CELLULOSE-BASED INSULATION AND METHODS OF MAKING THE SAME

Abstract

A method for making cellulose-based fire resistant insulation. The insulation includes a plurality of superstructures that establish voids in the insulation. The insulation may be blown in place while the superstructures maintain the void portion of the insulation. The insulation is made with fiber residuals, either alone or in combination with other cellulosic materials. The method of making the insulation includes the steps of treating the cellulosic materials with a fire retardancy chemical or chemicals and creating bonds between the fibers to form the superstructures.

Claims

1. A method for manufacturing fire resistant insulation using cellulosic fibers, the method comprising the steps of: cleaning the cellulosic fibers; partially dewatering the treated cellulosic fibers; treating the cleaned cellulosic fibers with fire retardant material; drying the treated cellulosic fibers; and forming a plurality of superstructures of at least a portion of the treated cellulosic fibers.

2. The method of claim 1 wherein at least a portion of the cellulosic fibers comes from SFR.

3. The method of claim 2 wherein the SFR is combined with recycled cellulose fiber.

4. The method of claim 1 wherein the fire retardant material includes one or more borate-based compounds, magnesium sulfate or a combination of these materials.

5. The method of claim 1 wherein the fire retardant material and the cellulosic fibers are combined together in a process where the fibers have a moisture content of between 20-99%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a simplified representation of an example system that can be used to make the cellulose-based insulation of the present invention.

[0035] FIG. 2 is a block diagram representation of primary steps of a process that can be used to make the cellulose insulation of the present invention.

[0036] FIG. 3 shows an example of a mechanism that can be used to make a textured mat for forming fibers into superstructures, with a compacted core and then several protruding fibers in multiple directions, using rollers with pressure points.

[0037] FIG. 4 shows how the protruding fibers of individual superstructures separate adjacent superstructures from one another.

[0038] FIG. 5 shows how the presence of superstructures as part of the insulation of the present invention can cause other individual fibers to drape over the superstructures, rather than settling into a compressed orientation.

[0039] FIG. 6 shows how individual fibers without superstructures present can settle into a more densely packed configuration in an insulation of the prior art without superstructures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] FIG. 1 illustrates a simplified representation of primary components of a system 10 used to make a cellulose-based insulation with fire retardancy of the present invention, which insulation is represented in FIG. 5. The insulation of the present invention includes superstructure constructs of the feedstock materials used to make it, which superstructures enhance the void features and, therefore, improving the thermal performance characteristics of the insulation. The insulation may be installed in place, such as by blowing or spraying it in place, while maintaining the integrity of the superstructures and thereby maintaining the void integrity of the insulation after installation. Primary steps of a process for making a cellulose-based insulation of the present invention are represented in FIG. 2.

[0041] The system 10 may be configured as shown in FIG. 1 and include a feedstock source container 12, a chemical treatment source 14, which may be a holding tank or any other source of additive, a blend tank 16, a dewatering unit 18, a drying unit 22, a superstructure formation unit 24, a fiberizing unit 26, a classifying unit 28, and a collection unit 30. The feedstock source container 12 is filled with cleaned feedstock material such as one or more of the cellulose-based recycled materials described herein. The feedstock may be moved manually or automatically into a dewatering unit 18 and then into the blend tank 16. It should be understood that the dewatering unit 18 may be located before or after the blend tank 16 where the fire retardant chemicals and other additives may be added. It is to be understood that the blend tank 16 is a representation of a structure within which the feedstock and any chemical additives of interest may be combined. Further, the blend tank 16 represents one or more such tanks within which feedstock and additives are combined. Heat may be applied in the blend tank to enhance the absorption of the fire retardant into the fibers.

[0042] The feedstock used to form the cellulose-based insulation of the present invention is a plurality of pieces including fibers but not limited thereto, of SFR or other fiber residuals. These materials may be processed alone, or may be interspersed with other materials, such as other recyclable cellulosic materials including, but not limited to, OCC and ONP, and added to the blend tank 16 containing desired additives, which may include water as noted.

[0043] The chemical treatment source 14 includes a liquid or suspension of treatment material, which may be a combination of a fire retardancy chemical water, and any other additives that may be of interest. The fire retardancy material may be in liquid form rather than powder form prior to delivery to the blend tank 16, but it should be understood that it may also be possible to add dry fire retardants directly into the blend tank 16, where they can be dissolved by the moisture present in the blend tank 16, thereby removing the need for a source tank 14 that includes additives in liquid form. The fire retardancy material may be a borate (such as boric acid, borax, or other borates), a combination of borates, magnesium sulfate, or a combination of one or more borates and magnesium sulfate. The use of magnesium sulfate reduces the overall cost of the insulation. Whereas prior uses of magnesium sulfate and/or borates as fire retardancy additive has been limited to application of such additives in powder form, the present invention in a liquid process, such as by adding that combination to the blend tank 16 either in liquid form or in powder form, for interaction with wet fibers improves the adhesion of that fire retardancy combination as compared to a dry mixing of the combination and the fibers. It is to be understood that other suitable fire retardancy chemicals may be employed. An aspect of the invention is that the fire retardancy chemical is combined with the feedstock in the presence of moisture levels in excess of 20% so as to provide effective penetration of the fire retardant into the fiber structure of the feedstock component from the feedstock source container 12.

[0044] Another additive of the chemical treatment source that may be of interest and used in the feedstock treatment process is a chemical, biological or other additive to eliminate or reduce one or more components of the feedstock that may result in a product with undesirable characteristics. For example, a cellulosic feedstock that is a recycled material may include one or more bonding agents comprising polysaccharides, starches and the like that, if carried through to the end product, may facilitate mold growth. An additive such as an enzyme or other component to break down such undesirable components, and/or make them sufficiently fluidized that they can be removed from the treated feedstock, may be added to the blend tank 16 as an aspect of the present invention.

[0045] Another additive of the chemical treatment source that may be of interest and used in the feedstock treatment process is an adhesive, resin, or a chemical, biological, or other additive designed to enhance the bonding between fibers, which may help to subsequently form or strengthen superstructures that may be formed during subsequent processing steps. These additives or treatments may also be added downstream of the blend tank, for example by being sprayed onto the material during or after the drying process.

[0046] The superstructure formation unit 24 may be positioned after the dryer in order to promote the formation of superstructures. These superstructures may be formed by any of the methods described above, through any means of gathering fibers together and then promotion the agglomeration of fibers together into superstructures that include fibers that are permanently adhered to one another. This may occur in combination with heat, pressure, or the addition of binding agents. It should also be noted the that formation of these bonds between fibers may also be effected within the blend tank or the drying step, so that a separate superstructure formation system may not be required.

[0047] The fiberizing unit 26 may be utilized to create a finer fiber structure. If superstructures have been formed that are larger than are desirable in the finished product, the fiberizer may be effective in limiting the size of such superstructures. In addition, if large particles have come through the process from prior steps, such as larger pieces of recycled paper, the fiberizer may also reduce the size of those materials, which may improve the density of the finished process.

[0048] It should also be understood that the formation of superstructures may also be accomplished after the fiberizing step, and not before, if that provides the optimal combination of fiber and superstructure geometry that is desired for a particular application. It should also be understood that an additive to promote binding of fibers into superstructures may be added upstream or downstream of the fiberizer. Finally, it should be understood that some portion of any feedstock stream may pass through a portion of the aforementioned steps, while another portion of the feedstock stream may bypass certain sections, with the critical aspect of this invention being that at least 5% of the materials are formed into superstructures as described above.

[0049] With reference to FIG. 2, the primary steps used in the process to make the insulation of the present invention are as follows. The process is summarized in the following primary steps that can be used to produce the insulation of the present invention: (a) obtaining and providing SFR feedstock materials, alone or in combination with other cellulosic materials, (b) cleaning the SFR feedstock materials (and any additional feedstock materials), (c) dewatering the treated feedstock materials, (d) treating the cleaned materials with fire retardant chemical additive and/or other additives, (c) drying the resultant materials, (f) creating bonds between fibers of the feedstock materials to form a plurality of superstructures, (g) fiberizing the dried materials including superstructures therein, (h) classifying the fiberized materials and (i) collecting and bagging the finished product. It should be understood that some of the steps may be adjusted or used in a different order. In addition, the cleaning step, for example, is not required in order to achieve the formation of the superstructures. Further, additional processing steps, such as fluffing the material prior to drying may be advantageous, if they promote the effectiveness of subsequent processing steps.

[0050] SFR feedstock materials may be obtained from pulping operations in an aqueous state and then may be dewatered to bring the moisture content of the material to approximately 25% to 75%.

[0051] The SFR and other feedstock materials may be treated with a fire retardant material in the blend tank 16 such as by utilizing an aqueous solution containing a blend of chemicals of the type described herein at an elevated temperature for an established dwell time, to allow the fire retardancy chemicals to saturate the feedstock material. The moisture of the SFR may also be sufficient at this stage to allow that dry chemicals are added to the blend tank, providing that there is sufficient moisture present to dissolve a substantial portion of the chemicals added to the blend tank, such that a substantial portion of the chemicals are infused into the fiber structure of the cellulose. This treatment may take place together with other feedstock materials as noted, the SFR may be treated separately from the other feedstocks, or only one of the feedstock streams may be treated with a fire retardant.

[0052] The SFR materials and other blended feedstock materials, if any, may be dewatered in the dewatering unit 18 using any means of technologies known to those of skill in the art, such as a press or a screen to separate the fibers from water. Aqueous solutions that are removed from the materials during the dewatering step may be reintroduced into a subsequent batch of product or reintroduced at the stage of aqueous treatment in a continuous process. This reuse of fluids is useful in making the overall process economical, as the fire retardant chemicals are far more expensive than the cellulosic fiber materials and would otherwise render the process uneconomical.

[0053] The treated and dewatered materials may be fluffed in the fluffing unit 20 before being transferred to the drying unit 22, or alternatively, a rotary or fluidized bed dryer as the drying unit 22 may be utilized which may be capable of fluffing the material while it is dried, thereby avoiding the need for a separate form of the fluffing unit 20.

[0054] The drying unit 22 may be utilized to drive remaining moisture out of the treated feedstock materials. For example, a rotary drier, a fluff dryer, air drying or any other conventional drying process may be utilized to separate the majority of the remaining moisture in the treated feedstock fibers.

[0055] During drying either in the drying unit 22 or in combination with the superstructure formation unit 24, the treated materials may be formed into a three-dimensional structure by a number of techniques. The materials may be dried on a conveyor to form a dry mat. The materials may be formed by rollers to form paper-like sheets or tubes. The rollers may be textured to provide specific qualities of the paper-like sheets, for example controlling the ratio of densified to undensified fibers. An example of such a roller configuration as an element of the superstructure formation unit 24 is shown in FIG. 3, in which nips 42 of rollers 40 pinch portions of groups of fibers 44 together while allowing others to remain spaced from one another and either dried or sized to remain of fixed superstructure configuration.

[0056] Alternatively, during or after drying, other materials may be added to the treated fibers in the superstructure formation unit 24, which may simply be a container, to promote bonding between the fibers. A sizing additive such as an adhesive may be used as a binding agent to bind fibers together into the three-dimensional superstructure. Similarly, a polymer spray may be applied to form links between fibers, that result in a strong three-dimensional matrix of fibers establishing the superstructures in random or organized form configured to establish fixed spacing between fibers of such clusters and thereby establish voids of the insulation. Finally, nanocellulose may be used to bind larger fibers together due to its extensive availability of sites and surface area for hydrogen bonding.

[0057] Following drying and superstructure formation, the treated materials may be fiberized in the fiberizing unit 26 to separate individual fibers as well as separating clusters of superstructures of fiber combinations. This may be accomplished utilizing a rotary fiberizer or disk refiner with plate gaps of various distances that are tuned to optimize the performance of the finished cellulose insulation.

[0058] Following fiberization, the materials may be classified using the fiber classifier 28, which may be a screening system or an air system or a combination of a screening and an air system. The purpose of such a classification is to separate high density materials, such as individual fibers packed relatively close together, from lower density materials, such as the clusters of superstructures of fiber groups, to control and make selectable based on combinations of such high and low density groups, the resultant overall bulk density of the insulation product to be installed in place, such as by blowing it in place. The use of a classifier allows the finished product to meet desired insulation requirements, even when utilizing a short fiber feedstock, such as SFR as well as other feedstock materials that may be used, cither alone or in combination with SFR. It should be understood that the use of a classifier may be advantageous in some instances, but may not be required for certain applications.

[0059] FIG. 4 shows a simplified representation of the way formed superstructures 50, when stacked together, produce pockets or voids 52 that remain fixed in place after collection and after the insulation formed therewith has been installed. In FIG. 4, each of the clusters of fibers represents a superstructure, with fibers of a particular cluster being permanently joined together to form the superstructure shown.

[0060] FIG. 5 shows a simplified representation of how the presence of superstructures can reduce the density of a blended material containing superstructures and individual fibers. In this illustration, all superstructures are shown as clusters of crossing straight heavy lines and individual fibers are shown as lighter curved solid lines. (It should be understood that this is for illustration purposes and all fibers may have straight or curved sections.) The presence of the superstructures has two effects: first, superstructures tend to fall on top of one another reducing the density of the resulting bulk material; and secondly, the individual fibers tend to drape over superstructures. This allows that the void fraction of the insulation of the present invention is at least 30%, with the superstructures contributing voids to the overall matrix and helping to separate other individual fibers that may not be permanently affixed to any superstructure.

[0061] FIG. 6 shows the problem of high density with short fibers using conventional insulation production methods in a prior art insulation that has no superstructures to maintain fixed voids. The fine fibers tend to fall into alignment and to stack more densely than when superstructures are present to separate the fibers.

[0062] Materials that may be purged out of the finished product stream during classification can be fed back into the process in upstream steps. For example, cellulose that was too dense for finished product may be reintroduced in advance of the matting step and may be usable when matted with other fibers in a second cycle. This reuse of materials after classification is doubly important in first allowing SFR to be usable as a feedstock and secondly in allowing the expensive fire retardants to be recovered in the process.

[0063] The resulting product may then be packaged for distribution using the collection unit 30.

[0064] In addition, it may be advantageous to combine the teachings from this disclosure with the teachings from prior patent grant U.S. Pat. No. 8,043,384, which teaches how to utilize a variety of feed stocks for manufacturing cellulose insulation. In that process, a feedstock may be utilized that incorporates a bonding agent, which may be present in old corrugated cardboard.

[0065] In applying the information of this disclosure, the SFR materials may be advantageously mixed with OCC, DLK, ONP, fluids and/or fiber materials recovered from other process stages or other materials at various steps in the process, which may include: [0066] a) Mixing the SFR materials with other materials prior to treatment with a fire retardant blend (for example between steps {a} and {b} above) [0067] b) Mixing the SFR materials with other materials after cleaning (between steps {b} and {c} above) [0068] c) Mixing the SFR materials with other materials after treatments (between steps {c} and {d} above). In this case, the SFR materials may be treated for a different amount of time or under different conditions than the other materials and may have a higher or lower content of fire retardant materials than the other materials. [0069] d) Mixing the SFR materials with other materials after any other subsequent stage of processing, providing that a mix of materials is ultimately provided in a bagging operation that includes the SFR materials and other materials. [0070] e) Mixing SFR materials that may be moist with other materials that may be dry, or vice versa, in order to allow the dryer of the two materials to wick moisture away from the wetter material, or to suppress dust that may be produced by the dryer material.

[0071] Finally, it may be advantageous to pursue an alternative process for the production of these materials that involves mixing the chemicals that provide fire retardancy into the SFR while the SFR and/or other feedstock materials is semi-dry, rather than mixing it into the slurry pulp (which is almost all water). In that case, alternative means of mixing may be utilized, such as a ribbon mixer.

[0072] The present invention of a method for providing an improved fire retardant material and a cellulose insulation having a plurality of superstructures thereof that can be blown in place have been described with respect to specific components and method steps. Nevertheless, it is to be understood that various modifications may be made without departing from the spirit and scope of the invention. In particular, it should be understood that any reference to the use of SFR as a feedstock could be equally well applied to other fiber residuals with similar properties from other sources. All equivalents are deemed to fall within the scope of this description of the invention as identified by the following claims.