Patent Application
20080197316
The present invention relates generally to mineral fiber insulation products and methods of making the same.
Batt insulation is commonly manufactured by fiberizing mineral fibers from a molten mineral bath (e.g., molten glass) by forcing them through a spinner rotating at a high number of revolutions per minute. The fine fibers are then contacted by a pressurized hot gas to draw the fibers to a useable diameter and length. The fibers are typically sprayed with an organic material, such as a phenol/formaldehyde binder. The fibers are then collected and distributed on a conveyor to form a mat. The resin is then cured in a curing oven. The mat is then sliced into lengthwise strips having desired widths and chopped into individual batts. In some cases, a facing material, such as Kraft paper coated with a bituminous material or other vapor retarder, is added to the mat prior to the cutting step.
Often, the organic material is provided in an aqueous solution and sprayed onto the cylindrical veils of rotary spun glass fibers. Typically, the phenol/formaldehyde binder contains urea, and has a molecular weight of around 600 in the uncured state in the aqueous solution being applied to the glass fibers.
One of the problems with applying aqueous organic binders to cylindrical veils of mineral fibers is that a portion of the binder tends to evaporate prior to contact between the liquid binder drop and a mineral fiber in the veil. This evaporated binder material becomes a contaminant in the exhaust air stream of the process and must be cleaned, adding significant expense to the manufacturing process. Further, the binder material on the mineral fibers tends to be sticky and necessitates extensive cleaning of the fiber collection apparatus in order to avoid the formation of product defects.
Another problem associated with the application of the thermosetting phenolic binder material is that a curing process is required. Typical problems associated with curing include operational costs associated with the curing oven, the cost of handling pollution issues, degree of cure problems and product integrity problems.
Aqueous-based formaldehyde-free binders have been proposed in the art. For example, acrylic binders that are formaldehyde-free have been proposed in place of the phenol/formaldehyde resin binders. Examples of formaldehyde-free binders used in such applications can be found in U.S. Pat. Nos. 5,932,665 and 6,331,350. However, because these acrylic binders are applied in aqueous form, they are difficult to use since a low PH is required for storage and application, at least when compared with binders in dry form.
U.S. Pat. No. 5,595,584 to Loftus et al. proposes an insulation manufacturing system that aligns centrifugal spinnerets for mineral fibers and organic fibers above a collection surface to form alternating mineral and organic fiber veils. The organic and mineral fibers commingle and accumulate on the collection surface. The collected fibers are then processed to form an insulation product. It is very difficult to obtain uniformly blended mats of glass and organic fibers using this system.
Finally, U.S. Pat. No. 5,983,586 to Berdan, II et al. discloses a fibrous insulation manufacturing system for forming a binderless, encapsulated insulation blanket. The binderless insulation blanket includes organic fibers and very long (about 1-3 meters in length) thermoplastic fibers. As with the system of the '584 patent, it is very difficult to obtain uniformly blended mats of glass and organic fibers using this system.
Improved methods of manufacturing a formaldehyde-free insulation product are desired. Improved insulation products are also desired.
A method of forming a fibrous insulation product includes forming at least one fibrous veil including first fibers and blowing a non-aqueous, formaldehyde-free, thermoplastic binder in powdered, liquid or fibrous form into the veil during said forming step to form a mixture of the binder and the first fibers. When in fibrous form, the binder fibers have average length of less than or equal to about 15 mm. The mixture is collected on the forming belt and formed into an insulation batt, board or molding media.
A system for forming a fibrous insulation product is also provided. The system includes at least one fiberizing apparatus for forming a fibrous veil comprising first fibers and means for blowing a non-aqueous, formaldehyde-free, thermoplastic binder in powder, liquid or fibrous form into the veil to form a mixture of the binder and the first fibers, the fibrous form having average length of less than or equal to about 15 mm. A forming belt is disposed below the fiberizing apparatus for collecting the mixture. The system also includes an oven for heating the mixture to a temperature at or above the melting temperature of the thermoplastic binder.
The manufacturing system and method avoids or substantially reduces contamination and other problems associated with phenolic resins by using a non-aqueous, formaldehyde-free thermoplastic polymer binder to bind the insulation fibers. Use of a non-aqueous solution lessens the storage area needed for the binder and generally provides a simpler, cleaner, more efficient process. Further, the final insulation product is formaldehyde-free, or substantially free.
In one particular embodiment of a method of forming an insulation product, a non-aqueous, formaldehyde-free, thermoplastic binder is directed from a hot melt applicator into the fibrous veil to form a mixture of the binder and the first fibers. The mixture is heated to a temperature above the melting temperature of the thermoplastic binder in an oven, wherein at least a majority of the thermoplastic binder is melted, whereby the melted thermoplastic binder forms meltbonds with the first fibers when cooled.
In one embodiment, the thermoplastic binder is provided as a powder, which is formed using a gas atomization process.
The above and other features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention that is provided in connection with the accompanying drawings.
The accompanying drawings illustrate preferred embodiments of the invention, as well as other information pertinent to the disclosure, in which:
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
In embodiments, the veil 106 can be formed using a veil forming process as described in, for example, WO 2002/070417 entitled “Process and Device for Formation of Mineral Wool Products,” the entirety of which is incorporated by reference herein. The process described therein is known as “internal centrifugation.”
Nozzles (not shown) can optionally be positioned to direct liquid sprays into the veil 106. Such sprays could include water or other evaporative liquid to cool the fibers and associated gases within the veil 106. The nozzles could also spray a lubricant onto the fibers to reduce fiber-to-fiber friction in the ultimate insulation product, which could thereby prevent fiber damage.
Another common device (not shown) for affecting the veil 106 is a set of air lappers that are positioned on either side of the veil 106. The air lappers discharge air to sweep or direct the veil 106 from side to side of the forming hood 122 (shown in
Pneumatic pressure, i.e., air, can be provided from source 136a to attenuate thermoplastic binder fibers extruded from die 134a and to blow the fibers into the veil 106. Hydraulic pressure can be provided from source 136a to provide drive pressure in gun 132a for pushing the melted polymer through die/nozzle head 134a. This pressure may also be supplied by an electrically driven pressure means, as opposed to pneumatically.
Window A of
Melt blown applicator 130b is similar to melt blown applicator 130a, in that it includes a gun 132b, a pneumatic or hydraulic source (not shown) and a thermoplastic polymer melter (also not shown). Unlike melt blown applicator 130a, however, the melt blown applicator 130b is configured, such as by a selected die or nozzle 134b, to provide the thermoplastic binder in droplet rather than fibrous form. The applicator 130b blows droplets 190 into veil 106 to coat the rotary fibers 150, as best seen in enlarged window B. As can be seen in window B, the droplets 190 can form melt bonds 170 with the rotary fibers 170 or simply coat or partially coat the fibers.
In an exemplary embodiment, the hot melt applicators 130a and 130b use the Nordson ProBlue® hot melt unit available from Nordson Corporation of Westlake, Ohio as polymer melter 138a. These melters have tank capacities up to 50 liters. This device melts the thermoplastic polymer and pumps the melted polymer to hot melt gun 132a. Appropriate applicators can be selected for die 134a and gun 132a in order to form the melted polymer into fibers 160 and/or droplets 190. One exemplary Nordson applicator is the Nordson Series MB-200 Meltblown Applicator which utilizes air jets to create blown fibers ranging in size from 0.2-50 μm in diameter and shorter than 200 mm in length. Various dies and number of dies can be attached to the MB-200 Meltblown Applicator to adjust fiber size and coverage. Another exemplary applicator is the Nordson MELTEX® Series EP 11 Slot Gun applicator, which has an application width of 400 mm or more. Still further, another exemplary applicator is the Nordson CONTROL COAT® System applicator, which produces fine fibers by impinging heated air on the hot melt as it is extruded through slot openings to stretch and shred the blown adhesive.
Exemplary nozzles for die 134a include Nordson UNIVERAL™ CF® (Controlled Fiberization) nozzles, Nordson EP nozzles, and Nordson UNIVERSAL™ SUMMIT™ nozzles. The same nozzles can be used for applicator 134b by adjusting the temperature and pressure, flow rate and/or other process parameters to form droplets 190.
The diameter and length of the thermoplastic polymer fibers 160 and the diameter of the thermoplastic droplets 190 may be controlled by several process parameters, including polymer temperature, fluid pressure, atomizing air pressure, fluid flow rate, and nozzle orifice size. The choice of the polymer and its melt index may also affect the fiber and particle size.
In one embodiment, the thermoplastic binder fibers 160 have average diameters between about 0.2 to about 20 μm, and more preferably between about 0.5 to about 15 μm. These fibers have average lengths between about 0.1 to about 15 mm, and more preferably between about 0.1 to about 6 mm.
In one embodiment, the thermoplastic binder droplets 190 have average diameters between about 0.5 to about 10 μm, and more preferably between about 0.5 to about 6 μm.
An opening 123a can be provided in the wall of a closed forming hood 122 through which melt blown applicator 130a blows fibers 160 into veil 106. It will be understood that no opening is needed in an open forming hood. Alternatively, part or all of the applicator 130a could be disposed within the hood 122. Likewise, an opening 123b is provided in the wall of forming hood 122 through which melt blown applicator 130b blows droplets 190 into veil 106. Alternatively, part or all of the applicator 130b could be disposed within the hood 122. In exemplary embodiments, a sufficient number of applicators 130a and/or 130b are provided around the circumference of the veil 106, such as at spaced increments, so as to provide a substantially homogenous mix of fibers 160 and thermoplastic polymer binder in mixture or pack 104. The melt blown applicators may be positioned such that they are in an approximately 15-45° angle, and more preferably a 30° angle from the horizontal plane in order to blow into the veil 106 at a downward angle towards the forming belt 102. In one embodiment, the applicators 130a and/or 130b are disposed between about 100-200 mm, and more preferably about 150 mm, laterally away from the veil. In one embodiment, the applicators are positioned so that the blown fibers or droplets intersect the veil 106 at about 500-700 mm, and preferably at about 600 mm, from the spinneret (i.e., from the beginning of the veil 106).
In exemplary embodiments, the pack 104, and thus the ultimate insulation product, includes between about 1-20% by weight of thermoplastic binder, and more preferably between about 3-15% by weight of thermoplastic binder. Preferred embodiments use no phenolic resin binder, though in some applications small amounts, such as 1-5% by weight phenolic resin binder, may be incorporated into the product using conventional methods of application.
In one embodiment, the apparatus 210 includes a chamber 212 for storage of the thermoplastic binder in powdered form. The binder particles 200 can be blown from the chamber 212 using air source (e.g., a blower) 216 through pipe or other conduit 214 into the forming hood 122 to veil 106. In one embodiment, the powdered binder particles are ground from a source material using grinding techniques familiar to those in the art to a size of less than or equal to about 100 μm, and stored in bulk in chamber 212. In an alternative embodiment, the powdered binder can be provided from what is known as a gas atomizer. A gas atomizer 218 is shown coupled directly to chamber 212, though there is no reason the gas atomizer 218 could not simply be used to produce powdered binder particles that are later supplied to chamber 212.
Gas atomizers are described in, for example, U.S. Pat. Nos. 6,171,433, 6,461,546 and 6,533,563, the entirety of each of which is hereby incorporated by reference herein. In one embodiment, the gas atomizer 218 includes a high pressure crucible where the thermoplastic polymer is heated under inert atmosphere and under high pressure until molten. The molten polymer is forced under pressure through a pour tube and into an atomization nozzle. The polymer is then atomized in an atomization chamber and molten droplets of polymer fall through the atomization chamber. As the droplets fall, they cool to form the polymer powder. The polymer powder is then collected in a collection chamber, such as chamber 212 or separate chamber for transport to chamber 212. Various shapes and sizes of particle can be formed. In one embodiment, the gas atomizer forms uniform micron-sized spherical particles. The gas atomizer can form spherical particle sizes ranging from close to 0 μm to about 250 μm. In embodiments, the particles 200 have average diameters between about 0.2 to about 60 μm, and more preferably between about 2 to about 30 μm. The gas atomizer can also be configured to form elongated spheres or whisker particles. Whisker particles formed by the gas atomizer have diameters of about 100 nm and lengths of a few millimeters. An exemplary material for use in the gas atomizer 218 is polyethylene.
In preferred embodiments, the rotary fibers 160 are mineral fibers, such as glass fibers, though other fibers, such as rock wool fibers, polymer fibers or other insulation fibers may also be utilized. In one embodiment, the average fiber diameter is between about 0.25 to 8 μm, and preferably between about 1 to 6 μm. The preferred average length of the fibers is between about 1 to 100 mm, and more preferably between about 5 to 75 mm.
As shown in
The pack 106 is preferably heated to a temperature and for a period of time such that at least a majority, and preferably substantially all, of the polymeric binder therein melts, particularly when the polymeric binder is the only binder present in the pack 106. Preferably, between about 50-100% of the thermoplastic binder is completely melted, and more preferably about 80-100%. Put another way, preferably between about 50-100%, and more preferably between about 80-100%, of the added thermoplastic binder is melted so that the binder flows to form melt bonds between fibers 150 once cooled.
Exemplary thermoplastic polymers for use as the thermoplastic binder include inonomer, ethylene methyl acrylate, ethylene acrylic acid, polyacetal (Acetal), polybutylene terephthalate (PBT), polyphthalate carbonate, polyethylene terephthalate (PET), polylactic acid, styrene acrylonitrile, acrylonitrile styrene acrylate, polyethersulfone, polystyrene, polyethylene, polypropylene, ethylene vinyl acetate, nylon, polyester, polyvinyl chloride, ethylene vinyl alcohol, polycarbonate, acrylonitrile butadiene styrene (ABS), polyoxymethylene, polyoxymethyl methacrylate, or a blend of two or more of these materials. The following table lists some exemplary commercially available thermoplastic polymers that may be used as the thermoplastic binder described above. The temperature inside the oven 302 is determined by the melting temperature of the selected material and the amount of time it takes for the pack to pass through the oven 302.
Immediately following the oven 302 is a cooling section 304 where the fibrous product is cooled with ambient air that passes through the insulation through the use of a suction chamber below the mat. Cooled fibrous lane 306 exits the cooling section 304. The fibrous lane 306 optionally can be passed through facing layer applicator 308 which takes a facing layer, such as a thin film of polyethylene or kraft material, from a roll 309 and applies the film to the insulation lane 306, such as with an adhesive or bituminous layer. Alternatively, the fibrous lane 306 can be encapsulated in a material or left uncovered. Subsequently, the insulation lane 306 is cut into lengths by the chopper 312 to form batt products 314, board products or roll products. The product can be rolled by a roll-up machine at the end of the insulation production line.
The rolls, batts, or board products may subsequently be used as a molding media where they are compressed and shaped with heat and pressure above the melting point of the thermoplastic binder and then cooled below that melting point to permit them to maintain the shape of the mold. By “molding media” it is meant an insulation mat that can be subsequently compressed and reshaped in a heated molding process to manufacture a dense flat board or a contoured insulation that is used as, for example, insulation in automobiles. A reshaped product can be referred to as a “molded media.”
The batts (boards or molding media) 314 are preferably in a density range of about 0.35-8 lb/ft3 (4.8-128 kg/m3), and preferably about 0.3-6 lb/ft3 (4.8-96 kg/m3), and still more preferably about 0.4 to 4.0 lb/ft3 (6.4-64 kg/m3). The thickness of the insulation layer is generally proportional to the insulated effectiveness or “R-value” of the insulation. Low density batts may typically have a density between 0.3 and 2 lb/ft3 and a thickness between 2 and 12 inches. Boards may typically have a density between 1 and 8 lb/ft3 and a thickness between 0.25 and 6 inches and may be produced as sheets about 2 to 4 feet wide by about 4 to 12 feet long. Molding media may typically have a density between 0.3 and 2 lbs/ft3 and a thickness between 1 and 4 inches and may be produced in rolls about 2 to 8 feet wide and 50 to 200 feet long.
Though low density batts are preferred candidates, as explained above the present disclosure also applies to higher density semi-rigid and rigid insulation boards (“high density” insulation) and molding media. It should be understood that the insulation batt, board or molding media can provide thermal and/or acoustic insulation properties.
The manufacturing system described herein avoids or substantially reduces contamination and other problems associated with phenolic resins by using a non-aqueous, formaldehyde-free thermoplastic polymer binder to bind the insulation fibers. Use of a non-aqueous solution lessens the storage area needed for the binder and generally provides a cleaner, more efficient process. The final insulation product is formaldehyde-free, or substantially free.
Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention that may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
