Plastic and nonmetallic article shaping or treating: processes – Removal of liquid component or carrier through porous mold...
Reexamination Certificate
2001-02-26
2003-03-11
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Removal of liquid component or carrier through porous mold...
C264S087000, C264S122000, C264S320000
Reexamination Certificate
active
06531078
ABSTRACT:
BACKGROUND
The invention relates to the utilization of foam processes for making non-woven webs using particular raw materials, and for making particular end products. Foam processes are basically as described in U.S. Pat. Nos. 3,716,449, 3,871,952, and 3,938,782 (the disclosures of which are incorporated by reference herein), and in pending U.S. application Ser. No. 08/923,900 filed Sep. 4, 1997 and U.S. application Ser. No. 09/098,458 filed Jun. 17, 1998, the disclosures of all of which are also incorporated by reference herein.
Foam processes are normally used for making planar forms having a uniform thickness, i.e., two-dimensional shaped forms, during web formation. In accordance with the present invention, a three-dimensional shaped form is created by using a three-dimensional mold during web formation from one or more foam layers. Using a three-dimensional mold, e.g., a wire mesh mold, a pleated or grooved filter product, for example, can be formed directly from a foam having fibers or particles which, when applied to the mold, form the product. A wide variety of products can be produced using the foam processes and three-dimensional molds disclosed herein. For example, three-dimensional molds and foam processes are useful to produce a wide variety of filter products, including automotive pleated fluid and air filters, pleated heating and/or air conditioning (HVAC) filters, shaped breathing mask filters and bacterial filters, laminated cleaning products with super absorbent middle layers, such as a mop wipe shaped to fit a cleaning mop head, and other products.
The present invention can be used to eliminate subsequent mechanical pleating steps or milling steps previously used to create pleats and grooves in a two-dimensional planar web sheet created using two-dimensional planar molds and foam processes. In particular, the present invention obviates the prior art process of mechanically cutting grooves and other shapes to form a three-dimensional planar-shaped product after it has been formed using foam processes. The present invention avoids the prior need for process equipment that shapes the substantially planar intermediate web products formed from two-dimensional molds into a three-dimensional final product. The present invention is particularly suited for use in production of pleated and grooved filter papers, especially those having applications in automobiles.
The foam process of web making is used for making products, e,g., webs using particles or fibers, e.g., short cut fibers, synthetic fiber materials, fibers from mechanical cellulose wood pulp or chemical cellulose wood pulp, or other web materials. Utilizing the foam process, it is possible to produce three-dimensional, non-planar webs from a variety of fibers, particles or combinations of fibers and particles.
One application of the invention relates to the production of pleated or grooved filter paper, particularly for automotive use. Filter paper started to be used in automobiles some 40-50 years ago, and today is standard equipment in every car with a combustion engine. The applications for filter papers today can be divided into the following grade categories: auto air, oil, heavy-duty air (HDA), fuel media, and cabin air. The auto air media/filter paper is designed to trap the particles entering the engine with the air. The HDA filter paper has the same function, but is designed for a more demanding environment with large amounts of dust in the air (e.g., earth moving machines, etc.). An oil media/filter paper is designed to take the particles out of the oil stream entering the engine. The fuel media/filter paper is designed to filter particles from gasoline or diesel fuel before it enters the engine. The cabin air media/filter paper is designed to trap the outside particles before they come into the cabin or compartment where the passengers are sitting. There are also other applications for such filter papers.
Automotive filter papers have previously been produced according to wet-laid processes, which date back to the early part of the 1900s. In the wet-laid process, fibers are broken up under agitation in a pulper. The fibers are then pumped in a liquid slurry through deflakers and refiners to the paper machine. The deflakers and refiners disperse the fibers, and give them a better surface for generating bonding strength. The main components on the paper machine are the wet end and the dry end. Between the pulper and the wet end, various types of wet and dry strength enhancing chemicals are also added. The wet end comprises a headbox and dewatering elements. Typically the headbox has a flat fourdrinier, incline wire, or cylinder type foraminous element. The dewatering elements are designed to suck out water from the slurry to dewater it from roughly a 0.05% fiber consistency to a 25% fiber consistency on a moving wire (foraminous element). After the wet end, the media enters the dry end. The objective there is to dry the filter media from 25% to about a 98-99% fiber consistency.
The filter media is now either impregnated “on-line” on the same paper machine, or rolled up and impregnated “off-line” on a separate impregnation machine. The objective of the impregnation process is to fully saturate the media with a resin or latex (thermosetting or thermoplastic), and thereby give the media its final mechanical strength as well as making it convertible into a filter. The impregnation process basically includes an impregnation unit followed by dryers. The impregnation unit can be a size-press, roll coater, curtain coater, or the like, and the dryers can be any conventional contact
on-contact types. When the media reaches about a 10-15% moisture content, the oil and HDA media types are grooved, giving them a continuous S-shape in the machine direction. Grooving the media type increases the overall filtration surface and helps keep the subsequently formed pleats separated when pleating the media and building the filter element.
After impregnation the media is slit into various slit width sheets before packaging and sending to a customer. At the customer site, the media is mechanically pleated on conventional pleating machines giving the media its final physical configuration before building a filter element containing the filter paper. How the ends of the media are sealed, the media further polymerized, and which characteristics are particularly important, depend on the customer and end application, and these details are conventional.
The process of the U.S. patent application Ser. No. 09/098,458 discusses the manufacture of a planar sheet of filter paper by means of the foam process, and then subsequently the sheet is grooved and pleated to make the actual filter material. The present invention forms the filter paper on a mold, which is grooved, pleated, or grooved and pleated itself. There is no need to perform subsequent mechanical steps of pleating, grooving or otherwise imparting three-dimensional shapes to the web product extracted from the molding process.
Forming products from a fiber or particle foam is advantageous over wet-laid processes. For example, filter paper has been manufactured using a water-laid process. In that process, fibers in a liquid suspension are introduced onto a grooved mold. The depth of the liquid slurry is relatively shallow. Soon after the introduction of the fiber suspension, the slurry surface sinks below the top portion of the lower mold, losing the hermetic seal permitting suction from beneath the mold to avoid removing water from the fibrous slurry. When the seal is lost, the suction acts primarily on the portion of the mold having no contact with the suspended fibers. Consequently, the fiber formation at the bottom of the mold is slow and not optimal. Additionally, there is a possibility that the top portions of the mold would collect a smaller number of fibers than the bottom portions, because the fibers in the liquid slurry tend to settle and concentrate at the bottom of the mold. In contrast, the foam processes disclosed herein involve one or more layers of foam
George Jonathan
Grosso Andrea
Laine Eino
Rahiala Hanna
Rökman Kay
Ahlstrom Glassfibre Oy
Kuhns Allan R.
Nixon & Vanderhye P.C.
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