vacuum at about 80 ° C in chamber 10. This condition is maintained for about 10 minutes and is automatically controlled by programmer 27 by supplying some some steam.

The preconditioning described above and the supply of formalin provide an excellent guarantee that each treatment results in the sterility of the treated product.

After the sterilization cycle, a post-treatment is performed, i.e. according to the invention several pulsations are performed, each of which means that the vacuum pump 52 is started during the cycle 76, supplying condenser 45 with water 48 and valve 51 open so that the chamber gas sucked through the condenser is condensed and fed to the outlet. 47 in liquid form. The steam is then re-introduced into the chamber during cycle 77. It is important, 7625 7 8, that the space after the supply of steam be maintained for a short period 78. After that, repeat the vacuum and steam supply with the specified grip drank a few times. The steam fed in this way is caused to penetrate the product in the chamber each time, whereby it, together with formaldehyde, is sucked out during the next vacuum. This after-treatment is, of course, facilitated by the fact that the treatment has been carried out with a lower amount of formalin per liter of chamber volume than before. However, it has been found that the post-treatment described herein results in a better cleaning and a more reproducible result. However, it has also been found that both the after-treatment time and the number of pulses are important for the result. When the post-treatment is performed in about 10 minutes and with six pulses, the most efficient cleaning process is achieved. A lower or higher heart rate will give a worse result.

The method described not only results in small amounts of residues, but is also interesting in another way. Namely, during the sterilization step 75 ', it can be seen that the gas phase of the chamber contains a significantly higher percentage of formaldehyde than has previously been the case. This affects not only the residue levels but also the sterilization efficiency during treatment.

After the post-pulsations 76-78 have been performed and a vacuum exists in the autoclave, sterile air is introduced through line 58 and evaporator 25 into chamber 10 to provide a pressure slightly greater than the treatment pressure. The vacuum pump 52 is kept running at the same time. The pressure rise is indicated by period 79 in Figure 3. During period 80, the vacuum pump runs while sterile air is added (and is sucked out by the vacuum pump) to flush out any residual formaldehyde. During cycle 80, a pressure is generated that depends on the capacity of the vacuum pump (line 58 is not closed separately when solenoid valve 60 is open) and the permeation resistance of sterile filter 59. The vacuum pump is then stopped (right end of line 80), allowing the flow of sterile air into the autoclave to continue (line 81) until the pressure is equalized (the autoclave has the same pressure as outside it) and the autoclave can be opened. When the process is complete, the door can be opened and the product removed manually for immediate use or storage.

Claims (8)

10 7625? A method for sterilizing goods in an autoclave in a formaldehyde and water vapor atmosphere, wherein in each sterilization treatment the article is placed in an autoclave chamber (10) which is evacuated by impinging vacuum and steam to an intermediate pressure (72), the article being preheated that after preheating, a certain amount of formalin is converted in the evaporator (25) by supplying heat to a gas consisting of water vapor and formaldehyde, and said water vapor and formaldehyde gas is then passed through lines (31, 32) to the autoclave chamber (10) under vacuum; 31, 32) the temperature is kept higher than the atmospheric temperature of the chamber (10) to maintain the chemical composition and gas form of formaldehyde throughout the feed path from the evaporator (25) to the chamber (10), and that a controlled steam supply then provides a sterilization space to sterilize exposing it to formaldehyde and water vapor above room temperature for a time sufficient to sterilize the goods, after which the chamber (10) is evacuated and steam purged by subjecting it several times to vacuum and subsequent steam supply to intermediate pressure (78), the purge and purge ), the vapor pressure (78) is maintained for a period of time before the next vacuum. Process according to Claim 1, characterized in that the rinsing process after the formaldehyde treatment is carried out at least four or at most seven times. Process according to Claim 1, characterized in that the vacuum treatment and the supply of steam after the formaldehyde treatment are carried out five times. Il 7625 7 A method according to claim 1, characterized in that the outlet line (50) connected to the chamber (10) is maintained at a temperature higher than the atmospheric temperature of the chamber (10). A method according to claim 1, characterized in that water is optionally removed from the steam fed to the chamber (10) before it is introduced into the evaporator (25). Method according to Claim 1, characterized in that the air introduced into the chamber (10) after treatment is passed through an evaporator (25) and a steam line (31, 32). 1. A method for sterilizing the autoclaves in an autoclave with an atmosphere of formaldehyde, including a color sterilizing solution in an autoclave chamber (10), evacuating the genome by pulsation with a vacuum and an opening for the cell (72), colors autoclaved chambers (10) of an anhydrous chamber, which can be used for the preparation of formalin and fork (25) genomic colors for the treatment of gas, with the addition of water and formaldehyde, and the presence of genomic gases (31, 32) (10) under vacuum, varying the temperature and gas content (31, 32) of the genome color temperature to the chamber temperature of the gas chamber (25) to the gas chamber (10) och att därefter genom reguller angtill-försel ett steriliseringstillständ ästadkomms, vid vilket det för sterilisering avsedda godset utsätts för forma ldehyd och vattenanga vid en temperatur överstigande rummets för en tid tillräcklig för att sterilisera godset, varefter chamber (10) -78) for