Impregnated filter material

Abstract

A method for manufacturing an impregnated filter material includes preparing at least one impregnating solution comprising sulphate and phosphate; providing a filter material; and impregnating the filter material with at least one impregnating solution, at least once. In this manner, it is possible to manufacture an impregnated filter material for the removal of noxious substances and/or toxins, which includes sulphate and phosphate. The noxious substances and/or toxins can thereby be present in the form of gases and/or vapours.

Claims

1. A method for manufacturing an impregnated filter material, wherein the method comprises the following steps: providing at least one impregnating solution comprising sulphate and phosphate; providing a filter material; and impregnating the filter material with at least one impregnating solution, at least once; wherein the filter material is an activated carbon manufactured from coconut husks.

2. The method according to claim 1, wherein at least one impregnating solution comprises molybdenum and/or copper and/or zinc.

3. The method according to claim 1, wherein the impregnating solution is an aqueous solution.

4. The method according to claim 1, wherein the method further comprises the step of: drying the filter material after an impregnation.

5. The method according to claim 1, wherein at least one impregnating solution comprises at least one of the following impregnating chemicals: sulphuric acid and phosphoric acid.

6. The method according to claim 1, wherein at least one impregnating solution comprises at least three of the following impregnating chemicals: water, ammonia, nitrate, copper salt, ammonium carbonate, molybdenum salt, halogenate, zinc salt, sulphate, phosphate, and/or triethylene diamine (TEDA).

7. The method according to claim 1, wherein the impregnating solution and/or the impregnating solutions comprise at least one of the following impregnating components: phosphate, sulphate, molybdenum, zinc and copper.

8. The method according to claim 1, wherein the method further comprises the steps of: providing a zinc chloride solution; impregnating the filter material with the zinc chloride solution.

9. The method according to claim 1, wherein the impregnated filter material produced by the method includes: 1-12% by weight of zinc sulphate, 0.5-3.5% by weight of zinc phosphate, 0.5-5% by weight of ammonium heptamolybdate, one or both of a) 1-15% by weight of zinc hydroxide, and b) 1-15% by weight of zinc carbonate, 0.02-2% by weight of silver oxide, 0.1-2% by weight of TEDA, 0.5-2% by weight of potassium iodate, and 0.5-6% by weight of copper oxide.

10. An impregnated filter material for the removal of noxious substances and/or toxins out of respiratory air, wherein the impregnated filter material comprises sulphate and phosphate, and wherein the filter material is an activated carbon manufactured from coconut husks.

11. The filter material according to claim 10, wherein the impregnated filter material comprises molybdenum, copper and zinc.

12. The filter material according to claim 10, wherein the filter material is manufactured by a method including: providing at least one impregnating solution comprising sulphate and phosphate; providing a filter material of activated carbon manufactured from coconut husks; and impregnating the filter material with at least one impregnating solution, at least once.

13. The filter material according to claim 10, wherein the filter material comprises zinc sulphate, zinc phosphate, molybdate and/or zinc carbonate.

14. The filter material according to claim 10, wherein the filter material comprises silver, triethylene diamine (TEDA), halogenate and/or copper.

15. The filter material according to claim 10, wherein the filter material comprises: 1-12% by weight of zinc sulphate, 0.5-3.5% by weight of zinc phosphate, 0.5-5% by weight of ammonium heptamolybdate, one or both of a) 1-15% by weight of zinc hydroxide, and b) 1-15% by weight of zinc carbonate, 0.02-2% by weight of silver oxide, 0.1-2% by weight of TEDA, 0.5-2% by weight of potassium iodate, and 0.5-6% by weight of copper oxide.

16. A filter for removing noxious substances and/or toxins from respiratory air, comprising a filter material according to claim 10.

17. A respiratory protective mask and/or respiratory air protective device comprising a filter according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject-matter of the invention is explained in more detail by way of preferred embodiment examples which are represented in the accompanying drawings. In each case shown schematically are:

(2) FIG. 1 NH.sub.3 desorption according to Swiss specifications for ABC protective filters TPH-07 for filter material with a mesh size of 1430;

(3) FIG. 2 NH.sub.3 desorption according to Swiss specifications for ABC protective filters TPH-07 for filter material with a mesh size of 716;

(4) FIG. 3A flow diagram of a test apparatus for testing filter material; and,

(5) FIG. 3B schematic construction of a test apparatus for testing filter material.

DETAILED DESCRIPTION OF THE INVENTION

(6) Basically, the same parts are provided with the same reference numerals in the figures.

(7) The following results could be achieved in various tests, in a performance comparison of products of the company Dr.P.Pleisch AG which have been obtainable on the market for some time now, specifically of the chromium-containing activated carbon PLW K and of the chromium-free activated carbon PL MC M (similar to that described in EP 1877338), with the product according to the invention, also characterised as PL MC C_CBRN.

(8) Favourable ClCN Conversion by Way of Phosphates

(9) An important warfare agent is cyanogenic chloride (ClCN) which must be adsorbed by the filter material. Long holding (withstanding) times counter to this warfare agent are demanded in most ABC protective filter specifications. As is evident from Table 1, it is indeed the phosphate which helps to prevent or minimise the ageing of the active carbon with regard to cyanogenic chloride. Two PL MC C_CBRN impregnated filter materials according to the invention and with variable impregnations (see Table 1) were used for the ageing test with regard to cyanogenic chloride, under the following test conditions:

(10) Pre-Conditioning of the Sample:

(11) Before the test, the impregnated filter material is pre-moistened in a testing tube with an airflow of 5.9 cm/s, 80%2% relative humidity and 221 C., until equilibrium. The activated carbon is thereafter stored in the open testing tube for 7 days at 46 C. The activated carbon is again pre-moistened with an airflow of 5.9 cm/s, 80%2% relative humidity and 221 C. until equilibrium, and tested.

(12) Test Conditions of the Cyanogenic Chloride Test:

(13) A 20 mm activated carbon bed is filled into a testing tube of 50 mm diameter by way of snow-storm filling. The cyanogenic chloride test concentration lies at 4000 mg/m.sup.3 in an airflow of 6.95 L/min (linear speed 5.9 cm/s). The relative humidity of the airflow is 802% and the air temperature is 243 C. The testing was continued until the breakthrough of 2.5 mg/m3 is reached.

(14) The presence of phosphates on the impregnated filter material favours the conversion of cyanogenic chloride on moistened filter material after a thermo-loading or with long service lives >100 days. The impregnated filter material undergoes a reduced ageing against cyanogenic chloride. ABC protective filters as are applied e.g. in Israel for the protection of the population can be applied and manufactured more effectively and efficiently by way of this.

(15) TABLE-US-00002 TABLE 1 Ageing with regard to cyanide, of the PL MC C:CBRN, with a different composition. theoretical content [%] activated Zn Cu Mo KIO.sub.3 Zn SO.sub.4.sup.2 PO.sub.4.sup.3 ClCN.sub.aged holding carbon type [%] [%] [%] [%] [%] [%] [%] time [min] PL MC 8.3 >0.5 >0.5 2.1 1.5 1.3 0.4 31 C_CBRN 1 PL MC 8.3 >0.5 >0.5 2.1 1.5 1.3 0.6 42 C_CBRN 2
Comparative Results

(16) In contrast to the filter material type PL MC C, the impregnated filter material PL MC C_CBRN according to the invention has the same or similar characteristics to the chromium-containing type PLW K. Various test results for various test conditions are compared hereinafter.

(17) ABC Protective Filter Testing Standard

(18) Pre-conditioning of the sample initial and aged:

(19) Before the test, 1602 mL of filter material is moistened in a testing tube of 100 mm diameter with an airflow of 30 L/min, 80%2% relative humidity and 231 C. for 48 h. The impregnated filter material is subsequently used for the initial test. In contrast to this, for the aged test, the impregnated filter material is additionally stored in a closed testing tube for 96 h at 50 C. and subsequently used for the aged test.

(20) Test Conditions:

(21) The pre-conditioned, impregnated filter material is now individually tested against cyanogenic chloride, hydrocyanic acid and chloropicrin. The test concentrations of the individual test substances lie at 2000 mg/m.sup.3 test air. The test airflow lies at 30 L/min (contact time 0.32 s). The relative humidity of the airflow is 80%2% and the air temperature is 231 C. The test was carried out until the breakthrough of 5 mg/m.sup.3 is reached. The respective results are summarised in Table 2.

(22) TABLE-US-00003 TABLE 2 Holding times of PLW K, PL MC C and PL MC C_CBRN for different ABC protective filter test substances in an initial test and ageing test. PL MC requirement test gas PLW K PL MC C C_CBRN in min chloropicrin holding 96 min 18.8 min 77.3 min 60 time initial chloropicrin holding 91 min n.b. 70.7 min 50 time aged cyanogenic chloride 115 min 29 min 95 min 60 holding time initial cyanogenic chloride 75 min 43 min 66.3 min 40 holding time aged hydrocyanic acid 82.3*/100** min 51** min 59*/62.3** min 50*/50** holding time initial (no di-cyanide) hydrocyanic acid 48.7*/>56** min 50** min 44.7*/45.7** min 35*/35** holding time aged (no di-cyanide) *di-cyanide breakthrough **hydrocyanic acid breakthrough

(23) As is evident from Table 2, the product PL MC C (chromium-free filter material) does not meet the requirements. However, the impregnated filter material according to the invention meets the requirements.

(24) ABC Protective Filter Test Standard Combined with the Standard for Industrial Filters (EN14387)

(25) For a filter which until now has been filled with a chromium-containing activated carbon (PLW K), a chromium-free activated carbon must developed and should replace the chromium-containing filter material. Thereby, the filter should meet the demands of the ABC protective filter standard and EN14387 Class 2. EN14387 is a European standard for the testing of industrial person protective filter materials. Only the impregnation described hereinafter can be used for such a filter material: additionally zinc chloride (ZnCl.sub.2) moistened in the region of 8-12% (W/W) with water, until the water content lies between 8-12%, as is represented in Table 3. Three filter materials are compared with one another hereinafter.

(26) TABLE-US-00004 TABLE 3 Additional impregnating components for different impregnated filter materials. zinc chloride content filter material [%] water content [%] PLW K-ZnCl.sub.2 8.5 10.0 PL MC C_CBRN-ZnCl.sub.2 8.5 10.0 PL MC C-ZnCl.sub.2 8.5 10.0

(27) Testing according to ABC protective filter test standard carried out as follows:

(28) Pre-Conditioning of the Sample Initial:

(29) Before the test, 4005 mL of the impregnated filter material is moistened in a testing tube of 100 mm diameter with an airflow of 30 L/min, 90%2% relative humidity and 181 C. for 48 hours. The activated carbon is subsequently used for the initial test. In contrast to this, for the aged test, the impregnated filter material was additionally stored in a closed testing tube for 96 hours at 50 C. and subsequently used for the aged test.

(30) Test Conditions:

(31) The pre-conditioned, impregnated filter material, similarly as with the filter material free of zinc chloride described above, is now individually tested against cyanogenic chloride, hydrocyanic acid and chloropicrin. The test concentrations of the individual test substances lie at 2000 mg/m.sup.3 test air. The test airflow lies at 30 L/min (contact time 0.8 s). The relative humidity of the airflow is 90%1% and the air temperature is 181 C. The test is continued until the breakthrough of 5 mg/m.sup.3 is reached.

(32) As is evident from Table 4, the filter material PL MC C_CBRNZnCl.sub.2 has a reduced ageing with regard to HCN, as the initial chromium-containing filter material PLW KZnCl2.

(33) TABLE-US-00005 TABLE 4 Holding times of PLW K-ZnCl.sub.2, and PL MC C_CBRN-ZnCl.sub.2 for different ABC protective filter test substances in an initial test and an ageing test. PL MC C_CBRN- test gas PLW K-ZnCl.sub.2 ZnCl.sub.2 requirement in min chloropicrin >120 min 220 min 60 holding time initial chloropicrin >120 min 245 min 50 holding time aged cyanogenic chloride >120 min 217 min 60 holding time initial cyanogenic chloride >120 min 152 min 40 holding time aged hydrocyanic acid >120*/>120** min 132*/148** min 60*/60** holding time initial hydrocyanic acid 83*/131** min 110*/145** min 50*/50** holding time aged *di-cyanide breakthrough **hydrocyanic acid breakthrough
Test According to EN14387

(34) Filter materials of the type PL MC C which are impregnated with zinc chloride and have been moistened to a water content of 8-12% (W/W), with test substances such as SO.sub.2 and H.sub.2S have a significant ageing after a thermo-loading. For this reason, the two chromium-free types PL MC C and PL MC C_CBRN are compared amongst one another. The samples are conditioned as follows, in order to simulate the ageing.

(35) Pre-Conditioning of the Sample Aged

(36) 1000 mL of impregnated filter materials are added into a glass vessel and thereafter closed and stored for 10 days at 100 C., before the test. The filter material is subsequently cooled to room temperature and used for the aged test.

(37) Test Conditions:

(38) The pre-conditioned filter materials are filled into a testing tube having 60 mm diameter by way of snow-storm filling. The activated carbon layer is 32 mm. The elaborated, pre-conditioned filter materials are now tested individually against SO.sub.2 and H.sub.2S. The test concentrations of the individual test substances in the testing air lie at 5000 ppm. The testing air flow lies at 9.8 L/min (contact time 0.56 s). The relative humidity of the air flow is 70%5% and the air temperature is 214 C. The test was continued until the breakthrough of 5 ppm for SO.sub.2 or 10 ppm for H.sub.2S is reached.

(39) As is evident from the Table 5, the impregnated filter material PL MC C_CBRN ZnCl2 has a reduced ageing, as is the case with chromium-free activated carbon PL MC C ZnCl2. Hence an improvement with regard to the state of the art could also be achieved here.

(40) TABLE-US-00006 TABLE 5 Holding times of PL MC C_CBRN-ZnCl.sub.2 and PL MC C-ZnCl.sub.2 for SO.sub.2 and H.sub.2S. SO.sub.2 holding time H.sub.2S holding time activated carbon type after ageing [%] after ageing [%] PL MC C_CBRN-ZnCl.sub.2 93 82.9 PL MC C-ZnCl.sub.2 78.9 57.1
Swiss Specification for ABC Protective filter TPH-07

(41) The filter material from the state of the art PL MC C has very good gas holding times at high contact times and high test concentrations. The new filter material according to the invention can also be applied with high contact times. The respective results are summarised in Table 6.

(42) Preconditioning of the Sample (F) and (FAN):

(43) 1520/+2 mm of impregnated filter material is moistened in a testing tube of 60 mm diameter with an airflow of 16.31.63 L/min, 90%0/+5% relative humidity and 200.5 C. for 60 hours before the testing. The activated carbon is subsequently used for the (F)-test. In contrast to this, the impregnated material was additionally stored in the closed testing tube for 100 days at 20 C. and subsequently used for the (FAN)-test

(44) TABLE-US-00007 TABLE 6 Holding times of PLW K, PL MC C and PL MC C_CBRN for different ABC protective filter test substances in an (F)-test and a (FAN) test. PL MC test gas PLW K PL MC C C_CBRN requirement chloropicrin >160 min >170 min *215 min >50 min holding time (F) chloropicrin >140 min >190 min 67 min >50 min holding time (FAN) cyanogenic chloride >180 min >180 min *220 min >80 min holding time (F) cyanogenic chloride >140 min >180 min 203 min >80 min holding time (FAN) hydrocyanic acid >120*/>120** min >120** min 113*/>113** min >80*/>80** min holding time (F) hydrocyanic acid >80*/>80** min >110** min 87*/>87** min >80*/>80** min holding time (FAN) *di-cyanide breakthrough **hydrocyanic acid breakthrough
Test Conditions:

(45) The conditioned filter materials (activated carbons) are now tested individually against cyanogenic chloride, hydrocyanic acid and chloropicrin. The test concentrations of hydrocyanic acid and cyanogenic chloride lie at 5 g/m.sup.3 test air and the test concentration of chloropicrin lies at 16 g/m.sup.3. The test airflow lies at 16.31.63 L/min (contact time 1.58 s). The relative humidity of the airflow is 80%2% and the air temperature is 231 C. The testing was continued until a breakthrough of 5 mg/m.sup.3 is reached.

(46) Gas Holding Times Against Phosphine and Nitrogen Dioxide (NIOSH-CBRN Conditions)

(47) The filter materials were tested as delivered. The filter materials are therefore not specifically pre-conditioned.

(48) Test Conditions

(49) The impregnated filter material is filled into a testing tube with a 60 mm diameter by way of snow-storm filling. The testing layer height is 321 mm. The impregnated filter material is tested against phosphine and nitrogen dioxide. The test concentrations of the individual test substances, for phosphine lies at 300 ppm and for nitrogen dioxide at 200 ppm. The test airflow lies at 20.91.5 L/min (contact time 0.26 s). The relative humidity of the air flow is 25%5% and the air temperature is 205 C. The test was carried out until the breakthrough of 0.3 ppm with phosphine and 25 ppm with nitrogen monoxide or 1 ppm nitrogen dioxide (nitrogen dioxide is converted on the activated carbon into nitrogen monoxide.) The respective test results are summarised in Table 7.

(50) TABLE-US-00008 TABLE 7 Breakthrough times of phosphine and nitrogen dioxide for PLW K, PL MC C and PL MC C_CBRN. test gas PLW K PL MC C PL MC C_CBRN requirement phosphine >47.4 min 5.1 min >40.5 min min. 15 min nitrogen 25.4 min 5.0 min 18.4 min min. 15 min dioxide

(51) Since chromium-containing filter materials are forbidden in the USA for example, and the chromium-free filter material PL MC C does not meet the standards, only the impregnated filter material according to the invention can be applied.

(52) Gas Holding Times Against Chlorine Gas

(53) The filter materials were tested as delivered, also for this test. The filter materials are therefore not specifically pre-conditioned.

(54) Test Conditions:

(55) The activated carbons are filled into a testing tube with a 60 mm diameter by way of snow-storm filling. The test layer height is 321 mm. The activated carbons are tested against chlorine. The test concentration lies at 1000 ppm. The test airflow lies at 9.80.5 L/min (contact time 0.554 s). The relative humidity of the airflow is 70%5% and the air temperature is 205 C. The test is continued until the breakthrough of 0.5 ppm of chlorine or 1.0 ppm of formaldehyde. (Chlorine reacts with TEDA (tetraethylene diamine) on the filter material into noxious formaldehyde). The respective test results are summarised in Table 8.

(56) TABLE-US-00009 TABLE 8 Breakthrough times of chlorine for PLW K, PL MC C and PL MC C_CBRN. test gas PLW K PL MC C PL MC C_CBRN chlorine **>90 min *<10 min *>40 min *di-cyanide breakthrough **hydrocyanic acid breakthrough

(57) Filter materials which are impregnated with TEDA and correspond to the type PL MC C have only just and less of the chlorine gas performance, in comparison to the impregnated filter materials according to the invention. Chlorine gas holding times which are as long as possible however are very important, since chlorine gas is indeed often used as a warfare gas.

(58) NH3 Desorption (According to Swiss Standard for ABC Protective Filter Standard TPH-07)

(59) For this test too, the filter materials are tested as delivered. The filter materials are therefore not specifically pre-conditioned.

(60) Test Conditions for 1430 Mesh Size:

(61) The impregnated filter material with the grain size of 1430 mesh size is filled into a testing tube with a 60 mm diameter by way of snow-storm filling. The test layer height is 1521 mm. The samples are then subjected to a test airflow of 14.40.5 L/min (contact time 0.424 s). The test air humidity is 900/+5% and the test air temperature 205 C. The air exiting after the testing tube is tested for ammonia. With the leached-out ammonia, it is the case of the so-called residual ammonia which was not completely expelled from the activated carbon during the drying process. The test was continued until the maximum of the NH3 desorption is achieved or exceeded. The respective test results are shown in FIG. 1. Thereby, the data for PL MC C_CBRN are represented as a solid line, for PL MC C as a dashed line and for PLW K as a dotted line. It is evident from FIG. 1, that PL MC C_CBRN has the lowest ammonia desorption (NH3-des).

(62) Test Conditions for 716 Mesh Size:

(63) The impregnated filter material with the grain size of 716 mesh size is filled into a testing tube having a 60 mm diameter by way of snow-storm filling. The test layer height is 1521 mm. The samples are then subjected to throughflow with a test airflow of 16.30.5 L/min (contact time 1.58 s). The test air humidity is 90%0/+5% and the test air temperature is 202 C. The air which has exited after the testing tube is tested for ammonia (NH3). The ammonia which was leached out of the activated carbon with this test is present in a bonded form after manufacture of the activated carbon. The test was carried out until the maximum of the NH3 desorption is reached or exceeded. The respective test results are represented in FIG. 2. Thereby, the data for PL MC C_CBRN are represented as a solid line, for PL MC C as a dashed line and for PLW K as a dotted line. It is evident from FIG. 2 that PL MC C_CBRN has a similarly large or high ammonia desorption (NH3-Des) as PLW K and PL MC C.

(64) FIGS. 3A and 3B show a test apparatus for the testing of impregnated filter material, as described beforehand. FIG. 3A thereby shows a flow diagram and FIG. 3B the schematic construction. On testing, compressed, dry air (A) is closed-loop controlled with a mass-flow controller (B) for setting the test volume flow. This is led through a temperature-controllable water bath (C) for processing the relative humidity and a controller (D) is configured for setting the desired relative humidity. A measuring appliance (E) serves for determining the relative humidity. A gas bottle (F) with the agent to be tested (for example NH3, PH3, NO2 or Cl2) is connected to a mass-flow controller (G) for setting the desired target concentration. A mixing chamber (H) is provided, in order to mix the agent with the processed air. The filter material to be tested is arranged in the testing tube (I), and a gas detector (J) serves for measuring the gas breakthrough.