Patent Application
20070289920
The present invention relates to filtration, and more particularly to a filtration medium and liquid filter for use in pool and spa filters.
Pools and spas typically include a filtration system through which the water is circulated to remove dirt, debris and other foreign matter. Many of the filtration systems utilize a replaceable filter cartridge of a generally cylindrical form containing a filter element of a pleated construction. The filter element is typically made of a pleated polyester nonwoven fabric material. One such nonwoven fabric material that has been in widespread use for a number of years is sold by BBA Fiberweb under the trademark Reemay® and comprises a spunbond nonwoven fabric formed of polyester filaments bonded together to form a coherent strong pleatable nonwoven fabric filtration medium.
It is typical for the filter cartridge to be removed periodically from the filtration system and cleaned, by rinsing with a garden hose, to remove accumulated dirt and debris trapped by the filter. Then the filter cartridge is replaced in the filtration system. This approach is labor intensive, and can result in poor filtration efficiency if the filter cartridge is reused too many times.
The present invention provides a filtration medium and a filter cartridge for pools and spas that has high filtration efficiency and is produced from low cost materials that allow for the filter cartridge to be a single-use filter that is disposed of when dirty and replaced with a new filter cartridge, rather than being cleaned and reused.
According to the present invention, the filter cartridge comprises a filter medium including a plurality of layers of a spunbond nonwoven fabric of continuous filaments. The filter medium may also include one or more additional layers such as a thermal or resin bonded carded nonwoven fabric, a hydroentangled nonwoven fabric or a fabric formed from caustic cotton fibers. The filter medium is formed into a pleated configuration. The filter medium may suitably comprise from 2 to 15 layers of the nonwoven fabric that are bonded to one another to form a relatively stiff multi-layer structure. The overall thickness of the filter medium is preferably from 0.25 to 3 mm.
In one advantageous embodiment of the invention, the filter cartridge includes a filter medium in the form of a plurality of layers of a composite nonwoven fabric laminate, wherein the laminate includes at least one spunbond layer and at least one additional nonwoven fabric layer. The layers of composite nonwoven fabric laminate are bonded together and formed into a pleated configuration.
In a more specific embodiment, the composite nonwoven fabric used in the filter medium is a spunbond-meltblown-spunbond (SMS) composite nonwoven fabric including outer spunbond layers formed of continuous filaments bonded to one another to form a spunbond nonwoven fabric and at least one interior layer of meltblown fibers between said outer spunbond layers. Each composite nonwoven fabric layer preferably has a basis weight of from 10 to 100 grams per square meter (gsm).
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
A filter cartridge of the type commonly used spa and pool filters is shown in
One embodiment of a filtration medium 20 in accordance with the present invention is shown in greater detail in
The liquid permeable nonwoven fabric 21 includes at least one nonwoven layer formed of continuous filaments. The continuous filament nonwoven fabric layer is a spunbond nonwoven fabric. Examples of various types of processes for producing spunbond fabrics are described in U.S. Pat. No. 3,338,992 to Kinney, U.S. Pat. No. 3,802,817 to Matsuki, U.S. Pat. No. 4,405,297 to Appel, U.S. Pat. No. 4,812,112 to Balk, and U.S. Pat. No. 5,665,300 to Brignola et al. In general, these spunbond processes include steps of extruding molten polymer filaments from a spinneret; quenching the filaments with a flow of air to hasten the solidification of the molten polymer; attenuating the filaments by advancing them with a draw tension that can be applied by either pneumatically entraining the filaments in an air stream or by wrapping them around mechanical draw rolls of the type commonly used in the textile fibers industry; depositing the attenuated filaments randomly onto a collection surface, typically a moving belt, to form a web; and bonding the web of loose filaments. The continuous filaments are bonded to each other at points of contact to impart strength and integrity to the nonwoven web. The bonding can be accomplished by various known means, such as by the use of binder fibers, resin bonding, thermal area bonding, calendering, point bonding, ultrasonic bonding and the like. The filaments are bonded to each other at points of contact, but the nonwoven structure remains sufficiently open to provide the requisite air and water permeability.
In the embodiment shown in
In one advantageous embodiment, the liquid permeable nonwoven fabric is a composite nonwoven fabric, and in a more specific embodiment, each layer of the composite nonwoven fabric comprises a spunbond-meltblown-spunbond (SMS) composite laminate, including outer layers of spunbond nonwoven fabric formed of continuous filaments and at least one interior layer of meltblown microfibers. Exemplary spunbond-meltblown-spunbond composite laminates are described in U.S. Pat. Nos. 4,041,204 and 5,108,827.
Thus, as shown in
Preferably, the spunbond nonwoven fabric layers and the meltblown layers are formed of a synthetic fiber-forming polymer which is hydrophobic in nature. Suitable polymers include polypropylene, polyethylene, polyester, and polyamide. Among the well known synthetic fiber-forming polymers, polyester polymers and copolymers are recognized as being suitable for producing hydrophobic nonwoven webs that are resistant to degradation from chlorine and bromine based chemical used in pool and spa water treatment.
Each layer of composite nonwoven fabric laminate 21′ may have a basis weight of from 10 to 200 grams per square meter (gsm), and more desirably from about 34 to 100 grams per square meter. The continuous filaments of the spunbond nonwoven fabric layers preferably have a denier per filament of approximately 1 to 10 and the filaments can have a cross-section ranging from round to trilobal or quadralobal or can include varying cross-sections and varying deniers. In some embodiments, at least one of the spunbond nonwoven layers of the composite nonwoven fabric laminate includes sheath-core bicomponent filaments. The sheath component of the sheath-core bicomponent filaments may suitably be formed from a lower melting polymer than the core component. For example, the core component may be formed from polypropylene and the sheath component from polyethylene. Optionally, an antimicrobial agent can be incorporated into the sheath component.
The filtration medium 20, 20′ may suitably comprise from 2 to 15 layers of the nonwoven fabric 21, 21′ that are bonded to one another to form a relatively stiff multi-layer structure. The overall thickness of the filter medium is preferably from 0.1 to 3 mm. The thickness of the filtration medium affects both its filtration characteristics and its pleatability. Too thin a medium will result in the filtration taking place primarily at the fabric surface. The filter will be easier to clean, but it will clog much more quickly. Thicker materials provide some depth filtration along with surface filtration, which will extend the time required between cleanings. Thickness also affects the pleating and the quality of the final pleat, since fabric thickness is directly related to stiffness. Overly thin materials will not have sufficient stiffness to retain a pleat, and the pleats will tend to collapse upon themselves. Overly thick materials are so stiff that they will form poor pleats or will tend to return to the original unpleated configuration.
To assist in achieving the desired stiffness, the filtration medium 20, 20′ may include, in addition to the nonwoven fabric layers 20, 20′, one or more stiffening layers bonded to the layers of composite nonwoven fabric laminate. The stiffening layer may comprise at least one structure selected from the group consisting of spunbond nonwoven fabrics, carded thermal bond nonwovens, carded resin bond nonwovens, hydroentangled nonwovens, scrims, nets and apertured films.
Preferably, the filtration medium includes from 2 to 15 individual layers of composite nonwoven fabric, more desirably 3 to 6 layers. To provide sufficient stiffness for pleating, the overall thickness of the filtration medium is preferably from about 0.1 to about 3 mm, and more desirably from 1 to 2 mm.
The stiffness of the filtration medium may be quantified using industry standard test instruments, such as the Handle-O-Meter which measures flexibility (or conversely for the purposes of the present invention, stiffness) of sheet materials such as nonwovens in accordance with ASTM D 2923 or the Association of the Nonwovens Fabrics Industry (INDA) standard test method IST 90.3. Handle-O-Meter measurements are made on an instrument by the Thwing-Albert Instrument Co. of Philadelphia. The measurements are the force in grams to push a 100 mm wide fabric into a slot which is 100 mm wide. In conducting the Handle-O-Meter measurements, the fabric is tested from both the top and the bottom and in both the machine direction and the cross direction and the results are averaged. The filtration medium 20 preferably has a Handle-O-Meter stiffness of at least 5 grams, and more desirably at least 10 grams, and for certain applications more desirably at least 18 grams.
The permeability of the nonwoven fabric substrate may be conveniently evaluated by measuring its air permeability using a commercially available air permeability instrument, such as the Textest air permeability instrument, in accordance with the air permeability test procedures outlined in ASTM test method D-1117. Preferably, the nonwoven fabric substrate should have an air permeability, as measured by this procedure, of from 20 to 270.
The following non-limiting examples are provided for purposes of illustrating various embodiments of the present invention.
A composite nonwoven fabric laminate is produced on an integrated spunbond-meltblown-spunbond manufacturing line having successively arranged melt extrusion beams for producing a first spunbond nonwoven outer layer, up to three nonwoven intermediate layers of meltblown microfibers, and a second spunbond nonwoven outer layer. Patterned calender rolls are provided downstream from the last spunbond extrusion beam for bonding the respective layers together to form an integral point bonded nonwoven fabric laminate. The spunbond outer layers each have a basis weight of 10 gsm and are formed of polypropylene continuous filaments. Three intermediate layers of polypropylene meltblown microfibers are produced having a total basis weight of 34 gsm. The resulting spunbond-meltblown-meltblown-meltblown-spunbond (SMMMS) laminate has an overall basis weight of 88 grams per square meter (2.6 ounces per square yard), a thickness of 0.4 mm and a stiffness of 55 grams when tested on a Handle-O-Meter according to IST 90.3 (95).
Seven layers of the composite nonwoven fabric laminate of Example 1 are stacked together face-to-face relation and bonded together by a sonic bonding apparatus. Here, sonic energy is used to generate discrete point bonds from a highly engraved roll to form a pleatable composite laminated filtration medium.
To provide further stiffness to the filtration medium, a 57 grams per square meter polypropylene spunbond nonwoven fabric produced by BBA Fiberweb under the trademark Typar® is placed on one side of the seven-layer laminate of Example 2 and sonic bonded to the seven-layer laminate.
A stiffened filtration medium is produced as in Example 3, except that the Typar® nonwoven stiffening member is replaced by an open-mesh scrim netting of polypropylene produced by Conwed Plastics of Minneapolis, Minn.
The filtration medium of Example 3 is pleated with a push-bar type pleater to form one inch pleats, and the pleated filtration medium is formed into a cylindrical filter cartridge of the configuration shown in
A spunbond nonwoven fabric of 34 grams per square meter basis weight is formed from polypropylene continuous filaments of 1 to 2 denier per filament. The nonwoven fabric is point bonded using an engraved calender roll with a 20 percent bond area. Ten layers of the spunbond nonwoven fabric are stacked together face-to-face along with a polypropylene open-mesh scrim netting on one side. This assembly is sonic bonded together using a sonic bonding apparatus as described in Example 2 to form a pleatable filtration medium. This filtration medium is pleated and formed into a cylindrical filter cartridge of the configuration shown in
Five layers of the SMMMS laminate of Example 1 are combined as the center component of a filtration medium along with outer layers formed of 34 gsm spunbond nonwoven fabric formed of sheath-core bicomponent filaments having a polyethylene sheath and a PET core. The respective layers are sonic bonded together.
A filtration medium is produced as in Example 7, except that a triclosan antimicrobial agent from Microban Inc. is blended into the polyethylene sheath component of the bicomponent fibers at a concentration of 2% by weight of the polyethylene.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
| Number | Date | Country | |
|---|---|---|---|
| 60747116 | May 2006 | US |
