WO2014062943A1 - Low-emission binder for muffler preform - Google Patents

Abstract

A low-emission binder composition is provided for use in a glass fiber muffler preform. The low-emission binder composition comprises a predominantly inorganic material and an optional cross-linking agent. The low-emission binder composition has an LOI of no greater than 1.0 percent.

Description

LOW-EMISSION BINDER FOR MUFFLER PREFORM

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisional application nos. 61/715,022, filed on October 17, 2012, titled "Low Emission Binder for Muffler Preform", which is incorporated by reference in its entirety.

FIELD

[0002] The present invention relates generally to binder compositions, and more particularly to low-emission binder composition for forming compacted glass fiber muffler preforms.

BACKGROUND

[0003] Acoustical sound insulators are used in a variety of applications where it is desired to reduce noise emissions by dissipating or absorbing sound. For example, a sound absorbing material may be used in the exhaust mufflers of internal combustion engines to dampen or attenuate sound made by the engine exhaust gases as they pass from the engine through the exhaust system and into the atmosphere. Typically, continuous glass fiber strands are positioned internally in a muffler as the sound absorbing material. Continuous glass fibers are preferred over other fibers, such as chopped glass fibers, because the length of the continuous fibers decreases the possibility that free fibers may dislodge from the muffler and exit into the atmosphere.

[0004] Continuous glass fiber strands may be positioned in a muffler by a variety of methods known in the art. For example, continuous glass fiber strands may be inserted directly into a muffler shell, such as is disclosed in U.S. Pat. No. 4,569,471 to Ingemansson et al. In particular, Ingemansson et al. disclose a process and apparatus for filling muffler shells by feeding continuous multifilament glass fiber strands through a nozzle and into a muffler outer shell. Compressed air is used to expand the fiber strands into a wool-like material inside the shell.

[0005] Alternatively, fibrous filled bags may be utilized to fill the inner cavities of a muffler. This process for filling a muffler shell with continuous glass fiber strands includes filling a bag with continuous glass fibers and inserting the bag into a muffler cavity. The bag is positioned adjacent to an internal structure located within a first muffler shell part. A partial vacuum is applied to draw the filled bag towards the internal structure. A second muffler shell part is then placed adjacent to the first muffler shell part such that the first and second muffler shell parts define an internal cavity containing the internal structure and the fibrous material-filled bag.

[0006] In addition to filling a muffler shell with continuous glass fiber strands, it is also known in the art to form preforms of continuous glass fiber strands which are adapted to be inserted into a muffler shell. U.S. Pat. No. 5,766,541 and EP 0941441 to Knutsson et al. disclose a preform of continuous glass fiber strands made by feeding continuous glass fiber strands into a perforated mold to form a continuous wool product in the mold, feeding a binder into the mold, compressing the mold to compact the wool product to a desired density, heating the mold to cure the binder, and removing the preform from the mold. The preform may then be inserted into a muffler cavity.

[0007] In U.S. Patent Publication No. 2001/0011780 Al and EP 0692616 also to Knutsson, continuous glass fiber strands and a powder binder, particularly a phenolic binder, are blown into a cavity formed of a perforated screen having the shape of the muffler to be filled. Hot air is then passed through the perforated screen to cure the binder and bond the fibers together. Next, cool air is circulated through the screen to cool the preform so that it can be removed from the screen and inserted into a muffler.

[0008] In many of the methods in existence for forming muffler preforms, a binder is applied to the fibers prior to filling a muffler mold with the fibers. Generally, the binder is sprayed onto the glass fibers during the texturization of the fibers to form a wool-like material. The binder conventionally used in muffler preforms is a thermosetting, phenolic-based resin. The phenolic-based resin is in a powder form and is sprayed onto the fibers with water to reduce dusting and aid in helping the powder to stick to the glass fibers before curing. After curing, thermosetting binders generally form cross-linked products through irreversible cross-linking reactions. Thus, once the binder contacting the fibers is cured, such as in an oven, the cured binder holds or retains the fibers in the shape of the preform until the preform is installed into a muffler shell.

[0009] Phenolic-based binders, such as are used in continuous glass fiber strand preforms for mufflers decompose when exposed to high temperatures and may emit emissions, such as volatile organic compounds (VOCs) and other air pollutants during their decomposition. [0010] The pollutant emissions from vehicles are strictly regulated by emission standards that set forth specific limits to the amount of pollutants that can be released into the environment. Europe has implemented the European Emission Standards, which defines the acceptable limits for exhaust emissions of new vehicles sold in EU member states and is adopted by a number of other countries to guide emission regulations. Particularly, the EURO standards regulate emissions of nitrogen oxides (NO_x), total hydrocarbons (THC), non-methane hydrocarbons (NMHC), carbon monoxide (CO) and particulate matter (PM) for most vehicle types. The most recent EURO 6 standards are set to enter in force in September 2014 and all vehicles in relevant jurisdictions equipped with a gasoline or diesel engine will be required to meet these standards.

[0011] Therefore, there exists a need in the art for a low or zero emission binder composition that is environmentally friendly and reduces the emission issues seen with phenolic-based binders.

SUMMARY OF THE INVENTION

[0012] The general inventive concepts include a low-emission binder composition for use in a glass fiber muffler preform. The inventive low-emission binder composition comprises a predominantly inorganic material. The predominantly inorganic material may comprise one or more of clay, hydraulic cement, pure sulfoaluminate, colloids, silicates, phosphates, chemically bonded phosphate-based ceramics (non-hydraulic ceramic), poly(propylene carbonate); polymeric silicones, and poly(siloxanes).

[0013] In some exemplary embodiments, the low-emission binder composition meets as the

EURO 6 emission performance guidelines when exposed to high temperatures

[0014] The general inventive concepts further include a method for forming a preform product. In some exemplary embodiments, the method includes applying a low-emission binder composition to a plurality of fibers, filling the mold cavity with the binder-coated fibers, and curing the fibers at a temperature between about 150 and 500 °C.

[0015] In accordance with some exemplary embodiments, the fibers are texturized glass fibers.

[0016] In some exemplary embodiments, a preform product is formed by the method described above.

[0017] In some exemplary embodiments, the preform produced meets the emission standards set forth in the EURO 6 performance guidelines. [0018] The foregoing and other objects, features, and advantages of the general inventive concepts will become more readily apparent from a consideration of the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 illustrates a partially exploded perspective view of an exemplary embodiment of a mold for forming a preform for a muffler.

[0020] Figure 2 illustrates an exploded cross-sectional view of the mold in Figure 1 along line 3-3.

[0021] Figure 3 illustrates a cross-sectional view of the mold illustrated in Figure 1 showing the nozzle introduced into the mold assembly.

[0022] Figure 4 illustrates a cross-sectional view of the molds illustrated in Figures 1 and 3 showing the mold partially filled with texturized glass fibers.

[0023] Figure 5 illustrates a cross-sectional view of the mold illustrated in Figures 1, 3, and 4 showing the mold filled with texturized glass.

[0024] Figures 6(a) and (b) illustrate an exemplary texturizing nozzle that may be used in accordance with the method of the invention.

[0025] Figure 7 illustrates a perspective view of an exemplary muffier preform formed in accordance with the method of the invention.

[0026] Figure 8 graphically illustrates a plot of the weight of a poly(siloxane) sample vs. temperature.

[0027] Figures 9(a) and (b) graphically display the weight % loss vs. temperature of a poly(siloxane) resin binder composition.

[0028] Figures 10 (a) and (b) graphically display the weight % loss vs. temperature of a phenolic resin binder composition.

[0029] Figures 11 (a)-(d) illustrates exemplary dust testing air samplers.

[0030] Figure 12 graphically illustrates the dust content produced vs. the binder content for exemplary binder materials.

[0031] Figure 13 graphically illustrates the dust content produced for exemplary binder compositions.

[0032] Figure 14 graphically illustrates the compressibility for preforms produced using various binder compositions as a function of the binder content.

[0033] Figure 15 graphically illustrates the compressibility for preforms produced using poly(siloxane) as a function of the binder content.

[0034] Figure 16 illustrates an exemplary sound absorbance test tube filled with glass fibers. [0035] Figure 17 graphically illustrates the effect of various exemplary binder compositions on the absorption coefficient at various frequencies.

DETAILED DESCRIPTION

[0036] The present invention will now be described with occasional reference to the specific embodiments of the invention. This invention may, however, be embodied in 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 be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0038] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from error found in their respective measurements.

[0039] As used in the description of the invention and the appended claims, the word/phrase "texturized fiber" is defined as glass strands wherein compressed air has separated the fibers forming the strands into individual fibers to give the fibers a "fluffed-up" or wool-like appearance. Additionally, the fibers can be "texturized" by other means, such as through mechanical handling of the fibers.

[0040] Various exemplary embodiments of the present invention relate to the formation of a low-emissions preform product or preform for a muffler. In one exemplary embodiment, the preform is formed by introducing texturized fiber strands into a mold cavity and applying a low-emission binder composition to the texturized fibers. The low-emission binder composition may be applied to the fibers either prior to, or post-introduction of the fibers into the mold. Suction may be applied simultaneously from an end surface and an interior of the mold cavity. Preforms formed in accordance with the method described herein are capable of being incorporated into vehicle exhaust systems to function as acoustic attenuators.

[0041] In accordance with some exemplary embodiments, the fibers are texturized and coated with the low-emission binder composition in a single step. As bundles of glass fibers are fed into a texturizing nozzle in which an airstream creates turbulence that imparts a slight bulk, the low-emission binder composition may be simultaneously sprayed onto the strands. Therefore, as the glass fiber bundles are being broken apart, the individual glass fibers are coated with the low-emission binder composition. The binder coated, texturized fibers may then be introduced into a mold cavity and cured to form a preform.

[0042] Referring now to the drawings, there is shown in Figures 1 through 5, an exemplary mold 16 for forming a preform 18 for a muffler, in accordance with one aspect of the invention. The illustrated exemplary mold 16 includes a first or outer mold portion 20 and a second or inner mold portion 22. A substantially annular space or mold cavity 24 is defined between the inner and outer mold portions, 22 and 20, respectively. In the illustrated embodiment, the mold portions 20 and 22 include a plurality of apertures 26 formed there through. Any desired number of apertures 26 may be formed through the mold portions 20 and 22. For example, in the illustrated embodiment, the apertures 26 cover about 50 % of the surface area of the mold portions 20 and 22.

[0043] The illustrated exemplary mold portions 20 and 22 may be formed from any suitable material. Examples of suitable materials include steel, engineered plastics, aluminum, and other suitable metals and non-metals. Any other substantially rigid material may also be used. If desired, the outer mold portion 20 may be formed of mesh material, such as wire mesh, to maximize the amount of surface area of the outer surface 92 that is open. Alternatively, one or both the outer mold portion 20 and the inner mold portion 22 may be formed of a supported mesh material, e.g., the mesh material could be wrapped around substantially rigid rods or bars which provide a support for the mesh material.

[0044] A mold lid 50 includes a substantially annular body 80 with an outwardly extending handle 82 (upwardly extending when viewing Figures 1 and 2). The body 80 has a planar first surface 84 (lower surface when viewing Figure 2) and a centrally formed opening 86 having a diameter slightly larger than the outer diameter of the inner mold portion 22. The planar first surface 84 is structured and configured to engage and compress an upper surface 19 of a preform 18. It will be understood that the handle 82 is not required. Alternatively, the surface 84 of the lid 50 may have any desired shape, such as conical or frustoconical.

[0045] The outer diameter of the body 80 is slightly smaller than the inner diameter of the outer mold portion 20. The body 80 is structured and configured to be mounted within the outer mold portion 20 and about the inner mold portion 22. In the illustrated embodiment, locking pins 48 are mounted to the body 80 and extend radially inwardly into the opening 86. The pins 48 are structured and configured to engage the slots 46 of the closed end 40 of the inner mold portion 22. It will be understood that the lid 50 may be secured to the mold 16 by any other desired means, and further may be secured to either or both of the inner mold portion 22 or the outer mold portion 20.

[0046] Referring now to Figure 3, the mold 16 is illustrated prior to receiving continuous strands 94. In the illustrated embodiment, continuous strands 94 are supplied from a doff (not shown) to a strand feeder 96. The strand feeder 96 may include one or more strand feeding mechanisms that feed one or more continuous strands 94 of glass fibers into a texturizing nozzle 98 of a texturizing device, such as the texturizing nozzle of the Silentex® system by Owens Corning described in U.S. Pat. No. 5,976,453. The strand feeder 96, texturizing nozzle 98 and nozzle extension 99 are schematically illustrated in Figure 4.

[0047] To fill the mold cavity 24 with a desired amount of glass fibers, the nozzle extension 99 is moved into (downwardly when viewing Figure 4) the mold cavity 24 in the direction of the arrow 1 14 until an outlet end 102 of the nozzle extension 99 is positioned in the mold cavity 24 at a depth of within the range of from about 1/2 to about 3/4 of the length of the mold cavity 24. The feeder 96 controls the speed or rate at which the continuous glass strands 94 are fed into the nozzle 98. The feeder 96 may include a metering device to measure and control the amount of the continuous glass strands 94 that are inserted into the mold cavity 24. The depth that the nozzle extension 99 is inserted into the cavity 24 may also be determined as a function of the number and size of the holes 60 in the flange 52 and the suction provided by the vacuum source 76.

[0048] The glass used to form the continuous strands 94 may be any type of glass suitable to withstand the temperatures present in the muffler. In dissipating the sound from internal combustion engines, the exhaust gases require the use of high temperature fibers. For example, suitable glass fibers may include E-type glass fibers, H-Glass fibers, S-type glass fibers, and Advantex® glass fibers. Alternatively, other types of heat resistant continuous fibers such as mineral fibers, (i.e., continuous basalt fibers) may be used. If high temperatures are not present in the muffler, synthetic fibers such as polyamide, aramid, polyaramid, and/or polypropylene, and the like may be used and/or comingled with the glass fibers to form the preform product. Glass fibers are often used in mufflers for internal combustion engines because of their sound attenuation capability, chemical resistance to the engine exhaust condensates present in a muffler, and resistance to the extreme heat conditions, such as those produced within a muffler.

[0049] The glass fibers may be coated with a conventional sizing composition, which allows the fibers to unwind and expand or fluff when blown with air. Generally, the sizing composition may include a carrier solvent, such as water, a coupling agent, a film former, and optional additives.

[0050] Referring again to Figure. 4, the nozzle extension 99 blows texturized glass fibers 95 into the mold cavity 24 through the first end 28 of the outer mold portion 20. The air may be pressurized by a conventional compressor and supplied by a hollow conduit in direct communication with the nozzle extension 99. As the texturized glass fibers 95 are fed into the mold cavity 24 through the texturizing nozzle 98, the expansion of the air flow separates the fibers forming the glass strands and entangles the individual fibers to give the fibers a "fluffed-up" or wool-like appearance (i.e., texturized the glass fibers). It will be understood that although the illustrated embodiment depicts the use of texturized glass fibers, non- texturized glass fibers may alternatively be used to form a preform product.

[0051] An exemplary texturizing nozzle 98 is further illustrated in Figures 6(a) and (b), which provides a means for texturizing the fibers and applying a binder to the fibers in a single continuous step. In accordance with one exemplary embodiment, a metered amount of continuous glass fibers and compressed air are introduced into the texturizing nozzle. The venturi effect of the air in the nozzle pulls the glass strands directly off a doff. Simultaneously, a binder composition is prepared in a container and then pumped, via a pressurized pump, into the texturizing nozzle 98, such that at any point along the texturization process, or after, the binder composition may be applied to the glass fibers. Particularly, in some exemplary embodiments, the low-emission binder composition is introduced into the texturizing nozzle 98 via a port 101 extending from the nozzle body. As the binder composition enters the nozzle, the pressure from the pump causes the binder composition to be distributed essentially evenly throughout the nozzle. Therefore, the glass fibers may be texturized and a binder composition may be applied to the glass fiber in a single, continuous step, rather than requiring multiple, discontinuous steps.

[0052] As used herein, a "low-emission binder composition," is meant to include a binder composition that, when used in formation of a vehicle muffler, causes the vehicle to release low, preferably zero emissions, as defined by the EURO 6 emission performance guidelines. The EURO 6 guidelines take into account potentially harmful types of vehicle gas emissions, such as carbon monoxide (CO), mass of hydrocarbons (HC), mass of oxides of nitrogen (NOx), and mass of particulate matter (PM). Such low-emission binder compositions, when exposed to high temperatures up to 1000 °C demonstrate the following properties: a mass retention of at least 60 weight % and a loss on ignition of no greater than 1.0 %.

[0053] The low-emission binder composition may comprise a single material or multiple materials. For example, the low-emission binder composition may comprise a low-emission resin, or a low-emission resin in combination with another material(s). In some exemplary embodiments, the low-emission resin is combined with a material that promotes cross- linking, such as a catalyst. The cross-linking material may be a liquid, emulsion, solution, when mixed with the resin, which becomes part of the final binder composition.

[0054] In some exemplary embodiments, the low-emission resin may comprise a predominantly inorganic material. For example, in some exemplary embodiments, the binder composition comprises one or more of clay; hydraulic cement, such as MgO/MgP0₄, calcium aluminate cement, calcium sulfoaluminate cement, and phosphoric acid based cement; pure sulfoaluminate; colloids, such as colloidal silica and colloidal alumina; silicates, such as silicate solution, lithium polysilicate, and potassium silicate; phosphates, such as phosphoric acid and aluminum phosphate; chemically bonded phosphate-based ceramics (non-hydraulic ceramic), poly(propylene carbonate); polymeric silicones; and siloxanes, such as poly(siloxane), and silicone resin, such as in the form of a powder, flake-like material, flakes, emulsion, viscous oil, and water soluble. In further exemplary embodiments, the low- emission binder may comprise one or more of sodium silicate, monoaluminum phosphate ("MAP"), and/or poly(siloxane).

[0055] The low-emission binder composition may include additives that closely mimic the chemistry of the glass. For instance, including calcium oxide in an MAP based binder composition may reduce the chemical attack of the binder on the glass. In particular, the concentration gradient of calcium oxide across the glass fiber - binder interface is important. In the absence of calcium oxide in the binder formulation, calcium oxide may leach out of the glass fiber readily to react with the MAP and may weaken the glass fiber.

[0056] Additionally, in some exemplary embodiments, the low-emission binder composition has a loss on ignition (LOI) that is close to the LOI of the glass itself, or the glass plus sizing composition. The LOI of the binder composition indicates the amount of binder lost when used in a preform that is heated in an oven to temperatures of about 500 °C. For example, an exemplary glass fiber coated with a sizing composition has an LOI of about 0.35 % to about 0.5 %. Therefore, the low-emissions binder composition preferably has an LOI that is close to 0.35 - 0.5%. In some exemplary embodiments, the LOI of the low emission binder composition is no greater than about 1.0 %, or no greater than about 0.6 % . In contrast, phenolic binders generally have LOIs ranging from about 3.0 to about 4.0 %, indicating significant weight loss due to emissions.

[0057] In some exemplary embodiments, the low-emission binder composition is a silicone- based binder composition. Silicones are a versatile class of materials that possess excellent chemical and thermal properties. Exemplary silicone materials may include silicone emulsions, silicone flake, and siloxanes. A silicone binder material enables the formation of a product that possesses both high tensile strength and flexibility, which results in desirable handling characteristics. There are a variety of ways in which silicones can be applied to texturized glass fiber: silicone flakes could be applied directly, the silicone could be dissolved in organic solvent and sprayed, or pre-cursors can be applied and the formation of the silicone resin can be accomplished in-situ.

[0058] One class of silicones, poly(siloxanes), comprise inorganic silicones that are curable at ambient temperatures, have high solids and low VOC, excellent temperature resistance, and good resistance to certain acids and solvents. Poly(siloxanes) are polymeric structures that contains repeating silicon-oxygen groups in the backbone, side chains, or cross-links. Poly(siloxanes) are a hybrid of organic and inorganic chemistry The presence of certain organic groups attached to the silicon atom in silicone and poly(siloxane) binders moderates the physical, chemical, and mechanical properties of the composition.

[0059] In some exemplary embodiments, the poly(siloxane) comprises one or more of a polyhydrogenmethylsiloxane, a carbosiloxane, a siloxane, or mixtures thereof.

[0060] The poly(siloxane) material according to some exemplary embodiments is in the form of a solvent-free polymer mixture. In some exemplary embodiments, a cross-linking catalyst is added to the polymer mixture in an amount from 0 to about 5 weight %. In some exemplary embodiments, the catalyst is included in no greater than 1 weight %. The cross- linking catalyst solution may comprise any catalyst desired for a particular application. In some exemplary embodiments, the cross-linking catalyst solution includes ethanol, a platinum and/or peroxide solution. In some exemplary embodiments, the low-emission binder comprises about 95 to 99.99 weight % poly(siloxane) and about 0.01 to 5.0 weight % catalyst, or from about 99 to 99.97 weight % poly(siloxane) and about 0.03 to 1.0 weigh % catalyst. [0061] In some exemplary embodiments, the poly(siloxane) comprises a low viscosity liquid silicone rubber resin system that undergoes a hydrosilation reaction in the presence of a platinum catalyst to yield a green body, which can be further processed into ceramic parts. Mixing the platinum catalyst with the polymer material forms an easily workable, strong binder composition that is cross-linked to provide "green-strength," in which the part takes on a shape and part integrity.

[0062] Alternatively, the low-emission binder composition may be cured using any curing method known and used in the art, such as, for example, UV- initiated curing, electron-beam curing, gamma ray curing, and other known curing processes.

[0063] In other exemplary embodiments, the low-emission binder composition may includes silicates. Commercial soluble silicates have the general formula of M₂0 * mSi0₂ * nH₂0, where M is an alkali metal and n and m are moles of silica and water per mole of M₂0, respectively. Exemplary silicates may include sodium silicates, potassium silicates, and lithium silicate.

[0064] Sodium silicates are formed by fusing sand (Si0₂) with sodium (or potassium) carbonate at about 1100-1200 °C. The resulting glass may be dissolved with high pressure steam to form a clear liquid known as "water glass" or spray dried to form quick dissolving, hydrous powders. The silicate's glassy nature imparts strong and rigid physical properties to a dried film or coating. Heating dried silicates above 250 °C will result in an essentially insoluble product under ambient conditions.

[0065] Sodium silicate binders may be set using a variety of methods, such as the removal of water (drying), neutralization of the metal oxide, and the addition of multivalent ions. To dry a sodium silicate binder, the Si-OH moieties undergo a dehydration reaction that results in an insoluble network of Si-O-Si bonds. Neutralization of the metal oxide is possible via the addition of an acid. The acid/base reaction removes the metal oxide from the solution, reducing the solubility of the silicate. In one neutralization approach, C0₂ dissolves in the silicate solution, forming carbonic acid, which reacts with the soda to form sodium carbonate (Na₂C0₃). Other acid producing compounds may alternatively be used such as aliphatic organic esters. With regard to setting via the addition of multivalent metal ions, such ions have a larger charge density, which significantly reduces the solubility of the silicate, causing the material to set.

[0066] When incorporating sodium silicate as a binder composition, it may be beneficial to include additional components, such as a surfactant, for example a silicate-compatible surfactant such as a non-ionic surfactant, clay, acid, starches, and silica gel. Particularly, since sodium silicate generally has a high pH of about 11.3, including clay with the sodium silicate may reduce the alkali level at elevated temperatures and reduce the corrosion of glass. Incorporating about 1-5% starches may be used to plasticize the binder. Silica gel provides the ability to increase the ratio of silica to soda in the formulation, which helps to minimize the chemical attack on glass. Latex may also be included to improve flexibility. Finally, substituting sodium with a heavier metal, may reduce the moisture sensitivity of the binder and helps to maintain the strength of the glass fibers.

[0067] In some exemplary embodiments, the sodium silicate binder composition comprises about 70 to about 100% Na₂0/Si0₂, 0 to about 30% colloidal silica, and 0 to about 50% clay. The ratio of silica to soda in Na₂0/Si02 is generally about 2-7, particularly about 3-6. In some exemplary embodiments, the ratio of silica to soda is about 3.55 to 5. Including silica gel in the binder composition may increase the ratio of silica to soda to about 5. The sodium silicate may be diluted to any degree desired for a particular application, particularly to contain about 20-30 weight % solids. For example, a sodium silicate comprising 37.5 weight % solids may be diluted with water (about 75 weight %) to a form a solution having approximately 25 weight % solids.

[0068] Another exemplary low-emission binder composition useful in the present application includes monoaluminum phosphate ("MAP"), which is a chemical prepared by reacting phosphoric acid (H₃P0₄) with aluminum oxide (A1₂0₃). This is an acid-base reaction and involves 3 moles of phosphoric acid per mole of Al . In the case of A1₂0₃, this works out to 6 moles of phosphoric acid per mole of A1₂0₃. In some exemplary embodiments, when the binder is in powder form, the composition comprises approximately 15-20% A1₂0₃ and 63- 67% H₃P0₄. In some exemplary embodiments, setting agents may be included, such as an alkali or alkali earth metal oxide component, such as sodium, magnesia, calcium, and combinations thereof. Such formulations offer interesting mechanical and chemical properties. The final ratio of oxides in the binder formulation may range from 0-15 weight % MgO, A1₂0₃, CaO, with the remainder being comprised of P₂0₅. In some exemplary embodiments, the binders prepared were aqueous solutions with solids contents ranging from 5% to 30%. The alteration of the base composition of MAP (4.18 P₂0₅: A1₂0₃ ratio) by the addition of MgO and CaO was found to yield less corrosive binder solutions.

[0069] The MAP may be diluted to any degree desired for a particular application, particularly to contain about 20-30 weight % solids. For example, 50 weight % solids MAP may be diluted with water (about 75 weight %) to a form a solution having approximately 25 weight % solids. [0070] In some exemplary embodiments, the low-emission binder composition is applied to the glass fibers to achieve a total binder content of about 1 to about 20 %, and particularly of about 2 to about 10%. Additionally, the binder composition may include a solids content of about 0 to about 100% and depends on the particular binder material used. For example, a poly(siloxane) binder may be used in a total binder content of about 4-10%, with 100% solids. For sodium silicate and MAP-based binders, the total binder content may be about 4- 10%, with solids ranging from 10% -50%.

[0071] It is a particular advantage that the low-emission binder composition not only meets the low-emissions standards set forth above, but additionally maintains, if not improves, the mechanical, thermal, and acoustic properties of traditional phenolic-based binder materials. The low-emission binder composition may further provide the advantage of limiting the dust formed during handling and loose filaments on preform surfaces, as compared to traditional phenolic-based binders.

[0072] The low-emission binder composition may be applied to the glass fibers in any form desired to conform to a particular process, such as, for example, as a solution or, alternatively, as a powder. According to some exemplary embodiments, the low-emission binder composition is applied to the glass fibers in the form of a solution. The low-emission binder composition solution may comprise an aqueous solution, such as a sodium silicate solution, or alternatively, in the case of The polymer mixture and cross-linking solution may preferably be mixed prior to poly(siloxane) for example, as a polymer mixture mixed with a cross-linking solution, such as a catalyst solution, application to the fibers.

[0073] Once the preform is formed with the glass fibers coated with the low-emission binder composition, the preform may then be cured by any desired method, such as by directing hot air through the apertures of the outer mold portion and/or the apertures of the inner mold portion. Alternatively, the mold may be placed in an oven and heated by radiation, convection, or a combination thereof. High-pressure steam may also be used as the source of heat to cure the binder. Upon curing, the low-emission binder composition generally forms cross-linked products through irreversible cross-linking reactions. In some exemplary embodiments, the preforms are cured at temperatures ranging from about 150 °C- 700 °C. The length of time the preforms are cured depend on the type of curing being used. For example, when curing the preform with hot air, the curing process may take anywhere from 2 minutes to 2 hours. In contrast, if steam curing, the cure time may be about 1-5 minutes.

[0074] Once cured, the lid (if present) may be removed, the outer mold portion 20 may be pivotally opened at the hinge 34, and the preform 18 may be removed from about the inner mold portion 22 (See, Figure 7). The preform 18 may then be inserted into the cavity of a muffler shell.

[0075] As binder compositions used in muffler preforms are exposed to high temperatures, they begin to decompose and may emit emissions, such as volatile organic compounds (VOCs) and other air pollutants during their decomposition. Such binder decomposition may be illustrated by the mass loss a binder undergoes upon heating to temperatures up to 1000 °C. A higher mass retention percentage indicates a more thermally stable binder composition and thus, less likely to emit gaseous species related to the degradation of the binder. Conventional phenolic resin binders undergo considerable mass loss upon heating and retain less than 5 %, or about 2 % of mass. In some exemplary embodiments, the low-emission binder composition has a mass retention of at least 60 weight %, or at least 70 weight %. In some exemplary embodiments, the low-emission binder composition has a mass retention of at least 80 weight %, or about 88 weight %.

[0076] Having generally introduced the general inventive concepts by disclosing various exemplary embodiments thereof, a further understanding can be obtained by reference to certain specific examples illustrated below which are provided for purposes of illustration only and are not intended to be all inclusive or otherwise limiting of the general inventive concepts.

EXAMPLES

[0077] In order to more thoroughly describe this invention, the following working examples are provided.

Example 1. Emission Testing

[0078] The following examples provide emission performance testing for various exemplary low-emission binder compositions described herein.

Example 1.1 : Thermal Performance of Polv(siloxane) Binder Compositions

A. Emissions Testing

[0079] Poly(siloxane)-based binder compositions were heated from room temperature to 180 °C in two different atmospheres, nitrogen with zero oxygen and air. The compositions were analyzed by tube furnace/infrared spectroscopy. Approximately 10 to 20 mg of the compositions were heated in the tube furnace from room temperature to 180 °C in nitrogen and zero air, temperature being ramped up ballistically. The flow rate was 100 ml/minute. Table 1 below lists the estimated amounts of identified components emitted. As demonstrated in Table 1, the poly(siloxane) binder compositions emit less than 20 mg/g total hydrocarbons. Table 1. Tube Furnace/Infrared Results for poly(siloxane) (results in mg/g of the sample)

B. Mass Loss

[0080] The compositions were then analyzed by thermalgravimetric analysis ("TGA") and the resulting thermogram is displayed in Figure 8. Figure 8 graphically displays a plot of the weight of a poly(siloxane) sample vs. temperature. The samples were heated to 800 °C and the mass was measured with the heat change, and averaged. The mass loss correlates with the emissions released from the binder material. The exemplary TGA of poly(siloxane) under air shows that there is a 10% mass loss related to curing where the temperature of the binder reaches up to 300 °C. Once the binder is cured, it is stable even when exposed to additional heat and only lost an additional 4% by mass due to combustion, between 400 °C and 600 °C. Considering that binders are typically applied in the 3-10% range, the effective loss of mass is very low.

[0081] Additionally, Figures 9(a) and (b) graphically display the TGA of poly(siloxane) binder that had been previously cured at 180 °C. The sample was subjected to a ramp rate of 20 °C/minute to 1000 °C under air (Figure 9(a)) and nitrogen (Figure 9(b)). Figures 9(a) and (b) illustrate that a cured poly(siloxane) binder undergoes a total mass loss of 12% as it is heated to 850 °C. Therefore, if a preform using poly(siloxane) requires 4% binder, this corresponds to a calculated loss on ignition of 0.6%.

[0082] In contrast, Figures 10(a) and (b) graphically display the weight % loss vs. temperature of a phenolic resin binder composition. Between the temperature range of 400 to 600 °C, a 24.931 mg phenolic resin sample experienced a weight reduction of about 91.40%. Additionally, between the same temperature range, a 30.1220 mg sample experienced a weight reduction of about 51.07%. The large weight loss that occurs indicates that the samples are releasing a significant amount of gaseous emissions into the atmosphere at typical working ranges (about 400-600 °C).

[0083] Example 1.2: Thermal Performance of Pre-cured Polvfsiloxane Binder Compositions

[0084] Exemplary binder compositions were prepared and tested for emissions: 1) poly(siloxane) cured at 70 °C, 2) poly(siloxane) cured at 180 °C. The cured binder compositions were then heated from room temperature to 450 °C in two different atmospheres (nitrogen and nitrogen with 1% oxygen). Tube furnace/infrared spectroscopy was employed to analyze the samples for emissions. Approximately 10 to 20 mg of each binder composition was heated in the tube furnace, with the temperature being ramped up ballistically

[0085] Table 2 summarizes the results in mg/g for the samples using the tube furnace/infrared spectroscopy technique. As shown below, the sample of poly(siloxane) cured at 180 °C emitted less than the poly(siloxane) cured at 70 °C. The estimated amount of water and carbon dioxide are listed in the table below. As compared to the results listed in Table 1, it is clear that the atmosphere of testing has an effect on the binder emissions. Table 2 represents oxygen-poor atmospheres, which mimic the atmospheres a muffler will experience in use.

Table 2: Tube Furnace/IR Emission Results for Poly(siloxane) (in mg/g of the sample)

[0086] The samples were additionally analyzed by a Frontier pyrolysis unit coupled to a gas chromatogram with mass spectroscopic detection. No compounds were emitted from the column. Example 1.3: Thermal Performance of Mono-aluminum Phosphate and Magnesium Oxide/Magnesium Phosphate Binders

[0087] Samples of exemplary binder compositions were prepared and tested for emissions: 1) mono-aluminum phosphate ("MAP") binder and 2) magnesium oxide/magnesium phosphate binder. The samples were heated from room temperature to 450 °C in two different atmospheres (nitrogen and nitrogen with 1% oxygen). Tube furnace/infrared spectroscopy was employed to analyze the samples for emissions. Approximately 10 to 20 mg of sample was heated in the tube furnace, with the temperature being ramped up ballistically. The flow rate was 100 ml/minute.

[0088] Table 3 summarizes the results in mg/g for the exemplary binder compositions using the tube furnace/infrared spectroscopy technique. Only water and carbon dioxide were emitted when each of the aluminum phosphate and magnesium oxide/magnesium phosphate samples were heated to 450 °C.

Table 3: Tube Furnace/Infrared Results for MAP and MgO MgP0₄ Binders (mg g)

Example 1.4: Comparative Example-Phenolic Binder Emissions

[0089] A phenolic binder composition was prepared and tested for emissions. The binder composition was heated from room temperature to 450 °C in two different atmospheres (nitrogen and nitrogen with 1% oxygen). The phenolic binder sample was analyzed both "as is" and after a pre-cure. Tube furnace/infrared spectroscopy was employed to analyze the samples for emissions. Approximately 10 to 100 mg of the samples was heated in the tube furnace, with the temperature being ramped up ballistically. The flow rate was 100 ml/minute.

[0090] Table 4 summarizes the results in mg/g for the phenolic resin sample using the tube furnace/infrared spectroscopy technique. Hexamethylene tetramine was detected in the phenolic binder sample that was not pre-cured. A trace of methane was also detected.

[Please comment on the high emissions detected. How high is this above the accepted limits?]

Table 4: Tube Furnace/Infrared Results for Phenolic Binder Atmos. Temp. Ammonia CO Total Hydrocarbon

As received N₂ 450 12.8 0.9 78.82

Pre-cured N₂ 450 5.6 0.9 78.62

Pre-cured N₂ 450 5.4 0.5 67.92

Pre-cured 1% 0₂ 450 4.6 2.5 45.82

Pre-cured 1% 0₂ 450 4.5 3.2 50.02

Example 2. Particulate Matter

[0091] Dust tests were performed on exemplary samples comprising texturized glass and a variety of binder compositions, including MAP, sodium silicate, colloidal alumina, colloidal silica, poly(siloxane), and phenolic resin, for comparison purposes. Dust tests are performed using an air sampler to generate a high flow rate of air over the sample. An exemplary dust testing air sampler is illustrated in Figures 11 (a)-(d). A cotton filter is placed in an air sampler test fixture and the test fixture is assembled by screwing a plastic sample holder into place as shown in Figure 11(c). A sample is then placed into the sample holder, as shown in Figure 11(d) and the test fixture was turned on, causing the plastic sample holder to spin for about three minutes. After the three minutes passed, the test fixture was stopped and the filter paper was removed and weighed to determine the weight gain due to collection of dust. As illustrated in Figure 12, samples prepared using MAP, sodium silicate, and poly(siloxane) as binders were found to be at least comparable, and often less dusty than phenolic resin sample. These results are further illustrated in the graph of Figure 13.

Example 3. Mechanical Properties

3.1 : Comparative Compression Testing

[0092] Mechanical tests were performed on samples comprising a phenolic binder (comparative) and exemplary binder compositions including sodium silicate, potassium silicate, poly(siloxane), aluminum phosphate, and chemically bonded ceramic, as illustrated in Figure 14. The binders that included solids, phenolic resin and chemically bonded phosphate-based ceramic were prepared by texturizing the glass, followed by mixing in the solids or slurry manually. Samples that utilized a liquid binder were prepared by feeding a binder into a texturizing nozzle as the glass is texturized. The glass fibers were then fed into a mold and cured at temperatures ranging from room temperature to 250 °C, depending on the binder used. The test data illustrated in Figure 14 was determined by subjecting the samples to a known weight and recoding the resultant deformation. As illustrated in Figure 14, aluminum phosphate, poly(siloxane), chemically bonded phosphate-based ceramic, potassium silicate and sodium silicate each exhibited low compressibility at binder contents in a desirable range, which is less than 20 %. The poly(siloxane) binder demonstrated a compressibility of about 10 %, which is comparable to conventional phenolic binders.

Example 3.2- Dimensional Stability of Poly(siloxane) Binder.

[0093] The dimensional stability of poly(siloxane)-based low-emission binder composition samples was determined via compression testing. The compression testing included preparing poly(siloxane) binder compositions using 99% siloxane oligomers and 1% Platinum as a catalyst. The binder composition was cured at 180 °C for 2 hours in a hot air oven and the binder composition was then loaded onto glass fibers. The binder-coated glass fibers were then packed into a container and the container was compressed.

[0094] As shown in Figure 15, at high binder content levels, such as above about 16%, the preforms illustrated a lower compressibility of about 2-7%. In contrast, when the binder content level was low, such as around 7-8%, the compressibility of the preform is increased to about 9-13%.

Example 4. Acoustics: Impedance and Absorption Testing per ASTM E1050-10

[0095] Twelve exemplary low-emission binder composition samples were prepared by weighing out each specimen to achieve a desired glass density (not including binder) of 120 g/1 at a test thickness of 1.25" within a 100 mm diameter tube, and inserting the fibers into a tube. A 100 mm diameter section of ¼" mesh galvanized hardware cloth was then placed in the open end of the tube to contain the inserted fibers (see Figure 16). For ASTM El 050 testing, the test method conformed exactly with the requirements of the method using a tube, two microphones, and a digital frequency analysis system. The results for each sample are illustrated in Figure 17.

[0096] As illustrated in Figure 17, each of the exemplary low-emission binder compositions, poly(siloxane), sodium silicate, potassium silicate, and MAP performed relatively comparable to the phenolic binder. As further illustrated, the poly(siloxane) binder sample demonstrated improved sound absorption compared to the phenolic binder sample. In general, each exemplary low-emission binder composition demonstrated the potential to provide a performance level comparable to existing phenolic-based binder products. [0097] The general inventive concepts have been described above both generically and with regard to various exemplary embodiments. Although the general inventive concepts have been set forth in what is believed to be exemplary illustrative embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure.

[0098] It will be understood that various changes may be made without departing from the scope of the invention, which is not to be considered limited to what is described in the description. While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the invention to such details. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the inventive concept, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.

[0099] While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions—such as alternative materials, configurations, methods, devices and components, alternatives as to form, fit and function, and so on—may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein.

[00100] Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated. The general inventive concepts are not otherwise limited, except for the recitation of the claims set forth below.

Claims

CLAIMS:

1. A low-emission binder composition for use in a glass fiber muffler preform, wherein said binder composition comprises a predominantly inorganic material, said low-emission binder composition has an LOI of no greater than 1.0 percent.

2. The low-emission binder composition of claim 1, wherein said predominantly inorganic material comprises one or more of clay; hydraulic cement; pure sulfoaluminate; a colloid; silicate; phosphate; chemically bonded phosphate-based ceramic (non-hydraulic ceramic), poly(propylene carbonate); polymeric silicone; and poly(siloxane).

3. The low-emission binder composition of any of claims 1 or 2, wherein said predominantly inorganic material includes one or more of sodium silicate, monoaluminum phosphate, and poly(siloxane).

4. The low-emission binder composition of any of claims 1 to 3, wherein said binder composition further includes a cross-linking agent.

5. The low-emission binder composition of claim 4, wherein said cross-linking agent is at least one of a platinum or peroxide solution.

6. The low-emission binder composition of any of claims 1 to 5, wherein said binder composition comprises at least 90 weight % of said predominantly inorganic organic material and at least 10 weight % of said cross-linking agent.

7. The low-emission binder composition of any of claims 1 to 6, wherein said binder composition comprises at least 99.5 weight % of said predominantly inorganic material and at least 0.5 weight % of said cross-linking agent.

8. The low-emission binder composition of any of claims 1 to 7, wherein said binder composition further includes one or more of a surfactant, clay, starch, acid, and latex.

9. The low-emission binder composition of any of claims 1 to 8, wherein said binder composition further includes a setting agent.

10. The low-emission binder composition of any of claims 1 to 9, wherein said binder composition is a solution.

11. A method for forming a preform product comprising:

applying a low-emission binder composition to a plurality of fibers;

filling a mold cavity with the binder-coated fibers; and

curing said fibers at a temperature between about 150 °C - 500 °C, wherein said low- emission binder composition has an LOI of no greater than 1.0 percent.

12. The method of claim 1 1 , further including the step of texturizing said fibers.

13. The method of claim 12, wherein said fibers are texturized and coated with said binder composition in a single continuous step.

14. The method of any of claims 11 to 13, wherein said fibers are continuous glass fibers.

15. The method any of claims 11 to 14, wherein the binder is applied to the fibers to achieve a total binder content of about 1 to 20 weight %.

16. The method of any of claims 11 to 15, wherein said low-emission binder composition comprises a predominantly inorganic material.

17. The method of any of claims 11 to 16, wherein said predominantly inorganic material comprises one or more of clay; hydraulic cement; pure sulfoaluminate; colloids; silicates; phosphates; chemically bonded phosphate-based ceramics (non-hydraulic ceramic), poly(propylene carbonate); polymeric silicones; and poly(siloxanes).

18. The method of any of claims 1 1 to 17, wherein said binder composition further includes a cross-linking agent.

19. The method of any of claims 11 to 18, wherein said cross-linking agent is at least one of a platinum or peroxide solution.

20. The method of any of claims 11 to 19, wherein said binder composition comprises at least 90 weight % of said predominantly organic material and at least 10 weight % of said cross-linking agent.

21. A preform product formed according to the method set forth in any of claims 1 1 to 20.

22. The preform product of claim 21, wherein said preform has mechanical and acoustic properties comparable to preforms formed with phenolic-based binders.