Patent Publication Number: US-2020277782-A1

Title: Fire-retardant for an insulation product

Description:
RELATED APPLICATIONS 
     The present application is a United States National Stage Application of International Patent Application No. PCT/US2018/060755, filed on Nov. 13, 2018, which claims priority to U.S. patent application Ser. No. 15/816,482 by Branislav R. Simonovic and titled “Fire-Retardant for an Insulation Product,” which was filed 17 Nov. 2017, the disclosure of which is incorporated herein by this reference. 
    
    
     FIELD 
     The present invention relates to an insulating materials processed with a fire-retardant or fire suppressant chemical. The insulation product may include other materials, such as anti-fungal and anti-bacterial chemicals and corrosion inhibitors, among others. 
     BACKGROUND 
     This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This description is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art. 
     Using cellulose as insulation was first patented in England in 1893. In the United States, the application of cellulose insulation dates from 1920&#39;s, but such insulation was extensively used from the mid-1970s. Since cellulose insulation (CI) is based on recycled paper and cardboard, CI is well recognized as an energy efficient, green product. The addition of flame-retardant chemicals makes the CI more fire-resistant. The primary consumer of CI is the building industry, which has about 10-15% of the residential market. CI is used as thermal insulation and an acoustic barrier. 
     CI production is performed by shredding recycled paper, such as newsprint, mixed paper, cardboard and the like, and applying additives to improve the resistance of cellulose fibers to ignition at high temperatures. The additives may include different flame-retardant and flame suppressant chemicals. The most common chemicals that have been used include boric acid, borax, and ammonium sulfate. Further chemicals have included gypsum, sodium hydroxide, sodium sulfide, formaldehyde, some resins, gums, or talc, and the like. The fire-retardant chemicals, or mixtures, may be added to cellulosic fibers as solid powder, or by spraying liquid solutions of fire-retardant chemicals. 
     Estimated consumption of three common chemicals used as fire-retardants during peak production of CI in the mid-1970&#39;s, was 45,300 tons of boric acid, 18,300 tons of boron, and 58,000 tons of boric oxide. According to the European Commission (EC) Regulation No. 1272/2008 amended by Commission Regulation (EC) No. 790/2009, boric acid, boric oxide and specific sodium borate salts, including borax, were classified as toxic chemicals, because of potential reproductive toxicity. When these substances are present in preparations or mixtures, specific concentration limits apply before the preparation is classified in this way. For boric acid this limit is 5.5%, which means that only those preparations containing 5.5% or more of free boric acid have to be classified in this way. 
     Beside the boron and boron compounds, ammonium sulfate is the most usable chemical in CI production. After 2011, compounds have been substituted for boric acid due to the classification as a reproductive toxicant. For example, manufacturers have replaced the boron salts with flame retardants containing ammonium salts. These flame retardants account for about 6% to about 12% of the total mass of the products. 
     However, an order issued on 21 Jun. 2013 by the European Union prohibits the production, distribution, or sale of cellulose insulation materials containing ammonium salts as additives. Substances containing ammonium salts, used as additives in CI may lead to emission of ammonium gas under certain conditions. The ammonium salts identified in the order include ammonium sulfate (Chemical Abstracts Service (CAS) No. 7783-20-2), ammonium dihydrogen orthophosphate (CAS No. 7722-76-1), and diammonium hydrogen orthophosphate (CAS No. 7783-28-0). Different cofactors may promote ammonia emissions, such as the humidity, the pH of the CI, or temperature, among others. 
     Accordingly, research into other potential flame retardant systems has continued. Useful systems may be non-toxic and release no problematic gases during storage, use, or when exposed to ignition sources. 
     SUMMARY 
     An example described herein provides a method for an insulation product. The insulation product includes cellulose fibers and a fire-retardant chemical formulation. The fire-retardant chemical formulation includes calcium chloride. 
     The fire-retardant chemical formulation may include calcium carbonate or calcium hydroxide or both. The ratio of calcium carbonate and calcium hydroxide to calcium chloride may be between about 0.5 and about 0. The fire-retardant chemical formulation may include a molecular sieve or a zeolite. The fire-retardant chemical formulation may include calcium oxide. 
     The insulation product may include a biocidal formulation. The biocidal formulation may include butoxylated alcohols having carbon chains that are greater than about 11 carbons, wherein the carbon chains are linear, branched, or both. The insulation product may include a corrosion inhibitor. The corrosion inhibitor may include disodium hydrogen phosphate. The insulation product may include a surfactant. 
     Another example described herein provides a method for forming an insulation product. The method includes applying a powdered fire-retardant to cellulose fibers, wherein the powdered fire-retardant includes calcium chloride. The method also includes applying a fire-retardant liquid solution to the cellulose fibers, wherein the fire-retardant liquid solution includes calcium chloride. 
     Calcium carbonate, calcium hydroxide, or both, may be blended with calcium chloride to make the powdered fire-retardant. A zeolite may be blended into the calcium chloride to form the powdered fire-retardant. Clinoptilolite may be blended into the calcium chloride to form the powdered fire-retardant. Calcium oxide may be blended into the calcium chloride to form the powdered fire-retardant. 
     The method may include adding a biocide to the fire-retardant solution before applying the fire-retardant solution to the cellulose fibers. The method may include adding a surfactant to the fire-retardant solution before applying the fire-retardant liquid solution to the cellulose fibers. The method may include applying the fire-retardant liquid solution at a ratio to the powdered fire-retardant of about 0.2-3:9.8-7 by weight. 
     The method may include shredding a cellulose source before adding the powdered fire-retardant. A shredded cellulose source may be milled before adding the fire-retardant liquid solution. 
     Another example described herein provides a fire-retardant chemical formulation. The fire-retardant chemical formulation includes a dry powder mixture, that includes calcium chloride. The fire-retardant chemical formulation includes a liquid solution that includes calcium chloride, a biocidal formulation, a corrosion inhibitor, and a surfactant. 
     The liquid solution may include calcium chloride in a range of between about 1 wt. % and about 25 wt. %. The liquid solution may include a biocidal agent in a range of between about 0.01 wt. % and about 1.5 wt. %. The biocidal formulation may include butoxylated alcohols having carbon chains of greater than about 11 carbons, wherein the carbon chains are linear, branched, or both. 
     The corrosion inhibitor may include monosodium dihydrogen phosphate. The monosodium dihydrogen phosphate may be present in a range of between about 0.5 wt. % and about 5 wt. %. A surfactant may be present in a range of between about 0.05 wt. % and about 0.2 wt. %. 
     The dry powder mixture may include CaCl 2 .xH 2 O in a range of between about 2 wt. % and about 90 wt. %, wherein x is 0, 1, 2, 4, or 6, or any combinations thereof. The dry powder mixture may include calcium carbonate or calcium hydroxide or both in a range of between about 2 wt. % and about 60 wt. %. The dry powder mixture may include a zeolite in a range of between about 2 wt. % and about 60 wt. %. The dry powder mixture may include calcium oxide in a range of between about 0 wt. % and 5 wt. %. A ratio between the liquid solution and the dry powder mixture may be about 0.2-3:9.8-7 by weight. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The advantages of the present techniques are better understood by referring to the following detailed description and the attached drawings. 
         FIG. 1  is a schematic diagram of the production of cellulose insulation, in accordance with examples. 
         FIG. 2  is a schematic diagram of the production of cellulose insulation, in accordance with examples. 
         FIG. 3  is method for forming cellulose insulation, in accordance with examples. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description section, specific embodiments of the present techniques are described. However, to the extent that the following description is specific to a particular embodiment or a particular use of the present techniques, this is intended to be for exemplary purposes only and simply provides a description of the exemplary embodiments. Accordingly, the techniques are not limited to the specific embodiments described below, but rather, include all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims. 
     Most of the present chemicals used for cellulose insulation (CI) production may be somewhat toxic and may have less than optimal effects on the environment. New formulations of chemicals for CI products should provide sufficient fire-retardant or fire suppressant properties, while being resistant to microorganisms and fungi. Further, the additives may provide some resistance to corrosion and be easy for use in the application and manufacturing process. 
     The American Society for Testing and Materials (ASTM) has issued two standards pertaining to CI. ASTM C 739-17 covers the composition and physical requirements of chemically treated, recycled cellulosic fiber (wood-base) loose-fill type thermal insulation for use in attics or enclosed spaces in housing and other framed-buildings within an ambient temperature range of about −45.6° C. to about 82.2° C. (about −50° F. to about 180° F.) by pneumatic or poring application. The second standard, ASTM C 1149-11, covers the physical properties of self-supported, spray applied cellulosic fibers intended for use as thermal and acoustical insulation, or both. ASTM C 1149-11 covers chemically treated cellulosic materials intended for pneumatic application in temperature range below about 82.2° C. (180° F.). Both standards address density, thermal resistance, smoldering combustion, fungal resistance, corrosion, moisture vapor absorption and odor. 
     These standards required that all CI must pass flammability and corrosiveness tests. For example, under preceding specifications issued by the Consumer Product Safety Commission (CPSC) standards, CI must have a flame spread rating of from 0 to 25 feet when placed in a 25-foot Steiner tunnel and ignited. In addition, CI must pass a corrosiveness test. For example, corrosion testing of a CI tested may not result in perforations in copper, aluminum, or steel coupons during a 14-day test. 
     Examples described herein provide a fire-retardant chemical formulation, which may be used in or a CI product for fire retardancy, for example, as determined by the ASTM standards (ASTM C 739-17 and ASTM C 1149-11). The fire-retardant chemical formulation for the CI product may be implemented in existing production facilities, with minimal addition of production steps or production machinery. The fire-retardant chemical formulation may be economical, for example, having lower material costs and operating expenses in comparison to existing chemical formulations for fire retardancy, such as boron salts. Further, the formulation may be considered as non-toxic and environmentally friendly. 
     The new chemical formulation may be based on calcium compounds, for example, calcium chloride, calcium carbonate, or calcium hydroxide. The calcium chloride may be anhydrous (CaCl 2 ), or in the form of a hydrate, such as CaCl 2 .H 2 O, CaCl 2 .2H 2 O, CaCl 2 .4H 2 O or CaCl 2 .6H 2 O. The use of hydrates may provide some advantages, because the hydrated calcium chloride molecule dehydrates during the heating absorbs energy, lowering the temperature, and releases water vapor which may further inhibit flame spread. Other compounds may be used in addition to, or instead of the calcium chloride, such as calcium hydroxide, calcium carbonate, and zeolites. 
     The dehydration reaction is shown in the chemical formula of equation 1. 
       CaCl 2 .6H 2 O→CaCl 2 .4H 2 O+2H 2 O→CaCl 2 .2H 2 O+4H 2 O→CaCl 2 +6H 2 O  Eqn. 1
 
     The dehydration of CaCl 2 .6H 2 O to CaCl 2 ) starts already at room temperature and proceeds in three reaction steps. The overall dehydrations are completed at temperatures below 140° C. The obtained overall reaction enthalpies are 1,153 kilojoules/kilogram (kJ/kg) for CaCl 2 .4H 2 O, and the total enthalpy for CaCl 2 ) is about 2,630 kJ/kg. 
     Another calcium compound that may be used in the formulation is calcium carbonate (CaCO 3 ). CaCO 3  decomposes at a temperature of about 600° C., according to the chemical formula of equation 2. 
       CaCO 3 →CaO+CO 2   Eqn. 2
 
     The enthalpy of this reaction is about 12,070 KJ/kg, which will absorb a substantial amount of energy during the decomposition process. The decomposition releases CO 2 , which may further inhibit flammability. These two components when used together have a very high thermal capacity and can absorb very large quantity of heat in case of combustion. A ratio of the calcium chloride to the calcium carbonate may be between about 10 and about 0. 
     Instead of, or in addition to, the calcium carbonate (CaCO 3 ), another calcium compound may be used, calcium hydroxide (Ca(OH) 2 ), added as lime. The calcium hydroxide may react over time with carbon dioxide (CO 2 ) in the air to produce calcium carbonate, according to the chemical formula of equation 3. 
       Ca(OH) 2 +CO 2 =CaCO 3 +H 2 O  Eqn. 3
 
     Calcium carbonate may absorb a large amount of energy during decomposition. Further, water produced during the reaction of equation 3 may be retained in the formulation, and may also absorb heat through evaporation. 
     Some of the calcium compounds described herein are hygroscopic, and may absorb substantial amounts of water. This may lead to clumping and other problems during production. Accordingly, a desiccant may be added to lower the amount of water absorbed by the compounds. In some examples, calcium oxide is added to a dry powder mixture to slow water absorption by other calcium compounds. The calcium oxide absorbs water to form calcium hydroxide according to the chemical formula of equation 4. 
       CaO+H 2 O═Ca(OH) 2   Eqn. 4
 
     Further, the calcium hydroxide absorbs more water to form a hydrate, e.g., Ca(OH) 2 .x H 2 O, where x may be two, four, or six. 
     Other compounds that absorb water may be used in the dry powder mixture, both for releasing the water during fire protection and for providing a desiccant capability. For example, molecular sieve may be used. As defined herein, a molecular sieve is a material with pores of uniform size, including zeolites, porous glass, montmorillonite, and artificial zeolite-like structures that can adsorb water molecules. In various examples, a zeolite, such as clinoptilolite, is used in the formulation. Clinoptilolite is a natural zeolite with a microporous structure that provides a very high surface area. The role of clinoptilolite, or other zeolites, in this formulation is to retain water in the bulk material. The water has a high heat capacity and can absorb a large amount of heat. Further, the desorption of water from the zeolite absorbs a substantial amount of heat. As the water is released in the form of steam, this may provide further fire inhibition by cutting off oxygen from the burning material. 
     Clinoptilolite is an aluminosilicate with a microporous arrangement of silica and alumina tetrahedra. The chemical formula of clinoptilolite is (Na,K,Ca) 2-3 Al 3 (Al,Si) 2 Si 13 O 36 .12H 2 O. Clinoptilolite is white to white-yellowish crystal powder and can adsorb up to 15% of water. In addition to zeolites, other molecular sieves, formed from Si, Al, and O, and metals such as Ti, Sn, and Zn, may be used to hold water in the mixture. 
     The use of calcium hydroxide or zeolites instead of, or in addition to, the calcium carbonate decreases the hydroscopic nature of the mixture, allowing its use in a wider range of climates. For example, a mixture of calcium chloride and calcium hydroxide may resist forming a cake or a sludge, even at high humidity levels, such as about 95% to 98% relative humidity. Further, even at low concentrations relative to the calcium chloride, such as 10% to 20% calcium hydroxide, the use of these compounds may allow the powdered fire-retardant mixture to remain dry, for example, in powder form, long enough for application to a cellulosic insulation, for example, around two hours in some blends. In some examples, the ratio of calcium carbonate to a combined amount of calcium chloride and calcium hydroxide is between about 0.1 and about 0. 
     In addition to the calcium compounds, other components may be used, such as biocidal formulations and corrosion inhibitors. The biocidal formulations may be included to inhibit the growth of microorganisms and fungi. Commercial agents, such as butoxylated alcohols including carbon chains of greater than about 12 carbons, wherein the carbon chains are linear or branched, may be used. One example of these types of compounds, Plurafac® LF 221, is available from BASF Corporation of Ludwigshafen, Germany. 
     Any number of other biocidal formulations may be used instead of, or in addition to, the butoxylated alcohols, and other biocidal formulations may be used. Biocidal formulations that may be used may include preservatives such as carbamates, disodium octaborate tetrahydrate, quaternary ammonium-based formulations, silver-based materials, or copper-based materials, among many others. Another example of a biocide that may be used in various formulations is Polyphase® 678 from the Troy Chemical Company. This material is a mixture of 2-benzimidazole carbamic acid, as the methyl ester, 3-iodo-2-propynyl butylcarbamate, and kaolin. As biocidal formulations may be used in low amounts, have low vapor pressure, or both, biocidal formulations may be selected that are compliant with regulations. 
     A corrosion inhibitor may be added to decrease or prevent corrosion of metal parts, such as pipes, conduits, and wires that may be in contact with the CI in wall or ceiling cavities. In various examples, disodium hydrogen phosphate (Na 2 HPO 4 ) is added as a corrosion inhibitor. In other examples, monosodium dihydrogen phosphate (NaH 2 PO 4 ) is added as a corrosion inhibitor. In other examples, other corrosion inhibitors, such as organic phosphate salts, calcium nitrate, zinc oxide, or N,N′-dimethylaminoethanol, among others, are used instead of, or in addition to, the phosphate salts. 
       FIG. 1  is a schematic diagram of a system  100  that may be used to produce a cellulosic insulation, in accordance with an example. It can be noted that this system  100  is merely one example. Fewer units may be used, for example, if a feed  102  has a consistent composition such as recycled newspapers. More units may be used if different types of feed  102  are used, such as newspaper, shredded office paper, cardboard, mixed paper, or other cellulose sources, including fabric. 
     In this example, a recycled paper storage  104 , such as a bin, hopper, warehouse, or other storage, feeds a conveyor  106 . The feed  102  may be placed on the conveyor  106  either manually or automatically. The conveyor  106  may empty the feed  102  into a primary mixer  108 . In the primary mixer  108 , the feed  102  may be ripped apart and declumped, for example, breaking stacks of paper into loose papers. Further, metal, plastic and other contaminants, such as staples, fabric, and paper clips, among others, may be ripped free from the feed  102 . 
     The declumped feed may be fed from the primary mixer  108  onto a second conveyor  110 . A magnet  112 , or other separator, such as an air jet, or density separator, over the second conveyor  110  may be used to pull metal fragments and other debris from the declumped feed. Once metal scraps are removed, the second conveyor  110  may add the declumped feed to a shredder  114 . In the shredder  114 , the declumped feed may be torn into small pieces, for example, the pieces may be around 5 cm (2 inches) long. In some examples, such as if the feed  102  is primarily newspaper, the primary mixer  108  may not be present, and the feed  102  may be fed directly to the shredder  114 . 
     The fire-retardant chemical formulation may be added at one or more places in the process, for example, with a dry powder mixture  116  added at one place in the process and a liquid solution  118  added another place in the process. In one example, the dry powder mixture  116  may be blown into the shredder  114  from a powder storage vessel  120  using an air stream  122 . The air stream  122  may carry the fine particles of the dry powder mixture  116  and effect agitation of the material in the shredder  114 , such as the small pieces and cellulose fibers, providing an efficient coverage of the surface area. 
     In another example, the dry powder mixture  116  is added to the shredder using a gravity feed device, such as a screw feeder or a manual feed through a hatch. In this example, the shredding devise itself, such as the blades or mill plates, may perform the mixing. 
     The dry powder mixture  116 , or powdered fire-retardant, may include a mixture of calcium chloride and calcium hydroxide or calcium carbonate, or a mixture of calcium chloride, calcium carbonate, and calcium oxide. The calcium oxide may function as a desiccant to absorb water and decrease clumping of the dry mixture. In various examples, the dry powder mixture comprises calcium oxide in a range of between about 0 wt. % and about 5 wt. %. In some examples, zeolites may be included instead of, or in addition to, the calcium oxide. 
     A portion of the calcium chloride may be replaced with calcium hydroxide, as described herein. The calcium chloride may be anhydrous, or may include one, two, four, or six waters of hydration, or any combinations thereof, for example, CaCl 2 .xH 2 O, where x is 0, 1, 2, 4, or 6, or any combinations thereof. The dry powder mixture  116  may include between about 2 wt. % and about 90 wt. % of calcium chloride compounds, such as the anhydrous or the hydrated calcium chloride. In some examples, the dry powder mixture  116  may include between about 20 wt. % and about 70 wt. % of calcium chloride compounds. The amount of the calcium chloride compounds selected, and the waters of hydration selected, may depend upon the target environment for the cellulose insulation. For example, in a high humidity environment, such as the Gulf Coast of the United States, the amount of calcium chloride compounds may be reduced in the dry powder mixture  116 . Further, calcium oxide, calcium hydroxide, or a zeolite may be added to further decrease water adsorption in these environments. In a low humidity environment, such as the northern Midwest regions of the United States, the amount of calcium chloride compounds may be increased in the dry powder mixture  116 . Before mixing with the cellulosic material, chemicals from new chemical formulation in the present invention may be ground into a powder to allow good mixing and adhesion with the cellulosic material. In some examples, the dry powder mixture  116  may be added as a batch into the cellulosic material in the shredder  114  without using an air stream  122 . In this example the cellulosic material and the dry powder mixture  116  would be blended by the shredder  114 . 
     The cellulosic material from the shredder  114  may be transferred to a fiberizer  124  through a conveying system  126 . The conveying system  126  may include a conveyor belt or may be an air transfer line. In the fiberizer  124 , the cellulosic material may be milled to form fine fibers, for example, around 4 mm in length. In some examples, the shredder  114  and the fiberizer  124  may be a single unit that performs both functions. In these examples, the dry powder mixture  116  may be added as the cellulosic material is first shredded, and the liquid solution  118  may be sprayed in after fine fibers are formed. 
     The liquid solution  118 , of the fire-retardant chemical formulation, may be mixed in a liquid solution storage tank  128  then sprayed, for example, through one or more spraying nozzles  130  onto the cellulose fibers. A pump  132  may be used to transfer the liquid solution  118  from the liquid solution storage tank  128  to the spraying nozzles  130 . To improve the wetting of cellulosic fibers with the liquid solution  118 , a small quantity of a surfactant may be added to the solution. The surfactant may include any number of compounds, such as 4-(d-dodecyl) benzenesulfonate, sodium stearate, ammonium lauryl sulfate, sodium lauryl sulfate, quaternary ammonium salts, benzalkonium chloride, or nonylphenol ethoxylate, among others. The surfactant may be a commercial detergent formulation, such as Zep@ detergent, available from Zep Superior Solutions of Atlanta, Ga., USA, Alconox® detergent, available from Alconox Inc. of White Plains, N.Y., USA, Surfonic N-95, available from Huntsman Chemical, among other commercial detergents, such as Dawn® detergent, available from the Procter &amp; Gamble of Cincinnati, Ohio, USA. Spraying the liquid solution  118  may help to suppress dust formation from the cellulose fibers and powdered chemicals. The fire-retardant chemical formulation may also reduce dust, for example, up to about 80% over other formulations, up to about 90%, up to about 95%, or higher, as measured by particulates content over the insulation. The dust reduction may prevent the loss of powder chemicals and small cellulose particles, which may also reduce production costs. 
     The liquid solution  118  may include calcium chloride in a range of between about 1 wt. % and about 25 wt. %. As for the dry powder mixture  116 , the amount of calcium chloride in the liquid solution  118  may be adjusted based on the ambient conditions of use for the cellulose insulation. A biocidal formulation, such as the butoxylated alcohol, or a biocide from the Polyphase® family of biocides, from the Troy Corporation, may be added to the liquid solution  118  in a range of between about 0.01 wt. % and about 1.5 wt. %. The amount of the biocidal formulation added to the cellulose insulation may be increased or decreased, for example, depending on the source of the cellulose fibers or the specific biocidal formulation used. In some examples, the pH of the liquid solution  118  is adjusted with the addition of sodium hydroxide to protect the biocide. In these examples, the pH may be less than about 4 before the addition of the sodium hydroxide, and between about 5.5 and about 7.0 after the addition of the sodium hydroxide. 
     The corrosion inhibitor, such as the monosodium dihydrogen phosphate described herein, may be added to the liquid solution  118  in a range of between about 0.1 wt. % and about 5 wt. %. The amount of the corrosion inhibitor may be increased or decreased, for example, depending on the humidity of the target environment for the cellulose insulation, the amount of chloride ions that are present in the formulation, or the target location for the cellulose insulation, such as in a location that is not in contact with metal. 
     As described herein, the dosage of the chemicals in the fire-retardant chemical formulation may be adjusted based on the ambient conditions, such as humidity, temperature, and the like. As the moisture content in the final CI product depends on ambient conditions the ratio between the liquid solution  118  and the dry powder mixture  116  may also be adjusted to obtain the desired density and moisture content of the final CI product. For example, the ratio between the liquid solution  118  and the dry powder mixture  116  may be in a range of from about 0.2 to 9.8 to about 3 to 7. This may correspond to a ratio between the liquid solution  118  and the dry powder mixture  116  of between about 2% and about 30% by weight. 
     The CI formed in the fiberizer  124  may be transferred through a conveying system  134  to a packager  136 . The conveying system  134  may be an air conveying system moving the CI through a pipe. At the packager  136  the CI may be injected into bags and compressed to form bales. The bales may be moved to palletizer  138  and wrapped on pallets that may be shipped out, as indicated by reference number  140 . 
       FIG. 2  is schematic diagram of another system  200  that may be used to produce a cellulosic insulation, in accordance with an example. Like numbered items are as described with respect to  FIG. 1 . The addition points for the dry powder mixture  116  and the liquid solution  118  may be changed, as shown in  FIG. 2   
     The liquid solution  118  may be added to the shredder  114  from the liquid solution storage tank  128 . For example, the liquid solution  118  may be sprayed into the shredder from the spraying nozzles  130 . The liquid solution  118  may be added to vessels associated with the shredder  114 , such as a cyclone, drop box, or another vessel feeding into the shredder. 
     The dry powder mixture  116  may then be added after the fiberizer  124 . this may be performed by adding the dry powder mixture  116  to a drop box  202  after the fiberizer  124 . The drop box  202  is a density settling device used to remove contaminates  204 , such as plastics and metals, before packaging. 
       FIG. 3  is a block diagram of a method  300  for forming cellulose insulation using the fire-retardant chemical formulation described herein. The method  300  may begin at block  302  when recycled paper is declumped. This may involve breaking stacks and separating adjacent sheets of paper, for example, into individual sheets or crumpled sheets. The paper may be ripped into large fragments, and staples, paper clips, and other metal fragments may be ripped free of larger sheets. At block  304 , metal fragments may be removed, for example, using a magnet placed over conveyor belt. 
     At block  306 , the paper may be shredded to form fragments of about 5 cm in a longest dimension. The shredding may be performed by rotating shredder blades. At block  308 , a first portion of the fire-retardant chemical formulation may be added to the fragments. The first portion may include a powered fire-retardant, which may include calcium chloride and calcium carbonate or calcium hydroxide in the ratios described for the dry powder mixture  116  of  FIG. 1 . The dry powder mixture may include zeolites in some examples. In some examples, the first portion may be a liquid fire-retardant solution, which may include the components described for the liquid solution  118  of  FIG. 1 . 
     At block  310 , the fragments, or shredded cellulose source, may be milled to form cellulose fibers, for example, of about 4 mm in length. The milling may be performed by a hammer mill. At block  312 , a second portion of the fire-retardant chemical formulation may be added to the cellulose fibers. The second portion may include a fire-retardant solution that includes calcium chloride. As described with respect to the liquid solution  118 , the fire-retardant solution may include a number of other ingredients, such as biocidal agents, corrosion inhibitors, and a surfactant, among others. The fire-retardant solution may be sprayed on the cellulose fibers, providing an even distribution, and helping to suppress dust formation. In some examples, the second portion may include a powered fire-retardant, which may include calcium chloride and calcium carbonate or calcium hydroxide in the ratios described for the dry powder mixture  116  of  FIG. 1 . The dry powder mixture may include zeolites in some examples. 
     At block  314 , the cellulose insulation is packaged. This may be performed, for example, by compressing the CI into a bale within the bagging machine, forcing the bale into a bag, and then sealing the bag. Depending on the bag type, the ceiling may be a heat seal, a glue seal on a paper bag, or combination thereof. At block  316 , the packages may be palletized. This may be performed by stacking bales onto pallets and shrink wrapping the stacks. 
     Not every block may be performed in every example. If the shredding and milling are performed at the same time, an initial addition of the powdered fire-retardant may be made, and then as the fragments are milled, or shredded, into fibers the fire-retardant solution may be sprayed on the fibers. 
     Example 
     Examples of formulations that may be used are presented in Table 1. In Table 1, all amounts are presented as weight percentages. As described with respect to  FIG. 1 , the dry powder mixture  116  can be mixed with the fiber, or cellulosic insulation (CI), in a first process, while the liquid solution  118  can be applied to the CI in a second process. 
     In addition to these examples, many other combinations may be used, as described herein. In other examples, the formulations shown in Table 1 are modified to include molecular sieves in addition to or instead of the calcium oxide. In other examples, the amount of the calcium chloride dihydrate in the liquid solution  118  are increased up to about 15%, or higher, to improve flammability and ignition properties, such as measured by a smolder-combustion test. 
     While the present techniques may be susceptible to various modifications and alternative forms, the embodiments discussed above have been shown only by way of example. However, it should again be understood that the techniques is not intended to be limited to the particular embodiments disclosed herein. Indeed, the present techniques include all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example formulations 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Range 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
                 Ex. 5 
                 Ex. 6 
               
               
                 CHEMICAL NAME 
                 wt. % 
                 wt. % 
                 wt. % 
                 wt. % 
                 wt. % 
                 wt. % 
                 wt. % 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 DRY POWDER MIXTURE: 
                   
                   
                   
                   
                   
                   
                   
               
               
                 CALCIUM CHLORIDE DIHYDRATE 
                  38-100 
                 48.0 
                 40.0 
                 50.0 
                 57.5 
                 69.0 
                 79.0 
               
               
                 CALCIUM CARBONATE 
                 58-0  
                 48.0 
                 58.0 
                 47.5 
                 40.0 
                 27.5 
                 19.0 
               
               
                 CALCIUM OXIDE 
                 4-0 
                 4.0 
                 2.0 
                 2.5 
                 2.5 
                 3.5 
                 2.0 
               
               
                 LIQUID SOLUTION: 
               
               
                 WATER 
                 70-90 
                 84.5 
                 84.99 
                 84.49 
                 79.39 
                 75.69 
                 81.99 
               
               
                 CALCIUM CHLORIDE DIHYDRATE 
                  1-25 
                 10.1 
                 8.5 
                 10.8 
                 14.8 
                 19.8 
                 22.6 
               
               
                 MONOSODIUM PHOSPHATE 
                 0.1-5     
                 2.0 
                 3.0 
                 2.0 
                 2.5 
                 1.8 
                 2.5 
               
               
                 POLYPHASE (LIQUID) 
                 0.1-1.5 
                 1.3 
                 0.5 
                 0.7 
                 0.8 
                 0.9 
                 1.2 
               
               
                 SODIUM HYDROXIDE 
                 0.1-4     
                 2.0 
                 3.0 
                 2.0 
                 2.5 
                 1.8 
                 2.5 
               
               
                 LIQUID DETERGENT 
                     0-0.1 
                 0.04 
                 0.01 
                 0.01 
                 0.01 
                 0.01 
                 0.01