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Mineral fiber insulation having thermoplastic polymer binder and method of making the same

Mineral fiber insulation having thermoplastic polymer binder and method of making the same description/claims

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:

• Provisional Patent
• Utility Patent

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