Apparatus and method for filtration efficiency improvements in fibrous filter media

Abstract

A method for improving air filtration efficiency of a fibrous nonwoven media and a fibrous non-woven air filtration media having improved filtration efficiency. The method includes applying to fibrous material at least about 0.05 wt. % based on a total weight of the fibrous material of chemical treatment comprising an alkoxylated silicone copolymer. The chemical treatment is effective to provide an improvement in an E3 filtration efficiency value of the filtration media as tested according to ASHRAE 52.2 of about 20% or more compared to an E3 filtration efficiency value of fibrous material devoid of any chemical treatment.

Claims

1. A method for improving air filtration efficiency of a fibrous media comprising applying to fibrous material at least about 0.05 wt. % based on a total weight of the fibrous material of chemical treatment comprising an alkoxylated silicone copolymer to provide in improvement in an E3 filtration efficiency value as tested according to ASHRAE 52.2 of about 20% or more compared to an E3 filtration efficiency value of fibrous material devoid of any chemical treatment; wherein the alkoxylated silicone copolymer comprises at least about 80 wt. % of the total amount of chemical treatment applied to the fibrous material.

2. The method of claim 1, wherein the fibrous material comprises fibers selected from the group consisting polyethylene fibers, polypropylene fibers, polyester fibers and bicomponent fibers and blends thereof.

3. The method of claim 1, wherein the fibrous material comprises bicomponent fibers selected from the group of polypropylene/polyethylene terephthalate fibers and polyethylene/polyethylene terephthalate fibers.

4. The method of claims 3, wherein the bicomponent fibers have a cross-section of sheath/core or side-by-side fibers.

5. The method of claim 1, further comprising forming filter media from the treated fibrous material using a dry laid nonwoven process.

6. The method of claim 1, wherein the chemical treatment is applied to the fibrous material by a process selected from the group consisting of spraying the fibrous material with the chemical treatment, dipping the fibrous material in a vessel containing the chemical treatment, and applying the chemical treatment as foam to the fibrous material.

7. The method of claim 2, wherein an add on weight of chemical treatment ranges from about 0.1 to about 0.5 wt. % based on a total weight of the fibers.

8. The method of claim 1, further comprising forming filter media from the chemically treated fibrous material using a wet laid nonwoven process.

9. The method of claim 8, wherein the chemical treatment is applied to the fibrous material by a process selected from the group consisting of spraying the fibrous material with the chemical treatment, dipping the fibrous material in a vessel containing the chemical treatment, and applying the chemical treatment as foam to the fibrous material.

10. The method of claim 1, wherein the chemical treatment further comprises an antistatic agent selected from the group consisting of a cationic antistatic agent, anionic antistatic agent and a non-ionic antistatic agent.

11. The method of claim 1, wherein an antistatic agent comprise at least about 10 wt. % of the total amount of chemical treatment applied to the fibrous material.

12. The method of claim 1, wherein the chemical treatment is applied to the fibrous material as a staple fiber finish.

13. The method of claim 1, wherein the chemical treatment is applied to the fibrous material as a spin finish to fibers of the fibrous material and the spin finish assists in a carding operation for the fibrous material.

14. Filtration media made by the method of claim 1, wherein the filter media meets at least a Minimum Efficiency Rating Value (MERV) of MERV6 as tested by ASHRAE 52.2.

15. A fibrous non-woven air filtration media comprising fibrous material comprising from about 0.1 to about 0.5 wt. % based on a total weight of the fibrous material of a chemical treatment comprising an alkoxylated silicone copolymer, whereby the non-woven air filtration media has an improvement in an E3 filtration efficiency value as tested according to ASHRAE 52.2 of about 20% or more compared to an E3 filtration efficiency value of fibrous material devoid of any chemical treatment; wherein the alkoxylated silicone copolymer comprises at least about 80 wt. % of the total amount of chemical treatment applied to the fibrous material.

16. The filtration media of claim 15, wherein the filtration media is supported or is self-supporting.

17. The filtration media of claim 15, wherein the fibrous material is chemically treated prior to forming the fibrous non-woven air filtration media.

Description

DETAILED DESCRIPTION

(1) As described in more detail herein, a chemical treatment is applied to the fibers of a nonwoven filter media that provide a filter media with an increase in filtration efficiency, as measured by E3 efficiencies using ASHRAE Test Standard 52.2. The components of a suitable chemical treatment may be selected from the group of one or more of a lubricant, an emulsifier, and an antistatic agent and are available from Goulston Technologies of Monroe, N.C.

(2) According to embodiments of the disclosure, the nonwoven filtration media is comprised of polymeric fibers selected from mono- and bi-component (bico) fibers. The bico fibers are composed of side-by-side fibers or sheath/core structure with polyethylene or polypropylene as the sheath polymer and polyethylene terephthalate (PET) as the core polymer. Bico fibers of this type are useful materials in the preparation of nonwoven webs for filtration media. The bico fibers can be readily obtained as staple fibers having sufficient crimp and spin finish to be processed in a carding operation. In general the lower melting polymer of the bico fibers allows thermal bonding to take place to add strength and integrity to the web. The bico fibers may also be combined with one or more fibers selection from polyethylene fibers, polypropylene fibers and polyester fibers.

(3) In one embodiment, the chemical treatment is used in a manner similar to a spin finish to the fibers before carding. The components of the chemical treatment may include, but is not limited to, an alkoxylated silicone copolymer and/or at least one antistatic agent. A suitable alkoxylated silicone copolymer may be selected from one or more of an ethoxylated silicone copolymer, a propoxylated silicone copolymer, and an ethoxylated/propoxylated silicone copolymer, and alkyl esters or sulfate modified sodium or calcium salts thereof. The antistatic agent may be selected from one or more of a cationic antistatic agent (cationic antistat), an anionic antistat (anionic antistat), or a quaternary antistatic agent (quat antistat). A weight ratio of alkoxylated silicone copolymer to antistat may range from about 4:1 to about 19:1, such as from about 17:3 to about 9:1. The total weight of chemical treatment applied to the fibers or fibrous material may range from about 0.05 to about 0.5 wt. %, such as from about 0.1 wt. % to about 0. 5 wt. % or from about 0.15 wt. % to about 0.45 wt. % of the total weight of the fibers or fibrous material

(4) The chemical treatment may be applied to the fibers by the fiber manufacturer in a traditional manner of producing staple fiber for carding. Application of the chemical treatment may be performed in the melt spinning operation and is usually accomplished by a kiss roll or metered flow applicator, where an aqueous emulsion of the chemical mix is applied per unit weight of the fiber. The chemical mix may also be applied in the secondary processes of drawing, crimping and cutting during production of the staple fibers.

(5) The addition of the chemical treatment is well controlled to allow sufficient processing of the staple bico fibers through the carding process. The add-on or weight percent finish is desirably in the range of from about 0.05 wt. % to about 0.5 wt. % of the total weight of the processed bico fibers. The amount of chemical treatment used is necessary to control the delicate balance of slip and stick necessary for fiber transfer within the moving rolls of the card, as well as the static level developed from the interactions of the fiber to moving metal parts during the carding process.

(6) Chemical treatment may also be applied to a fibrous nonwoven media. The fibrous nonwoven media may be formed using a variety of additional methods that include, but are not limited to, traditional dry laid and wet laid methods of forming nonwovens and continuous filament forming methods such as in a spunbond process. The application of the chemical treatment will depend somewhat on the nonwoven forming method; however tradition methods similar to those used in applying chemical treatments to synthetic fibers or woven webs, knitted and other textile-like materials, as well nonwovens materials may be used. Such methods include, but are not limited to, dipping, kiss coating, foaming, spraying and other finishing type operations known to those skilled in the art. Chemical treatment is effective on the surface of the fibrous nonwoven filter media.

(7) The fibrous nonwoven filter media composed of bico fibers is also capable of being scored, pleated or folded in order to form a pleated filter. The pleats of the filter can be formed by various conventional pleating operations that include, but are not limited to, bar, rotary, and star gear pleating operations.

(8) In one embodiment, the fibrous nonwoven filter media comprised of the bico fibers with the chemical treatment described above may be used to manufacture supported, self-supported or flat-sheet (not pleated) air or HVAC filters with at least a minimum efficiency rating (MERV) of MERV6 according to ASHRAE 52.2.

(9) The following examples are illustrative of exemplary embodiments of the disclosure. In these examples as well as elsewhere in this application, all parts and percentages are by weight unless otherwise indicated. It is intended that these examples are being presented for the purpose of illustration only and are not intended to limit the scope of the invention disclosed herein. Chemical formulation details giving the range of chemicals involved in the manufacturing of each of these chemical treatments in the following examples are shown in Table 1.

(10) TABLE-US-00001 TABLE 1 Chemical Treatment Chemical Formulation Details A Ethoxylated (1 mole to 300 moles)/Propoxylated (1 mole to 230 moles) C.sub.4 to C.sub.18 branched or linear alcohol B Ethoxylated (2 moles to 15 moles) C.sub.8 to C.sub.18 acid C (C.sub.4 to C.sub.18 branched or linear) alcohol phosphate neutralized (potassium or amine [monoethanol, diethanol, or triethanol]) D C.sub.8 to C.sub.18 amine ethoxylated (2 moles to 30 moles) sulfated quaternary (diethyl or dimethyl) E ethoxylated (1 mole to 300 moles)/propoxylated (1 mole to 230 moles) C.sub.4 to C.sub.18 branched or linear alcohol, C.sub.8 to C.sub.18 amine ethoxylated (2 moles to 30 moles) sulfated quaternary (diethyl or dimethyl), cyclic phosphate ester F silicone copolymer (1 to 300 repeating units) modified with ethoxylation (1 mole to 400 moles) and/or propoxylation (1 mole to 350 moles) acetate ester (0% to 100% capped), alcohols (C.sub.8 to C.sub.18 branched or linear) C.sub.2 to C.sub.6 diacid ester sulfate modified salt (sodium or calcium) G (C.sub.4 to C.sub.18 branched or linear) alcohol phosphate neutralized (potassium or amine [monoethanol, diethanol, or triethanol]), alcohols (C.sub.8 to C.sub.18 branched or linear) C.sub.2 to C.sub.6 diacid ester sulfate modified salt (sodium or calcium) H ethoxylated (2 moles to 40 moles) sorbitan esters, ethoxylated (2 moles to 50 moles) glyercides I Ethyl-N-hexadecylmorpholinium ethosulfate

EXAMPLE 1

(11) A fibrous nonwoven filter media at 90 grams per square yard (gsy) composed of 100 wt. %, 4-dpf bico fibers of PP/PET (sheath/core) identified in Table 2 as Sample 1, was formed using a carding process and bonded using thermal energy to provide strength to the nonwoven.

(12) The fibrous nonwoven filter media identified in Table 2 as Sample 1 was soaked in a hot water bath (120 deg F for a minimum of 3 min) then soaking was repeated at least 3 times, each time with fresh water to remove the water soluble finish applied by the fiber manufacturer. The media was allowed to dry overnight. The foregoing technique known as the Wash Method was used to produce chemical/finish free fibrous nonwoven filter media as a starting media for the application of other chemical treatments and is listed in Table 2 as Sample 2.

(13) In order to study the effect of other chemical treatments on the fibrous nonwoven filter media, numerous pieces of the nonwoven described above (Sample 1), were treated using the wash method to remove the finish supplied by the fiber producer to obtain a base nonwoven (Sample 2 in Table 2). Various chemical treatments noted in Table 2 were then applied to this base filter media nonwoven via an air brush spray unit and allowed to dry overnight. The chemically treated flat-sheets were then tested using ASHRAE 52.2 for their filtration efficiency performance.

(14) The spray technique of adding the chemical treatment was not critical as long as the amount of chemical add-on could be measured. The spray technique was used to mimic one method of chemical application used in commercial processing. The add-on is determined by a weight difference in the media before and after spraying.

(15) TABLE-US-00002 TABLE 2 % Improvement Sample Wt % Add- E3 in E3 Number Chemical Treatment On Efficiency (over base) 1 PP/PET-nonwoven 0.3 69 35.3 produced with unknown spin finish supplied by fiber manufacturer 2 (sample 1 above 0 51 Base with spin finish removed via wash method) Base media at 90 gsy 3 A 0.2 58 13.7 4 B 0.2 59 15.7 5 C 0.1 60 17.6 6 D 0.1 65 27.5 7 E 0.3 64 25.5 8 F 0.4 75 47.1

(16) As shown in Table 2, a fibrous nonwoven flat-sheet prepared from Sample 1 media had an E3 efficiency rating of 69. The E3 value indicated that the filter media met at least a MERV6 filtration efficiency, where 3.0-10.0 micron particles are removed at greater than or equal to 35% to less than 70%.

(17) The finish free (washed) media identified in Table 2 as sample 2 was tested using ASHRAE 52.2. The E3 efficiency rating dropped to 51 as compared to the unwashed sample of 69 noting that the spin finish applied by the fiber manufacturer had some beneficial effect on filtration efficiency.

(18) Samples 3 and 4 had chemical treatments A & B applied respectively using a spray technique. The chemical treatments were applied individually to the base nonwoven at 0.2 wt. % add-on. The E3 efficiency rating of Samples 3 and 4 according to the ASHRAE 52.2 test were 58 and 59 respectively. Accordingly, changing the viscosity of the treatment made little difference in the E3 efficiency rating of the media.

(19) As shown in Table 2, a chemical treatment C was sprayed onto the base nonwoven at a 0.1 wt. % add-on to provide Sample 5. Sample 5 had an E3 efficiency ratio of 60. Treatment C is an example of anionic antistat.

(20) Sample 6 in Table 2 was prepared by spraying 0.1 wt. % of treatment D a Quat antistat onto the base. This wt. % add-on resulted in an efficiency of 65 when tested using ASHRAE 52.2.

(21) Since chemical spin finishes typically include a complex mixture of several components such as a lubricant, an antistatic agent and an emulsifier, it was important to understand the effect of the combination of these materials on filtration efficiency. Sample 7 (Table 2) comprises chemical treatment E a lubricant combined with an antistat that was applied as a spray to the base media (90 gsy) at a level of 0.3 wt. %. The E3 efficiency rating of Sample 7 was 64 from the ASHRAE 52.2 testing.

(22) Sample 8 (Table 2) utilizes a chemical treatment F at 0.4 wt. % add-on. The nonwoven media of Sample 9 had an E3 efficiency rating of 75 which was a 47% increase in E3 rating over the base nonwoven media (Sample 2).

EXAMPLE 2

(23) A second nonwoven media for testing was made by carding 100 wt. %, 2-dpf bicomponent fibers of PE/PET to produce a 52 gsy nonwoven media. The wash method, described above, was used on the media to remove the chemical finish applied by the fiber manufacturer to create a new base media as Sample 9 in Table 3. All of the samples in Table 3 including the base media of Sample 9 and the indicated treatments were tested according to ASHRAE 52.5.

(24) TABLE-US-00003 TABLE 3 % Improvement Sample Wt % E3 in E3 (over Number Chemical Treatment Add-On Efficiency base) 9 Base media 52 gsy 0 75 Not Applicable 10 F 0.3 94 25.3 11 (90/10) wt. ratio F/D 0.3 94 25.3 12 H 0.3 92 22.7 13 (85/15) wt. ratio F/C 0.3 96 28.0

(25) As shown in Table 3, Sample 9, the base media had an E3 efficiency rating of 75.

(26) Sample 10 (Table 3) was the base media of Sample 9 that was treated with 0.3 wt. % of chemical treatment F using a spray application method. Sample 10 had an E3 efficiency rating of 94 which was a 25.3% increase in E3 efficiency over the base (Sample 9).

(27) The base media was treated with a chemical formulation that included 90 wt. % chemical treatment F/10 wt. % chemical treatment D to produce Sample 11. The formulation was applied at a 0.3 wt. % add-on via the spray method. Sample 11 had an E3 efficiency rating of 94 which was comparable to the E3 rating of Sample 10. Thus the antistat (Chemical treatment D) provided little or no additional improvement in the E3 efficiency rating of the media.

(28) Sample 12 (Table 3) was the base media with chemical treatment H that was applied to the media at an add-on of 0.3 wt. % via the air spray method. Sample 12 had an E3 efficiency rating of 92 when tested using ASHRAE 52.2. The E3 rating of Sample 12 compared favorably to the E3 rating of Samples 10 an 11.

(29) Sample 13 was the base media treated with 85/15 weight ratio of chemical treatments F/C to provide a 0.3 wt. % add-on. Sample 13 had an E3 efficiency rating of 96.

EXAMPLE 3

(30) A third nonwoven web was produced by carding followed by thermal bonding to give a web that measured at 78 gsy. The fibers used were a 2-dpf bicomponent of PE/PET. After several hot water rinses to remove the spin finish applied by the fiber supplier (Wash Method) followed by a 24 hours air drying, the sample was tested using ASHRAE 52.2 to give an E3 efficiency rating of the base media of 72 (Sample 14). Table 4, shows examples of increasing the concentration of various chemical treatments and their effect on the E3 efficiency rating of the media after testing according to ASHRAE 52.2.

(31) TABLE-US-00004 TABLE 4 Wt % Add-On (based % Improvement upon E3 in E3 Sample Chemical Treatment actives) Efficiency (over base) 14 Base 78 gsy 0 72 Not Applicable 15 (90/10) wt. ratio F/D 0.15 87 20.3 16 (90/10) wt. ratio F/D 0.3 90 25.0 17 (90/10) wt. ratio F/D 0.45 93 29.2 18 H 0.15 82 13.9 19 H 0.3 84 16.7 20 H 0.45 86 19.4 21 (85/15) wt. ratio F/C 0.15 88 22.2 22 (85/15) wt. ratio F/C 0.3 89 23.6 23 (85/15) wt. ratio F/C 0.45 91 26.4

(32) Samples 15, 16 and 17 showed that increasing add-on amounts (0.15 wt. % to 0.3 wt. %) applied via air spraying to the base Sample 14, a 90/10 weight ratio of chemical treatments F/D, increased the E3 efficiency ratings from 87 to 90 to 93 respectively.

(33) Samples 18, 19 and 20 were base samples treated with chemical treatment H with increasing add-on concentrations (0.15 wt. % to 0.3 wt. % to 0.45 wt. %). The E3 efficiency ratings of Samples 18, 19 and 20 were 82, 84 and 86 respectively when tested using ASHRAE 52.2. These efficiency ratings are lower than those obtained from the 90/10 wt ratio of treatments F/D, (Samples 15-17, Table 4).

(34) Samples 21, 22 and 23 were base samples treated with increasing amount (0.15 to 0.45 wt. %) of a 90/10 weight ratio of chemical treatments F/C. Samples 21, 22 and 23 showed a similar increase in E3 efficiency ratings with increasing amounts of treatment when tested using ASHRAE 52.2. The samples in Table 4 showed that the chemical formulation concentration also had an effect on the E3 efficiency rating values.

(35) Accordingly, the chemical formulations in each of the above examples may be used as a spin finish that also functions as a process aid in carding. Optimum application (add-on) during fiber spinning is typically based upon optimum run-ability during carding. The formulation typically must have sufficient lubrication to aid in reducing fiber-to-metal friction, add cohesion to assist in fiber-to-fiber cohesion and eliminate static.

EXAMPLE 5

(36) The Samples of Table 5 also provided examples of using certain chemicals as a fiber finish where a bicomponent staple fiber producer applied the chemical treatment to a 5-dpf PE/PET bicomponent fiber at a level of 0.3 wt. % add on. Sample 24 was the base nonwoven at 105 gsy that has been stripped of finish using the wash method described above.

(37) TABLE-US-00005 TABLE 5 Wt % Add- % On (based Improvement Sample upon E3 in E3 Number Chemical Treatment actives) Efficiency (over base) 24 Base 105 gsy 0 70 Not Applicable 25 (90/10) wt. ratio F/I 0.3 89 36.9 26 (85/15) wt. ratio F/G 0.3 90 38.5

(38) Sample 25 was a 106 gsy nonwoven produced from a carded process that was thermally bonded using the 5-dpf PE/PET staple fibers containing 0.3 wt. % of a chemical treatment that included 90 wt. %/10 wt. % of chemical treatments F/I. The nonwoven media of Sample 25 was tested according to ASHRAE 52.2 and provided an E3 efficiency rating value of 89. Good processing was noted in carding Sample 25 fiber. No problems were noted with static build-up, cohesion or fiber feeding or clumping.

(39) A 104 gsy nonwoven media (Sample 26) was produced by carding followed by thermal bonding of a 5-dpf PE/PET bicomponent fiber containing a chemical formulation at 0.3 wt. % add-on supplied by Goulston Technologies, Inc. The chemical formulation listed for Sample 26 in Table 5 included 85 wt. %/15 wt. % of chemical treatments F/G. The chemical formulation was added to the PE/PET bico fibers during the staple fiber manufacturing process. Sample 26 had an E3 efficiency rating of 90 when tested according to ASHRAE 52.2.

(40) One will note that the E3 efficiencies of Samples 25 and 26 in Table 5 were very high for essentially the same nonwoven media. The chemical treatments of Samples 25 and 26 also provided no processing problems during the carding process; noting no static, good lubrication and good fiber cohesion at carding line speeds greater than 120 feet per minute.

(41) It is noted that, as used in this specification and the appended claims, the singular forms a, an, and the, include plural referents unless expressly and unequivocally limited to one referent. Thus, for example, reference to an antioxidant includes two or more different antioxidants. As used herein, the term include and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items

(42) For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

(43) While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or can be presently unforeseen can arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they can be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.