A PROCESS FOR STERILIZATION TREATMENT USING A RESIDUE-FREE HYDROGEN PEROXIDE

Abstract

A process for sterilization or disinfection treatment includes: a) obtaining a hydrogen peroxide vapour from an aqueous hydrogen peroxide solution having a dry residue determined at 105? C. of at most 5 ppm and a total content of Fe, Cr, Mn and Ni in the solution of at most 6 ppb as determined by ICP-MS analysis; and b) treating an object to be sterilized or disinfected with the hydrogen peroxide vapour obtained in a).

Claims

1. A process for a sterilization or disinfection treatment, the process comprising: a) obtaining a hydrogen peroxide vapour from an aqueous hydrogen peroxide solution containing no stabilizer and having a dry residue determined at 105? C. of at most 5 ppm and a total content of Fe, Cr, Mn and Ni in the aqueous hydrogen peroxide solution of at most 6 ppb as determined by ICP-MS analysis; b) sterilizing or disinfecting an object with the hydrogen peroxide vapour obtained in step a).

2. The process according to claim 1, wherein the dry residue determined at 105? C. from the aqueous hydrogen peroxide solution is below the level detectable by CP-MS analysis.

3. The process according to claim 1, wherein a total content of all non-volatile hydrogen peroxide stabilizers present in the aqueous hydrogen peroxide solution is at most 1 ppm.

4. The process according to claim 1, wherein the total content of Fe, Cr, Mn and Ni in the aqueous hydrogen peroxide solution is at most 4 ppb, as determined by ICP-MS analysis.

5. The process according to claim 1, wherein the Cu content in the aqueous hydrogen peroxide solution is at most 0.2 ppb, as determined by ICP-MS analysis.

6. The process according to claim 1, wherein the content of all metals in the aqueous hydrogen peroxide solution is at most 20 ppb, as determined by ICP-MS analysis.

7. The process according to claim 1, wherein the aqueous hydrogen peroxide solution has an active oxygen loss of no more than 4 wt-%, as determined after heating the aqueous hydrogen peroxide solution for 24 hours at 100? C. in a glass vessel.

8. The process according to claim 1, wherein the aqueous hydrogen peroxide solution is suitable for storing for at least four days in an appropriate stainless steel or aluminium container at 20-30? C. temperature with a peroxide concentration drop of less than 0.1 wt %.

9. The process according to claim 1, wherein the aqueous hydrogen peroxide solution has a pH of 2.0-4.5.

10. The process according to claim 1, wherein the aqueous hydrogen peroxide solution is obtained by the anthraquinone process followed by purification thereof by at least one selected from the group consisting of distillation, treatment with ion-exchange resin, and reverse osmosis using a membrane.

11. The process according to claim 1, wherein the aqueous hydrogen peroxide solution contains 10% to 50%, by weight of hydrogen peroxide.

12. The process according to claim 1, wherein the hydrogen peroxide vapor is produced by evaporation or vaporization of the aqueous hydrogen peroxide solution.

13. The process according to claim 1, wherein the object is selected from the group consisting of packaging materials which are optionally beverage and dairy containers, cartons, bottles, caps and other closures; vessels; aseptic and other cold-fill shelf-stable filling equipment and machinery; objects which are optionally fruits or vegetables; medical devices; and contained spaces which are optionally ambulances or rooms.

14. The process according to claim 1, wherein the sterilizing or disinfecting in b) of the process is a vapour aseptic packaging process carried out at a temperature of at least 50? C., of the object.

15. The process according to claim 1, wherein the total content of all non-volatile hydrogen peroxide stabilizers present in the aqueous hydrogen peroxide solution is essentially zero or zero.

16. The process according to claim 1, wherein the Cu content in the aqueous hydrogen peroxide solution is at most 0.1 ppb.

17. The process according to claim 1, wherein the aqueous hydrogen peroxide solution has an active oxygen loss of no more than 2 wt-%, as determined after heating the aqueous hydrogen peroxide solution for 24 hours at 100? C. in a glass vessel.

18. The process according to claim 1, wherein the aqueous hydrogen peroxide solution has a pH of 3.0-4.0.

19. The process according to claim 1, wherein the aqueous hydrogen peroxide solution contains 30% to 40%, by weight of hydrogen peroxide.

20. The process according to claim 1, the process further comprising: storing the aqueous hydrogen peroxide solution for at least four days in a stainless steel or aluminium container at 20-30? C. temperature with a peroxide concentration drop of less than 0.1 wt %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG. 1 shows dry residue obtained after evaporation of 100 g of an unstabilized residue-free hydrogen peroxide solution according to the invention (sample #1).

[0057] FIG. 2 shows dry residue obtained after evaporation of 100 g of a commercially available stabilized premium hydrogen peroxide solution for H.sub.2O.sub.2 vapor applications.

EXAMPLES

Example 1

[0058] Samples #1-#7 of 35% wt % unstabilized hydrogen peroxide solutions with low metal contents were prepared by the known from the prior art purification methods of hydrogen peroxide solution prepared from the anthraquinone process, such as by ion-exchange resin treatment, distillation and/or reversed osmosis.

[0059] The decomposition rate of 35% wt % unstabilized hydrogen peroxide solutions in HDPE bottles with a vented cap at room temperature (20? C.) was measured by determining the assay drop and the H.sub.2O.sub.2 loss. The assay drop was the differential decrease of hydrogen peroxide concentration after 30 days. the H.sub.2O.sub.2 loss was the decrease of hydrogen peroxide in 100% basis from 100 g of the test solution after 30 days. The dependence of the hydrogen peroxide decomposition rate on impurity concentrations can be seen from the comparison of the test results in Tables 1a and 1b.

TABLE-US-00001 TABLE 1a Impurity effect on decomposition rate of H.sub.2O.sub.2 solutions with the low impurity level. Assay H.sub.2O.sub.2 Metals Impurities in H.sub.2O.sub.2 Solutions, ppb Samples drop Loss, g Cu Cr Fe Mn Ni Total #1 ?0.02% ?0.02 0.00 1.29 0.12 0.01 0.06 1.48 #2 ?0.03% ?0.03 0.00 1.24 0.09 0.00 0.03 1.36 #3 ?0.03% ?0.04 0.00 1.11 0.07 0.00 0.01 1.19 #4 ?0.02% ?0.03 0.00 0.59 0.15 0.01 0.05 0.80 #5 ?0.02% ?0.03 0.01 1.05 0.34 0.03 0.22 1.64 #6 ?0.01% ?0.04 0.00 0.75 0.13 0.01 0.06 0.95 #7 ?0.01% ?0.04 0.00 0.63 0.06 0.00 0.01 0.70

Comparative Example 1

[0060] Samples #8-#14 of 35% wt % unstabilized hydrogen peroxide solutions with higher metal contents were prepared by the known from the prior art purification methods of hydrogen peroxide solution prepared from the anthraquinone process by ion-exchange resin treatment, distillation and/or reversed osmosis.

[0061] The decomposition rate of the 35% wt % unstabilized hydrogen peroxide solutions in HDPE bottles with a vented cap at room temperature (20? C.) was measured by determining the assay drop and the H.sub.2O.sub.2 loss after 30 days of storage. The results are summarized in Table 1b.

TABLE-US-00002 TABLE 1b Impurity effect on decomposition rate of H.sub.2O.sub.2 solutions with the higher impurity level. H.sub.2O.sub.2 Assay H.sub.2O.sub.2 Metals Impurities in H.sub.2O.sub.2 Solutions, ppb Sample drop Loss, g Cu Cr Fe Mn Ni Total #8 ?0.18% ?0.22 0.09 3.62 3.91 0.30 2.50 10.33 #9 ?0.22% ?0.27 0.07 1.87 3.31 0.18 1.54 6.90 #10 ?0.16% ?0.19 0.08 2.45 3.13 0.25 1.94 7.77 #11 ?0.16% ?0.20 0.13 3.30 3.22 0.29 2.39 9.20 #12 ?0.23% ?0.28 0.07 2.17 4.06 0.20 1.62 8.05 #13 ?0.32% ?0.39 0.09 3.10 4.85 0.31 2.50 10.76 #14 ?0.35% ?0.40 0.07 2.07 4.21 0.21 1.59 8.08

[0062] It can be seen from the results that increase in the metal impurity level of the unstabilized H.sub.2O.sub.2 solutions from the samples in Table 1a to those of Table 1b led to a significant increase in the decomposition rate of the latter samples.

Example 2

[0063] The starting hydrogen peroxide solution for sample #6 was stored in HDPE bottles with a vented cap under three different temperatures: 20, 35 and 50? C., respectively. The decomposition rates of these unstabilized hydrogen peroxide solutions (samples #15-20) at the specified temperatures were measured in HDPE bottles with a vented cap, for each tested sample twice, by determining the assay drop and the H.sub.2O.sub.2 loss after 1.sup.st 30 and 2.sup.nd 30 days of storage, respectively.

[0064] The results are shown in Table 2. It was observed that there was no problem to store this unstabilized hydrogen peroxide solution under slightly elevated temperature. The hydrogen peroxide concentration after 30 days remained almost unchanged after the storage at 20? C. (positive values of the assay drop), and actually increased under elevated temperatures, due to the evaporation of the solution. H.sub.2O.sub.2 loss even after 30 days of storage at 50? C. was still below 1% (1 g per 400 g) of the solution. The decomposition rates of the peroxide in the second 30 days test was similar to the first 30 days test.

TABLE-US-00003 TABLE 2 Temperature effect on decomposition rates of a H.sub.2O.sub.2 solution (precursor for sample #6) with a low impurity level H.sub.2O.sub.2 Sample #15 #16 #17 #18 #19 #20 Temp. ? C. 20 35 50 Changes in 30 days Wt Loss, g ?0.01 ?0.01 ?0.80 ?1.03 ?3.39 ?3.47 Assay Drop ?0.01% ?0.01% 0.01% 0.03% 0.07% 0.11% H.sub.2O.sub.2 loss, g ?0.04 ?0.06 ?0.25 ?0.23 ?0.88 ?0.77 Changes in another 30 days Wt Loss, g ?0.02 ?0.02 ?0.81 ?1.10 ?3.44 ?3.54 Assay Drop 0.00% ?0.01% 0.01% 0.04% 0.07% 0.10% H.sub.2O.sub.2 loss, g ?0.01 ?0.04 ?0.24 ?0.24 ?0.91 ?0.84

Example 3

[0065] The starting hydrogen peroxide solution for sample #6 was exposed to SS (stainless steel) coupons in glass Kjeldahl flasks. Both glassware and coupons were passivated by following industry's standards. 110 g solution was in contact with each coupon (2?0.5?0.125) at 20? C. initially and the samples were analysed twice: after a 4-days period and then after a 7-days period (total of 11 days). Then the samples (#22a and 22b) were moved into an incubator at 35? C., and kept in it for another 4-days period before a third analysis for the samples.

[0066] Additionally, a stabilized hydrogen peroxide solution sample #21 was prepared by adding 1 ppm of amino tris(methylenephosphonic acid) (ATMP), a common H.sub.2O.sub.2 stabilizer, to the same starting solution as for sample #6 and tested under the same conditions as the unstabilized samples #22a/#22b. Blank samples (the same peroxide solutions to samples #21a/#21b and #22a/#22b but without SS coupons) were also run in parallel as a reference.

[0067] The decomposition rates of the unstabilized samples #22a/#22b and the stabilized samples #21a/#21b at the specified temperatures and times are summarized in Table 3.

TABLE-US-00004 TABLE 3 Stainless steel and stabilizer effect on the decomposition rates of H.sub.2O.sub.2 solutions. Sample Blank Blank to #21 #21a #21b to #22 #22a #22b description with 1 ppm ATMP Unstabilized Decompositions in initial 4 days at 20? C. wt loss, g 0.00 0.00 0.00 0.00 ?0.04 ?0.03 Assay drop 0.01% 0.01% 0.01% 0.01% ?0.04% ?0.06% H.sub.2O.sub.2 loss, g 0.01 0.01 0.01 0.01 ?0.06 ?0.07 Decompositions in next 7 days after initial 4 days at 20? C. wt loss, g 0.00 ?0.02 ?0.03 ?0.03 ?0.09 ?0.12 Assay drop 0.03% ?0.04% ?0.02% 0.03% ?0.24% ?0.22% H.sub.2O.sub.2 loss, g 0.02 ?0.06 ?0.04 0.01 ?0.21 ?0.19 Decompositions in the last 4 days at 35? C. wt loss, g 0.01 ?0.63 ?0.57 ?0.02 ?0.42 ?0.43 Assay drop 0.01% ?1.19% ?1.04% 0.00% ?0.83% ?0.66% H.sub.2O.sub.2 loss, g 0.02 ?1.22 ?1.07 ?0.01 ?0.85 ?0.70

[0068] Stainless steel is the primary construction material for aseptic filling machines. The accumulative contact time of the hydrogen solution with stainless steel in these machines can be up to four days under ambient conditions and even longer.

[0069] When both solutions were in contact with stainless steel coupons, the peroxide solution with 1 ppm ATMP was slightly more stable for the first 11 days under room temperature (20-22? C.). However, after the samples were moved into an incubator and stored for another 4 days at 35? C., the hydrogen peroxide containing 1 ppm ATMP surprisingly started to decompose even faster than the sample without ATMP. The ATMP in the peroxide might promote more metal leaching than stabilizing the metals.

Example 4

[0070] Unstabilized 35% wt % hydrogen peroxide solution (100 g) from the starting solution of sample #6 was slowly evaporated in a Pt crucible according to steps 1-9 of the method described in the description above. Almost no residue could be visually observed in the crucible, as shown in FIG. 1. The residue value was too low to be quantitatively determined (below 2 ppm).

Comparative Example 4

[0071] The residue test described in example 4 was repeated using 100 g of a commercially available stabilized premium hydrogen peroxide solution for vapor applications. A significant amount of a residue was formed from the hydrogen peroxide as can be seen in FIG. 2.

[0072] The presented examples show that the hydrogen peroxide solutions containing no stabilizers, and having a relatively low level of metal impurities, are sufficiently stable during the storage under ambient conditions. They can be handled with regular equipment (SS pumps, meters, pipes) and analysed in a regular lab (no cleanroom is needed). They will produce little residues on evaporation and so they are well suitable for using in evaporation processes, such as sterilization or disinfection treatments with a H.sub.2O.sub.2 vapour, without the need to often remove the dry residue formed after the evaporation.