CN108770347B

CN108770347B - Layered filter assembly for closure protection

Info

Publication number: CN108770347B
Application number: CN201780003244.7A
Authority: CN
Inventors: R·吉杜马尔; 尹江文; 刘晓熹; 宁宏; 王攀
Original assignee: WL Gore & Associates (shenzhen) Inc; WL Gore and Associates Inc
Current assignee: Z Heitian (Thailand) Ltd.
Priority date: 2017-02-22
Filing date: 2017-02-22
Publication date: 2021-09-28
Anticipated expiration: 2037-02-22
Also published as: CN108770347A; WO2018152683A1

Abstract

The layered filter assembly may include a filtration layer and one or more porous support layers adjacent to the filtration layer. The filter layer may be formed of polyester having a non-uniform fiber size of 0.1 microns to 10 microns.

Description

Layered filter assembly for closure protection

Technical Field

The present disclosure relates generally to a filter assembly for capturing particulate and/or vapor contaminants, and a method of mitigating contamination of an electronic device enclosure.

Background

Filtration technology is used in many applications and environments for protecting sensitive components of electronic devices, such as Hard Disk Drives (HDDs), from particulate and/or vapor contaminants in the electronics enclosure.

Many closures that include sensitive equipment must maintain a very clean environment for the equipment to function properly. Examples include the following closures: optical surfaces or electronic components that are sensitive to particles and gaseous contaminants that can interfere with mechanical, optical, or electronic operation; data recording devices, such as computer hard disk drives that are sensitive to particulates, organic vapors, and corrosive vapors; processing and storage of thin films and semiconductor wafers; and electronic controllers such as those used in automotive and industrial applications that are sensitive to particle, moisture accumulation and corrosion, as well as liquid and vapor contaminants. Contamination in the closure originates from both the interior and exterior of the closure. For example, the HDD may be damaged due to external contaminants entering and/or being recirculated within the enclosure of the HDD. Contaminants may also include particles and vapors generated inside the HDD enclosure.

Known filters are disclosed, for example, in U.S. patent No. 7,306,659 ("the' 659 patent"), which is incorporated herein by reference for all purposes. The' 659 patent discloses a device for filtering contaminants, such as particulate and vapor phase contaminants, from an enclosed environment, such as electronic or optical devices susceptible to contamination (e.g., computer disk drives), by improving performance and potentially incorporating multiple filtering functions into a monolithic filter. The filter includes a flow layer that improves the performance of the filter. The filtration function includes a passive adsorption component and may include a combination of an inlet, a breather filter, and an adsorbent filter. In addition, recirculation filters, diffuser pipes and externally mounted functions may be added to the filter depending on the function desired within the closure.

Typical adsorbents and recirculation filters require a large volume to be effective. However, space-saving assemblies are described in some of the following references. U.S. patent No. 6,266,208 describes a monolithic filter incorporating a recirculation filter, a breather filter and an adsorbent filter. U.S. patent No. 6,238,467 describes a rigid assembly filter incorporating a breather filter, an adsorbent filter and a recirculation filter. U.S. patent No. 6,296,691 describes a molded filter incorporating a breather filter and a recirculation filter. U.S. patent No. 6,395,073 describes the incorporation of a recirculation filter, and a breather filter with an optional sorbent filter into an unobtrusive profile (low profile) adhesive construction.

Conventional designs use polypropylene electret felt as at least one filter material in the recirculation filter of the disk drive. However, it was found that polypropylene fibers from the electret felt create a risk of Head Disk Interface (HDI) damage, resulting in reduced HDD reliability. Furthermore, as disk drives decrease in size, solutions are sought that occupy less volume. Accordingly, there is a need for non-polypropylene filtration techniques for protecting sensitive components of electronic devices that can operate with an unobtrusive profile in a small enclosure without sacrificing airflow or sorption performance.

Disclosure of Invention

According to one embodiment of the present disclosure, a layered filter assembly is provided that includes a filtration layer and one or more porous support layers adjacent to the filtration layer. The porous support layer may be positioned along one side of the filter layer or along both sides of the filter layer; and may be configured to provide support to the filter layer without significantly increasing the air resistance of the layered filter assembly. In some embodiments, the porous support layer is in contact with the filtration layer without any intermediate layer. The assembly may have a filtration efficiency of 65% or more, and a thickness of about 100 to 250 μm.

In accordance with another embodiment, a layered filter assembly is provided that includes a filter layer, one or more porous support layers, an adsorbent layer, and a media layer, wherein the adsorbent layer is positioned between the filter layer and the media layer. One or more porous support layers are adjacent to and external to the filtration layer and/or the media layer.

According to other embodiments, an article for filtering a closure is provided that includes a housing for holding an electronic device, a layered assembly disposed within the housing, and a filter layer comprising a polyester layer. The layered filter assembly includes a filtration layer and one or more porous support layers adjacent to the filtration layer.

In each of these embodiments, the filtration layer may be formed from polyester having a non-uniform fiber size of 0.1 microns to 10 microns. According to one embodiment, the filter layer may be a meltblown polyester that is substantially free of polypropylene. For the purposes of this disclosure, substantially free means that the component is present in a limited amount of less than 0.1 weight percent, and includes complete absence of the component.

Brief description of the drawings

The invention will be better understood with reference to the attached non-limiting drawings.

FIG. 1 is a cross-sectional side view of an embodiment of a layered filter assembly.

Fig. 2 is a cross-sectional side view of a second embodiment of a layered filter assembly.

Figure 3 is a cross-sectional side view of a third embodiment of a layered filter assembly.

Fig. 4 is a Scanning Electron Microscope (SEM) photograph showing a filter material having substantially uniform fibers.

Fig. 5 is an SEM image showing a filter material having a non-uniform fiber size according to embodiments described herein.

Fig. 6 is a cross-sectional side view of an electronic device assembly according to embodiments described herein, showing the layered filter assembly of fig. 1-3 installed therein.

FIG. 7 is a cross-sectional side view of a filtration efficiency testing assembly and system.

Fig. 8 is a graph illustrating the filtration efficiency of various test samples.

Detailed Description

Various embodiments described herein provide a layered filter assembly comprising a filtration layer and one or more porous support layers adjacent to the filtration layer. In one embodiment, the filter layer comprises polyester containing non-uniform fiber size fibers of 0.1 microns to 10 microns. In one embodiment, the filter layer may also be substantially free of polypropylene. The weighing filter assembly is suitable for use, for example, in an electronics enclosure. The layered filter assembly can be used to filter air therein without taking up excessive space, without significantly impeding airflow, without shedding fibers into the closure elements, and without the disadvantages associated with conventional (e.g., polypropylene) filter layers.

Other embodiments include a sorbent layer and a media layer, wherein the sorbent layer is disposed between the filter layer and the media layer. In one embodiment, the media layer is a non-polypropylene layer having a greater air permeability than the filter layer. The dielectric layer may be a non-woven polyester thermoplastic such as polyethylene terephthalate. In some other embodiments, the dielectric layer may be polyethylene, polyvinyl alcohol, a mixture of the above, or the like. The sorbent layer can be positioned between the filter layer and the media layer, and the porous support layer is positioned adjacent to opposing surfaces of the media layer and the filter layer. The sorbent layer can include any suitable sorbent material, such as, but not limited to, activated carbon, or a porous substrate containing activated carbon. In some embodiments, the sorbent layer can comprise ePTFE and a sorbent material. Other suitable adsorbent materials may include, but are not limited to: a suspension of sodium carbonate, calcium sulfate, potassium carbonate, any suitable mixture of the foregoing, or any suitable combination of the foregoing in a base material. In alternative embodiments, the media layer may have similar properties to the filter layer, such that the sorbent layer may be located substantially between two layers having similar properties.

The present disclosure may be better understood with reference to the following drawings, wherein like parts are given like numerals throughout

Conventional filter assemblies, including those used in recirculation filtration and the like, are typically made using filter media composed of polypropylene fibers that are electrostatically charged by a carding process. The resulting material, which is a polypropylene electret felt, is capable of mechanically capturing contaminants and also exerting electrostatic forces on the particles to increase the cleaning capacity of the filter media. However, polypropylene fibers exhibit a number of disadvantages. For example, polypropylene fibers released by electret felt can threaten sensitive electronics, such as Head Disk Interface (HDI) of a Hard Disk Drive (HDD), causing reliability degradation of the HDD. In this regard, there is an increasing demand for polypropylene-free filters with adequate particulate removal performance. Fig. 4 is a Scanning Electron Microscope (SEM) photograph showing a filter material 400 having substantially uniform fibers 402 in a conventional polypropylene electret mat material.

For comparison, fig. 5 is an SEM image showing a polyester filter material 500 having a non-uniform fiber size according to some embodiments of the present disclosure.

Referring to FIG. 1, a cross-sectional side view of an embodiment of a layered filter assembly 100 is shown. Layered filter assembly 100 includes a filtration layer 102 and two

porous support layers

104a, 104b adjacent to and on either side of the filtration layer. Filtration layer 102 is a polyester layer having fibers of non-uniform fiber size, wherein the fiber size ranges from 0.1 μm to 10 μm. It is understood that fiber size is determined by cross-sectional diameter. By non-uniform fiber size is meant that the fibers in the polyester layer have different cross-sectional dimensions that produce a distribution of fiber sizes. It should be understood that while the non-uniform fiber size may range from 0.1 μm to 10 μm, there may be some smaller or larger individual fibers. The fiber size distribution may vary, such that, for example, in one embodiment, the first portion of the fibers ranges from 0.1 μm to 3.0 μm, and the second portion of the fibers ranges from 3.0 μm to 10 μm. The first portion may be 10% to 90% of the total fibers and the second portion may be 90% to 10% of the total fibers in an embodiment, 85% of the fibers have a fiber size in the range of 0.1 μm to 3.0 μm and 15% of the fibers have a fiber size in the range of 3.0 μm to 5.0 μm. In other embodiments, the fiber sizes may have a bimodal distribution, with a first average fiber size ranging from 0.1 μm to 3.0 μm and a second average fiber size ranging from 3.0 μm to 5.0 μm. The first average fiber size range may include about 85% fibers and the second average fiber size range may include about 15% fibers. In other embodiments, the fiber size distribution may be multimodal.

As discussed herein, the filter layer 102 is a meltblown polyester polymer. In some embodiments, filter layer 102 is meltblown polybutylene terephthalate. Filter layer 102 is substantially free of polypropylene. In some alternative embodiments, filtration layer 102 may comprise an electrospun non-polypropylene polymeric nonwoven, or a multicomponent spun non-polypropylene polymeric nonwoven.

Suitable filter layers have adequate flow and resistance properties while being thin and lightweight. According to some embodiments, the gas permeability of the filter layer 102 at 125Pa is at least 15.24 cubic meters of air per minute square meter (meters per minute), or 50 cubic inches of air per minute square feet (cfm/ft)²). In some embodiments, the gas permeability of the filter layer 102 at 125Pa ranges from 15.24 meters per minute to 30.5 meters per minute (i.e., 50 to 100 cfm/ft)²). According to some exemplary embodiments, filter layer 102 may have an air resistance of less than 20 Pa. Furthermore, the filter layer may be lightweight and can be made thin for small closures. In one embodiment, the thickness 110 of the filter layer 102 is less than 250 μm, such as less than 200 μm. In some ranges, suitable filter layers have a thickness in the range of 100 μm or 250 μm. The weight of the filter layer may range from 15g/m²To 50g/m²For example, 22g/m²To 40g/m²。

The filter layer also has sufficient collection efficiency over a wide range of particle sizes (e.g., 0.05 μm to 10 microns).

Two

porous support layers

104a, 104b are shown, but it is understood that in some embodiments, one of the two porous support layers may be omitted. The one or more porous support layers 104a, b preferably have a porosity that is significantly higher than the filtration layer 102 so that the porous support layers do not significantly affect the gas permeability of the filtration layer or the airflow through the filtration layer. The one or more porous support layers 104a, b may be composed of any suitable support material, such as a woven scrim having a high gas permeability as compared to the filtration layer 102. One or more of the porous support layers 104a, b may be composed ofPolypropylene material, such as polyester woven. In some alternative embodiments, one or more of the porous support layers 104a, b may be composed of, for example, polyethylene, polyvinyl alcohol, mixtures thereof, or the like. Preferably, the one or more porous support layers have an air permeability of at least 152 cubic meters of air per square meter (500 cfm/ft) at 125Pa²). The thickness 112a, b of the porous support layers 104a, b may be about 100 μm to 400 μm.

In some embodiments, the layered filter assembly 100 may be assembled by: porous support layers 104a, b are laid across filtration layer 102 to support the filtration layer and/or to prevent the filtration layer from releasing fibers. This means that the

distance

120, 122 between the filter layer 102 and the porous support layers 104a, b can be very small, i.e., about 0 microns. The filter layer 102 and porous support layers 104a, b may be joined at one or more sides or edges, such as by mechanical means (including clamps, potting, or any suitable mechanical fasteners); by joining or laminating along one or more sides or edges of the assembly, or by adhesive joining the layers. In some embodiments, filter layer 102 may comprise a layer of hot melt adhesive on one or more surfaces (not shown) capable of adhering to one or more adjacent porous support layers 104a, b.

The layered filter assembly 100 is operable to filter an air stream flowing therethrough by removing a substantial amount of entrained small particles. An exemplary embodiment of the layered filter assembly 100 was tested on a TSI-8130 automated filtration tester (TSI corporation) with 0.3 μm NaCl particles at a flow rate of 5.3 cm/sec, as described in more detail below with reference to table 1. Exemplary embodiments of the layered filter assembly achieve a filtration efficiency of at least 65% at a 32 Liter Per Minute (LPM) flow rate. According to an embodiment, the layered filter assembly 100 may also achieve a filtration efficiency of 80% or greater. The layered filter assembly 100 has a total airflow resistance of less than 30Pa, for example, less than 20 Pa; or in the range of 10Pa to 30Pa, for example 15Pa to 20 Pa.

According to some embodiments, the layered filter assembly may further include one or more adhesive elements or layers located on the exterior of one or more of the filter support layers 104a, b, e.g., for bonding to a housing or other device housing the layered filter assembly. The layered filter assembly may further include a damping material for reducing vibrations within the housing. Also, as described in the present disclosure, the layered filter assembly may include additional layers, such as a sorbent layer, a media layer, and/or a second filter layer. Examples of layered filter assemblies with additional layers are described below with reference to fig. 2 and 3.

Fig. 2 is a cross-sectional side view of a second embodiment of a layered filter assembly 200. The second layered filter assembly 200 comprises: a filter layer 202, and a media layer 208 and a sorbent layer 206 on the sorbent layer opposite the filter layer. The combination of the filter layer 202, the sorbent layer 206, and the media layer 208 can be connected by adjacent

porous support layers

204a, 204 b. According to various embodiments, the filter layer 202 and porous support layers 204a, b may have similar structures and characteristics as the filter layer 102 and porous support layers 104a, b described above in fig. 1.

The sorbent layer 206 can comprise any suitable porous support layer for the sorbent, such as, but not limited to, activated carbon, or a porous substrate containing activated carbon. For example, one suitable adsorbent porous support layer may comprise a plurality of activated carbon beads or particles within two scrim racks. The sorbent layers are preferably operable to adsorb vapor contaminants, such as organic vapors, from an air stream flowing through the layered filter assembly 200.

The media layer 208 disposed adjacent to the sorbent layer 206 and opposite the filter layer 202 is operable to prevent particles from dispersing from the sorbent layer 206, but is generally more porous than the filter layer 202, i.e., has a lower air resistance than the filter layer. The air resistance of the medium layer may be lower than that of the filter layer, and may be lower than 3 Pa. The thickness of the dielectric layer may range from 0.5 to 1.3mm, for example, from 1.0 to 1.3 mm. Suitable materials for the dielectric layer may include: for example, nonwovens, particularly nonwoven polyesters formed by carding, spunbonding, or meltblowing processes. In one embodiment, the dielectric layer is a polyester meltblown, for example, a polyethylene terephthalate nonwoven.

In a similar manner to the layered filter assembly 100 described in fig. 1, the layers comprising the layered filter assembly 200 may be separated by

distances

200, 222, 224, 226. Some or all of the separation distances may be 0 or approximately 0. For example, the layers may be assembled by mechanically fastening the layers into the layered filter assembly 200 along the edges or separation points of the filter assembly. In other embodiments, the layers may be bonded to each other at discrete points at the edges or along adjacent surfaces. In other embodiments, the layers may be continuously bonded to each other along the adjacent surfaces. In some embodiments, the filter layer 202 and/or the media layer 208 may comprise a layer of hot melt adhesive on one or more surfaces (not shown) capable of adhering to one or more adjacent

porous support layers

204a, 204 b. Alternatively or in combination, the filter layer 202 and/or the media layer 208 can be bonded to the sorbent layer 206 by a layer of a melt adhesive or the like.

Fig. 3 is a cross-sectional side view of a third embodiment of a layered filter assembly 300. The third layered filter assembly 300 includes a first filter layer 302a and a second filter layer 302b, the second filter layer 302b being positioned similarly to the media layer 208 of the exemplary assembly 200 shown in fig. 2. The second filter layer 302b may also be a dielectric layer and perform the same function as the dielectric layer 208 described above in fig. 2.

Also, in a similar manner as the

layered filter assemblies

100 and 200 described above, the layers comprising the layered filter assembly 300 may be separated by

distances

300, 320, 324, 326. In some embodiments, the separation distance may be 0 or approximately 0, and the layers may be attached together by one or more of the methods discussed above with respect to layered

filter assemblies

100 and 200.

Referring now to FIG. 5, an exemplary large fiber 502 exhibits an approximate diameter range of 3 μm to 5 μm in a nonwoven arrangement of small fibers 504 having an approximate diameter of 0.1 μm to 3 μm. In some embodiments, filter layer 500 is a meltblown polyester. Specific polyesters include: for example, polybutylene terephthalate, but other polyester meltblown materials are also within the scope of the present disclosure. The fiber size distribution of the meltblown polyester changes. According to some embodiments, suitable fiber size distributions include: a first fiber size range of 0.1 μm to 3.0 μm constituting up to 85% of the fibers, and a second size range of 3.0 μm to 5.0 μm constituting up to 15% of the fibers. Polyester meltblown materials (e.g., the filter material 500 described above) may be formed by a one-step process in which high velocity air blows molten thermoplastic resin onto a conveyor belt. Suitable processes for producing polyester meltblown materials are discussed in, for example, Dutton, K.C. (2008) "summary and analysis of meltblown processes and parameters (" Overview and analysis of the meltblow process and parameters) ", Journal of Textile and apparatus, Technology and management.6; and McCulloch, J.G. (1999) "The history of meltblown technology development", International nowwindows journal.8, which is incorporated herein by reference.

The fiber size range in the polyester filter material 500 is operable to capture particles more effectively than filter materials having uniform fiber sizes, particularly for very small particles. However, this improvement in electret felt (electret felt) for polyester filter material was unexpected based only on the raw material properties of comparable filter materials. Sample raw material properties of exemplary polypropylene 400 and polyester meltblown 500 filter materials are shown in table 1 below.

Table 1: raw material Properties of electret felt and polyester melt blown Filter materials

Table 1 shows the material properties of the electret felt and polyester melt blown filter materials as described above, as well as the air quality and efficiency measurements obtained on a TSI-8130 automatic filtration tester (TSI Corp.) with 0.3 μm NaCl particles at a flow rate of 5.3 cm/sec. A polyethylene terephthalate dielectric layer is also shown for comparison purposes, similar to the dielectric layer 208 described above in fig. 2.

The polyester meltblown material had a thickness in the range of 102-254 μm (about 4-10 mils) and a basis weight in the range of 22-40 g/m²(Table 1). The material is charged to enhance particle capture. Filtration of meltblown as a function of electro-and mechanical filtrationThe efficiency was determined to be 80-90% and the penetration was done with 0.3 μm NaCl particles at a rate of 5.3 cm/sec. At the same time, the resistance to air flow recorded in the same test is between 14.7 and 19.6Pa (about 1.5-2.0mm H)₂O). Polyester meltblown material is 65% lighter and 85% thinner than electret felt traditionally used in recirculation filters. Thus, the overall thickness of the recirculation filter may be reduced by up to 50%, and the overall thickness of the sorbent recirculation filter may be reduced by 30%. Meltblown materials have the same filtration efficiency but have much higher air flow resistance, for example 5 times greater than electret felt. Based solely on raw material properties, polyester meltblown is generally expected to have poorer filtration performance than electret felt, especially in recirculation filtration, because polyester meltblown has significantly reduced air permeability. However, as described in this disclosure, polyester meltblown materials having non-uniform fiber sizes and being substantially free of polypropylene achieve equivalent or improved particle removal performance. Without being bound by theory, meltblown materials have finer fiber sizes and a wider fiber size distribution, which is more attractive for various particle sizes traveling at various speeds.

Fig. 6 is a cross-sectional side view of an electronic device assembly 600 showing the layered filter assembly 608 of each of fig. 1-3 installed therein, according to embodiments described herein. The particular device shown is a Hard Disk Drive (HDD) in which the layered filter assembly 608 is employed as a recirculation filter in the electronics housing 602. In operation, the internal components 604 of the electronics assembly 600, which may include a Head Disk Interface (HDI), may generate particles and/or vapors while causing an amount of recirculation 610 within the interior 606 of the housing 602. In the recycle stream 610, particles and/or vapors are trapped by the layered filter assembly 608.

Specific performance of the layered filter assembly may be obtained by simulating the end use environment, for example, by a continuous particle introduction test method.

Test method

FIG. 7 is a cross-sectional side view of a filtration test assembly and system 700 according to some embodiments. Test system 700 may be configured to obtain particle removal Performance (PCU) and/or vapor removal performance (VCU) for exemplary recycled particles.

The testing system 700 includes a mass flow controller 702, testing equipment 704 including an electronics enclosure 720, and an analyzer 706 under the control of a management component 708 (e.g., a computer controller), the management component 708 employing a processor 714 and a non-transitory memory 716 storing instructions to control characteristics of respective tests. The testing system 700 is operable to pass a test contaminant (e.g., particles, vapor) through the valve 712 and into the injection port 724 of the closure 720 and periodically sample the air within the closure via the sample port 726.

Particle removal (PCU) test

Under the control of the management assembly 708, the mass flow controller 702 may introduce a particle-laden air stream into the electronics enclosure 720 through the injection port 714. The particle laden air will circulate throughout the closure 720, which will interact with the layered filter assembly 722.

Air is sampled from the closure member through sample port 726 to obtain a concentration difference between the unfiltered air particulate content and the filtered air particulate content. The particles used were polystyrene latex spheres (PSL) supplied by the company semer hewler science (Thermo Scientific Inc.) suspended in water and then atomized using a 3076Aerosol Generator (3076Aerosol Generator) from the company TSI. The aerosol stream is then dried using a diffusion dryer and drawn into the closure member 720 through the injection port 724 at a constant flow rate. The particle counter used for this test was a laser aerosol spectrometer 3340 from TSI corporation. The result of the particle removal test is recorded as T90, which is defined as the time required to remove 90% of the particles in the drive. The second result is the Relative Clearance (RCUR), recorded as T90 recorded with the filter versus T90 recorded without the filter. The smaller the T90 and RCUR, the better the particle removal performance. The PCU test results for electret felt (comparative) and polyester melt blown (invention) samples of a recirculation filter similar to that shown in fig. 1 (i.e., a recirculation filter without an adsorbent) are shown in table 2 below.

Table 2: PCU test results for recirculation filter

As shown in Table 2 above, the T90 and RCUR values for the polyester melt blown example of the present invention and the comparative example of electret felt for a recirculation filter are comparable, indicating that the particle retention performance of the filter assembly according to the embodiments described herein is similar to that of a conventional electret felt filter. Indeed, despite the significantly thinner polyester melt blown layered filter assembly, the polyester melt blown layered filter assembly outperformed the conventional electret felt filter and the T90 time was on average 2 seconds faster than the conventional filter and the RCUR ratio increased by 6% to 7%.

Particulate removal data for an adsorbent recirculation filter configured in a similar manner as the adsorbent recirculation filter of fig. 2 was also obtained using the same method as discussed above. These PCU results are shown in table 3 below.

Table 3: PCU test results for adsorbent recirculation filters

As shown in Table 3, the T90 data for the meltblown examples of the present invention was found to be 13 seconds, while the T90 for the conventional electret felt was found to be 10 to 11 seconds. The RCUR data showed less than 10% difference between the two filters. Although judged only from raw material properties, it appears that meltblown materials are a poor filter material compared to electret felt in recirculation filtration; these data indicate that the use of meltblown materials results in substantially equivalent particle removal performance. Vapor purge (VCU) test

Organic vapor breakthrough times can be measured by passing an air stream containing a predetermined concentration of a volatile organic standard through an adsorbent vent assembly. The concentration of the volatile organic standard may be measured in the air stream exiting the sorbent aeration assembly. A common volatile organic standard used in this test is Trimethylpentane (TMP). Although the test results herein are disclosed in terms of TMP breakthrough, the breakthrough times will be comparable to similar organic vapors.

In VCU testing, mass flow controller 702 may optionally introduce a stream of air containing vapor into electronics enclosure 720 through injection port 714 under the control of management assembly 708. Air containing vapor will circulate throughout the enclosure 720, which interacts with a layered filter assembly 722 (similar to

layered filter assemblies

200, 300 shown in fig. 2 and 3) that includes a sorbent layer.

In each VCU test, the layered filter assembly tested was located in the same type of closure member 720 as described above for the PCU test. An air flow of 30 ml/min with 120ppm Trimethylpentane (TMP) is injected into the closure through an injection port 724 in the cap of the closure 720. The air sample is drawn from the drive through sampling port 726. A gas chromatograph (Agilent Technologies Inc.) gas chromatograph 7820A, along with a data acquisition system, is connected to sampling port 726 and is used to obtain an outlet TMP concentration over time. The vapor removal efficiency was determined as the TMP breakthrough concentration at 3 hours, i.e. the ratio of the outlet TMP concentration to the inlet TMP concentration. The lower the breakthrough concentration, the higher the vapor removal efficiency.

FIG. 8 is a graph illustrating the filtration efficiency of an electret felt filter assembly (comparative example 804) and a polyester melt blown layered filter assembly of the present invention (example 1,802). The graph shows that the filter assemblies of both examples have near 10% VCU efficiency (about 9.7% at 3 hours for comparative example, about 11.7% for example 1). Thus, VCU testing demonstrated that while layered filter assemblies using polyester melt blown filter layers were significantly thinner, layered filter assemblies using polyester melt blown filter layers could achieve VCU efficiencies comparable to conventional electret felt-based filter assemblies. The invention has now been described in detail for purposes of clarity and understanding. However, one of ordinary skill in the art appreciates that certain changes and modifications can be made that are within the scope of the appended claims.

In the previous descriptions, for purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present invention. It will be apparent, however, to one skilled in the art that certain embodiments may be practiced without some of these specific details, or with additional details.

Although a few embodiments have been described, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be made without departing from the spirit of the embodiments. In addition, many known methods and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention or the claims.

Where a range of values is provided, each intervening value, to the minimum fraction in the unit of the lower limit between the upper and lower limit of that range, is also to be considered specifically disclosed, unless the context clearly dictates otherwise. Any narrower range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The stated ranges may independently include or exclude the upper and lower limits of these smaller ranges, and the invention also includes ranges where these smaller ranges do not include a limit, include either or both limits, subject to the explicit exclusion of any limit from the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those limits are also included.

As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Also, the words "comprise," "comprising," "include," "including," "contains," "having," "has," "having" and "containing," when used in this specification and the appended claims, are intended to specify the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof.

In the following, further embodiments are described to facilitate understanding of the present disclosure:

E1. a layered filter assembly comprising: a filtration layer comprising polyester comprising fibers having a non-uniform fiber size of 0.1 μ ι η to 10 μ ι η; and one or more porous support layers adjacent to the filtration layer.

E2. A layered filter assembly as set forth in any preceding embodiment wherein the non-uniform fiber size ranges from 0.1 μm to 5 μm.

E3. A layered filter assembly as set forth in any preceding embodiment wherein the one or more porous support layers comprise first and second porous support layers adjacent the first and second sides of the filtration layer, respectively.

E4. A layered filter assembly as set forth in any preceding embodiment wherein said polyester is meltblown.

E5. A layered filter assembly as set forth in any preceding embodiment wherein said filtration layer is substantially free of polypropylene.

E6. A layered filter assembly as set forth in any preceding embodiment wherein one or more porous support layers are in contact with the filtration layer without an intermediate layer.

E7. A layered filter assembly as set forth in any preceding embodiment wherein the filtration efficiency of the assembly is at least 65% according to TSI 8130 using 0.3 micron particles at a flow rate of 5.3 cm/sec. E8. The layered filter assembly as set forth in any one of the preceding embodiments wherein the non-polypropylene melt blown polymer comprises fibers having two or more average fiber sizes of from 0.1 μm to 10 μm.

E9. The layered filter assembly as set forth in any one of the preceding embodiments wherein the non-polypropylene melt blown polymer comprises fibers having two or more average fiber sizes, said fibers comprising a first subset of fibers having an average diameter of from 0.1 μm to 3 μm and constituting at least 85% of said fibers.

E10. The layered filter assembly as set forth in any one of the preceding embodiments wherein the non-polypropylene melt blown polymer comprises a second subset of fibers having an average diameter of from 3 μm to 5 μm and constituting at least 15% of said fibers.

E11. A layered filter assembly as set forth in any preceding embodiment wherein the non-polypropylene melt blown polymer is polybutylene terephthalate.

E12. As beforeThe layered filter assembly of any of the preceding and subsequent embodiments, wherein the one or more porous support layers have a gas permeability of at least 500cfm/ft at 125Pa²。

E13. The layered filter assembly of any preceding or subsequent embodiment, wherein the gas permeability of the filtration layer is from 50 to 100cfm/ft at 125Pa²。

E14. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the filtration layer and the one or more porous support layers are laid across each other without an intermediate layer.

E15. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the filtration layer and the one or more porous support layers are joined at the filtration layer edge.

E16. The layered filter assembly as set forth in any one of the preceding and subsequent embodiments wherein the layered filter assembly further comprises one or more layers of hot melt adhesive, wherein the one or more layers of hot melt adhesive join the filter layer and the one or more porous support layers.

E17. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein one or more layers of hot melt adhesive are pre-laminated with the filtration layer.

E18. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the filter layer and the one or more porous support layers are joined at the edges of the filter layer by ultrasonic welding.

E19. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the filtration layer has a thickness of from 100 microns to 250 microns.

E20. The layered filter assembly of any preceding or subsequent embodiment, wherein the filtration layer has a basis weight in the range of 15g/m²To 50g/m²。

E21. The layered filter assembly as set forth in any one of the preceding and subsequent embodiments, wherein the filtration layer has a basis weight in the range of 22g/m²To 40g/m²。

E22. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the airflow resistance of the assembly ranges from 10Pa to 30 Pa.

E23. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the airflow resistance of the assembly ranges from 15Pa to 20 Pa.

E24. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein said layered filter assembly further comprises a sorbent layer; and a dielectric layer, wherein: the sorbent layer can be positioned between the filter layer and the dielectric layer; and one or more porous support layers are adjacent to the media and filter layers on opposite sides of the sorbent layer.

E25. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the media layer is a non-polypropylene meltblown polymer.

E26. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the media layer is a polyethylene terephthalate nonwoven.

E27. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the media layer is a nonwoven polyester formed by a carding, spunbond or meltblown process.

E28. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the media layer has a thickness of from 0.5mm to 1.3 mm.

E29. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the media layer has a thickness of from 1.0mm to 1.3 mm.

E30. A layered filter assembly as set forth in any preceding or subsequent embodiment wherein the sorbent layer comprises activated carbon.

E31. An article for filtering a closure, comprising a housing for holding an electronic device; a layered assembly disposed within the housing, the layered assembly comprising: a filtration layer comprising polyester comprising fibers having a non-uniform fiber size of 0.1 μ ι η to 10 μ ι η; and one or more porous support layers adjacent to the filtration layer.

E32. An article for filtering a closure as described in any of the preceding or subsequent embodiments, wherein the polyester layer is a polyester meltblown polymer.

E33. An article for filtering a closure as described in any of the preceding or subsequent embodiments, wherein the article further comprises a sorbent layer and a media layer; the adsorbent layer is positioned between the filter layer and the medium layer; and is

One or more porous support layers are adjacent to the media layers on opposite sides of the sorbent layer.

E34. An article for filtering a closure member as in any preceding or subsequent embodiment wherein the media layer has a lower air resistance than the filtration layer.

E35. An article for filtering a closure as described in any of the preceding or subsequent embodiments, wherein the dielectric layer is a polyethylene terephthalate nonwoven.

E36. An article for filtering a closure as described in any of the preceding or subsequent embodiments, wherein the layer of media is a polyester meltblown polymer having non-uniform fiber sizes ranging from 0.1 μm to 10 μm.

E37. An article for filtering a closure member as described in any of the preceding or subsequent embodiments, wherein the filtration layer is not an electret felt filter media.

Claims

1. A layered filter assembly comprising:

a filtration layer comprising polyester comprising fibers having a non-uniform fiber size of 0.1 μm to 10 μm, the filtration layer not being an electret felt filter media; and

one or more porous support layers adjacent to the filtration layer, wherein the fibers of the filtration layer have a multimodal size distribution comprising at least: a first average fiber diameter of 0.1-3.0 μm in 10-90% of the fibers and a second average fiber diameter of 3.0-10 μm in 90-10% of the fibers;

the fibers of the filter layer comprise polybutylene terephthalate.

2. The assembly of claim 1, wherein the one or more porous support layers comprise first and second porous support layers adjacent the first and second sides of the filtration layer, respectively.

3. The assembly of claim 1, wherein the size distribution of the fibers is bimodal.

4. The assembly of claim 1, wherein the polyester is a meltblown nonwoven.

5. The assembly of any one of claims 1-4, wherein the filter layer is substantially free of polypropylene.

6. The assembly of any one of claims 1-4, wherein the one or more porous support layers are in contact with the filtration layer without an intermediate layer.

7. The assembly of any of claims 1-4, wherein the fibers of the filtration layer comprise a non-polypropylene meltblown polymer.

8. The assembly of any of claims 1-4, wherein the first subset of fibers comprises at least 85% of the fibers.

9. The assembly of any one of claims 1-4, wherein the filter layer has a basis weight of 15g/m 2 to 50g/m 2.

10. The assembly of any one of claims 1-4, wherein the filter layer has a basis weight of 22g/m 2 to 40g/m 2.

11. The assembly of any one of claims 1-4, wherein the assembly has an airflow resistance of 10Pa to 30 Pa.

12. The assembly of any one of claims 1-4, wherein the assembly has an airflow resistance of 15Pa to 20 Pa.

13. The assembly of any one of claims 1-4, further comprising:

an adsorbent layer; and

a dielectric layer, wherein:

the adsorbent layer is positioned between the filter layer and the medium layer; and is

The one or more porous support layers are adjacent to the media and filter layers on opposite sides of the sorbent layer.

14. The assembly of claim 13, wherein the dielectric layer is a non-polypropylene meltblown polymer.

15. The assembly of claim 13, wherein the dielectric layer is a polyethylene terephthalate nonwoven.

16. The assembly of claim 13, wherein the sorbent layer comprises activated carbon.

17. The assembly of claim 13, wherein the sorbent layer comprises expanded polytetrafluoroethylene (ePTFE) and a sorbent material.

18. The assembly of any of claims 1-4, wherein the filter layer is electrically charged to enhance particle capture.

19. The component of any one of claims 1-4, wherein the component has a thickness of 100 μm to 250 μm.

20. An article for a filtration closure, comprising:

a housing for holding an electronic device; and

a layered filter assembly as defined in any one of claims 1 to 4 disposed in said housing.

21. The article of claim 20, wherein the housing is a hard disk drive closure.