Patent Publication Number: US-2018044230-A1

Title: Preparation For Fiberglass Air Filtration Media

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/151,478, filed on May 10, 2016, now U.S. Pat. No. 9,695,084, which claims the benefit of U.S. Patent Application No. 62/179,572, filed on May 11, 2015. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to air filtration media and, more particularly, to air filtration media manufactured to a Minimum Efficiency Reporting Value (MERV) 8 rating and above with an initial pressure drop of less than or equal to 0.20 inches water gravity (WG). The MERV 8 rating and greater can be achieved with fiberglass media without the addition of an undesirable oil coating. 
     BACKGROUND 
     Today, fiberglass air filtration manufacturing methods and formulations can involve the use of oil added after the fiberglass media exits the curing oven to provide for increased entrainment of air contaminants such as dust and particulates. Present solutions handle the problem of capturing increased amounts of dust using the oil method. 
     The oil additive is undesirable since the oil makes the process more expensive in additive costs, handling costs, and environmental costs and is cosmetically undesirable. Binders are applied to the fibers as they are wound on the drum. Binder mixtures often are comprised of 65% urea formaldehyde and 35% water. In other methods, 1 butyl tackifiers may be mixed into a water emulsion and then mixed with a urea formaldehyde emulsion binder. Urea formaldehyde emulsion is typically used as a binder of glass fibers in the fiberglass filtration industry. 
     Other patents have mentioned the use of a dry tackifier binder such as polybutene added to a composition to create a tackifier for spraying fiberglass filtration media. For example, see Miller U.S. Pat. No. 6,136,058, entitled “Uniformly Tacky Filter Media,” and Miller U.S. Pat. No. 5,846,603, entitled “Uniformly Tacky Filter Media.” However, the addition of polybutene, while useful, does not reach the MERV 8 rating and higher. In fact, the addition of polybutene barely achieves a MERV 7 rating by itself and then not routinely. Modigliani U.S. Pat. No. 2,546,230, entitled “Glass Product and Method of Making the Same,” and Modigliani U.S. Pat. No. 2,729,582, entitled “Method for Making Unwoven Fabrics,” both mention the use of additives to the fiberglass media. However, in Modigliani U.S. Pat. No. 2,546,230, the binder cited is being utilized for fiber board insulation and is water mixed with urea formaldehyde resin with the addition of an acrylic resin. In Modigliani U.S. Pat. No. 2,729,582, the resin is a vinyltrichlorosilane in a 3.5% solution of xylol, which is not suitable for fiberglass filtration media, but rather more suitable for composites. This disclosure presents a composition that achieves and sustains a MERV 8 rating and higher. 
     MERV, Minimum Efficiency Reporting Value, commonly known as MERV rating, is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of filters. The scale “represents a quantum leap in the precision and accuracy of air-cleaner” and allows for improved health, reduced cost and energy efficiency in heating, ventilation and air conditioning (HVAC) design as well as increased efficiency. For example, a HEPA filter is often impractical in central HVAC systems due to the large initial pressure drop the dense filter material causes. Experiments indicate that less obstructive, medium-efficiency filters of MERV 7 to 13 are almost as effective as true HEPA filters at removing allergens, with much lower associated system and operating costs. In like fashion, the addition of a polymer compounded with a dry adherent and a resin binder provides for a filter media without a high initial pressure drop. 
     The scale is designed to represent the worst-case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range. 
     Shown in  FIG. 1  is a table grouping MERV ratings by particle size: 
     Prior techniques exist however for the addition of resins such as acrylate polymers to polyester pleat filtration media and binder (with no urea formaldehyde). However, acrylate polymers have never been combined with urea formaldehyde and polybutene and then applied to fiberglass filtration media. 
     It would be advantageous to provide a system and method of air filtration formation and media that increase dust holding capacity. 
     It would also be advantageous to provide a method of formation of MERV 8 or higher air filtration media with fiberglass that does not require the use of oil. 
     It would further be advantageous to provide a method of controlling the cross-sectional density of the fiber to maximize the dust holding capacity of the filter media while controlling the initial pressure drop. 
     It would also be advantageous to provide for a finished filter media that feels and looks different from fiberglass. 
     It would also be advantageous to provide for a fiber that is relatively soft, springy and dry to the touch, with fibers that look more like plastic than fiberglass. 
     Thus there remains considerable need for binder compositions that provide for less mess and are cosmetically more pleasing to customers while providing for increased dust holding capability at a MERV 8 or better. Additionally, the fiber should be capable of progressive density with a soft springy texture. 
     SUMMARY 
     In accordance with the present disclosure, there is provided a system and method of forming air filtration media that does not involve the use of an oil additive to fiberglass, yet creates a MERV filter rating of 8 or better. The manufacturing method of forming the air filtration media is mentioned in a co-pending U.S. patent application Ser. No. 14/181,426, filed on Feb. 14, 2014, which is incorporated by reference herein. 
     To achieve MERV 8 or better without undesirable oil additives, a polymer, wherein the polymer is one of a group of polymers consisting of acrylates and methyl acrylic acids, is added to a dry adhering agent consisting essentially of a group of polybutene during the fiberglass air filtration media formation. Both the polymer and the dry adhering agent mix in varying percentages with a resin binder (urea formaldehyde) and are applied to the fiberglass as it is spun onto a drum. In varying the application rates of the combined binder resin mixed with a polymer selected from a group of polymers formed from acrylic acid or methyl-acrylic acid and a dry adhering agent, e.g. polybutene in a specific formulation, so that the end result can be controlled with greater precision. 
     Various objects, features, aspects, and advantages of the present disclosure will become more apparent from the following description of the disclosure, along with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description makes reference to the accompanying figures wherein: 
         FIG. 1  shows a table grouping MERV ratings by particle size. 
         FIG. 2  depicts a chemical structure indicative of a selected group of acrylate polymers, consisting of a 1-butyl, a methyl, an n-butyl acrylate and others in a polymeric structure. 
         FIG. 3  depicts a chemical structure representative of the structures of acrylic and methyl-acrylic acid which are the basis of the methyl-acrylic polymers discussed herein. 
         FIG. 4A  shows an electron micrograph of a polymer discussed herein. 
         FIG. 4B  shows information presented by an analysis of the polymer by electron micrograph. 
         FIG. 5  is a chemical formula for the most common form of an acrylate polymer 10 utilized in one embodiment of this disclosure. 
     
    
    
     Other objects, features, and characteristics will become more apparent upon consideration of the following detailed description with reference to the accompanying figures. 
     DETAILED DESCRIPTION 
     The chemical structure shown in  FIG. 2  is the general structure that is indicative of a selected group of acrylate polymers, consisting of a 1-butyl, a methyl, an n-butyl acrylate and others in a polymeric structure. For purposes of comparison, the IUPAC lists this selection of acrylates as -prop-2-enoate (either butyl or methyl). The chemical reaction of a selected polymer with a dry adherent and a resin binder (which also acts as an additional adherent) creates a polymeric-based tackifying agent with substantial dust holding capabilities. Ingredients in the acrylates copolymer group all contain the monomers acrylic acid and methyl-acrylic acid or one of their salts or esters. The drawing shown in  FIG. 3  is more closely representative of the structures of acrylic and methyl-acrylic acid which are the basis of the methyl-acrylic polymers discussed. 
     These ingredients are considered similar in that they are uniformly produced in chemical reactions that leave very little residual monomer. Although residual acrylic acid may be as high as 1500 ppm, typical levels are 10 to 1000 ppm. Concentrations may be as high as 25% if used as a binder, film former, or fixative; or as low as 0.5% if used as a viscosity-increasing agent, suspending agent, or emulsion stabilizer. 
     Analysis of polymer 10 (shown in  FIG. 5 ) by electron micrograph presents the information shown in  FIGS. 4A and 4B . 
     The structure presented provides a desirable basis for binding and adhesive properties with the carbon and oxygen bonds being of the most significance with the sulfur presenting minimally in the base formulation. The sodium presents as a salt of the acrylic or meth-acrylic acid. 
     The dry adhering agent is a polymer of the group consisting essentially of 1-butene and 2-butene and isobutene. The structure of the 1-butene and the 2-butene is seen in the repeat units, where, in the case of 1-butene, the structure is: 
       -[—CH2-CH(CH2CH3)-] n -
 
     and in the case of 2-butene, the repeat unit structure is: 
       -[—CH(CH3)-CH(CH3)-] n -
 
     The C4 polymer typically includes various forms of butene, for example isobutene, 1-butene, 2-butene, and others, and can contain a small amount of propene and minor amounts of polymerization byproducts. For simplicity, the polymer is referred to herein as polybutene polymer. Typically, isobutene constitutes from about 80% to about 95% of the total polybutene polymer. The polybutene polymer has at least one double bond per molecule. 
     The thickness of the skinning of the fiberglass on the air outflow surface and the air inflow surface are controlled such that the skinning process on the air outflow can be densified while still maintaining an initial pressure drop of less than 0.20 WG for the finished fiberglass air filtration media. Furthermore, the skinning on the air inflow surface can be maintained as thin as varying needs require preventing stray fibers from projecting randomly from the surface. The fiber media between the two skins progressively increases in density such that the fiber on the air inflow is less dense than the fiber on the air outflow of the fiberglass filtration media. Progressive density is achieved by varying the speed of the traverses of the furnace over the drum. This density control is achieved in a substantially linear fashion. 
     After oven curing of the fiber, the finished media feels and looks different from normal fiberglass. It is relatively soft, springy and dry to the touch. The fibers look more like plastic than fiberglass, due in part to the polymeric spray mixture bound to the fiberglass media. The progressive density of the skin of the fiberglass filtration media along with the polymer, resin binder and the dry adhering agent mixture provide for increased dust holding capability by allowing for proper airflow and help to hold the initial pressure drop to 0.20 WG. 
     The addition of a polymer 10 combined with a dry adhering agent and resin binder increases the ability of the fibers to attract and hold dust such that a MERV 8 rating and above can be achieved with a sustainably low initial pressure drop of 0.20 WG. This is achieved with a fiberglass based media without the addition of an undesirable oil coating. The low initial pressure drop is due in part to the substantially linear progressive density of the fiberglass media coupled with the high dust holding capability. This prevents face loading of the skin surface by large particles. 
     As indicated in the enclosed drawing and discussion, the polymer 10 is an isotactic polymeric acrylate, which is sticky and typically used in formulations to aid in viscosity and ability to emulsify. In accordance with the present disclosure, there is provided a system and method of forming air fiberglass filtration media that does not involve the addition of oil during the fiberglass manufacture process. A spray composition is formed by combining an acrylate polymer 10 (consisting essentially of the group of polymers such as -prop-2-enoate), a dry adhering agent (a polybutene consisting essentially of a group of 1-butene, 2-butene, and isobutene), and a resin binder. The spray composition is applied during the fiberglass air filtration media formation, as the fiberglass is wound onto the rotating drum. The addition of a polymer 10 and varying percentages of the dry adhering agent with the resin binder mixture increases the dust holding capacity of the resulting fiberglass filtration media. 
     The progressive density of the fiberglass media progresses from a lower density of fiberglass media at the air inflow surface to higher density of the fiberglass media at the air outflow surface. In the preferred embodiment, the fibers are 21-25 microns with a median size of 23 microns. However, the principles disclosed herein may be used with fibers of other sizes. The progressive density of the fiberglass media, along with the application of the spray composition, acts to impede large particulate movement within the fiberglass media bulk. This increased impedance occurs between the two faces of the skin surfaces from the air inflow skin surface to the air outflow skin surface. These large particulates move less freely through the progressively denser fiberglass bulk and are trapped by the lower density in the region of the air inflow surface of the fiberglass media. This allows finer particles to be trapped in the higher density region of the air outflow surface and outflow side skin. 
     The spray composition (acrylates, polybutene, and urea formaldehyde) is applied without clogging and is applied to the fiberglass as it is spun onto a drum. The spray composition may comprise 55-79% urea formaldehyde, 20-40% polymer compound, and 1-5% polybutene. In the preferred embodiment, the spray composition comprises 67% urea formaldehyde resin, 30% polymer compound, and 3% polybutene. The spray composition along with the progressive density of the fiberglass media provides an excellent means to capture and hold large dust particulates while avoiding the face-loading of the media common in other types of filtration media. By varying application rates of the spray composition, a specific formulation can be achieved that provides for greater precision. 
     The density of the skin surfaces on the air outflow and air inflow can be controlled while still maintaining an initial pressure drop of less than 0.20 WG for the finished filter. The skinning on the air inflow surface can be maintained as thin as various needs require, preventing stray fibers from projecting randomly from the surface and facilitating glue adhesion in the customers&#39; filter framing processes. The fiber is then oven cured. After oven curing, the finished media feels and looks different from fiberglass. It is relatively soft, springy and dry to the touch. The fibers look more like plastic than fiberglass. 
     As disclosed herein, a fiberglass filtration media with the ability to attract and hold dust and achieve a MERV 8 rating and above, without the addition of an undesirable oil coating, is made possible by producing a fiberglass filtration media with progressively increasing density from air inflow to air outflow comprising thin filaments (for example, 21 to 25 microns) and adding polymer combined with a dry adhering agent and a resin binder (urea formaldehyde). 
     Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the examples chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of the disclosure herein.