This invention is directed to fibrous cellulose spray-on insulation, adhesives used therewith, and to methods for their use.

The prior art discloses a wide variety of spray-on cellulose insulation materials and systems. Certain prior art compositions used in spray-on insulation systems include an adhesive which is a mixture of sodium silicate and an acrylic resin. A homogeneous mixture of these two ingredients is achieved by combining them with a high speed shearing-mixing action. After a period of time the ingredients of the mixture can settle out and separate from each other. Under prolonged storage conditions such a mixture will gel and then require laborious re-mixing, e.g. with a high speed mixer. Other disadvantages of such adhesives include: limited flexibility; limited freeze/thaw (temperature differen¬ tial) stability; and limited water resistance; and the requirement for additional handling, mixing, etc. at a job site. Such prior art compositions are also typical¬ ly used in a ratio of water to adhesive 3:5; and at a ratio of such a mixture (water + adhesive) to fiber of .23 gallons of mixture to about one pound of fiber. It may be desirable to be able to use less adhesive concentrate to reduce transport cost and material ex¬ pense.

Polyvinyl alcohol ("PVOH") is a known adhesive which, for many applications is dissolved in water prior to use and "cooked". Typically this cooking involves dispersing particles of PVOH in water at ambient tem¬ perature and raising the resulting mixture's temperature to between 180 and 205 degrees Fahrenheit (85 to 96 degrees C) for about 30 minutes. It is known in certain PVOH cooking processes to add an acidic medium (e.g. boric acid) to PVOH during the cooking process to im-

prove the wet strength, water resistance and fire retar¬ dancy of the resulting material. To prevent gelling, the pH of a homogeneous amount of PVOH and boric acid is adjusted, from the range of 6.7 - 7.3 to between about 4.5 to 4.7, e.g. by adding an acid (such as citric acid or phosphoric acid). The pH is monitored and maintained between 4.5 to 4.7 as boric acid is added. Addition of acid to the PVOH can result in a more corrosive material which must be safely contained, packaged, transported and used. Also, the amount of acid that can be added is limited by the saturation level of water at ambient temperature.

The present invention provides a composition for spray-on insulation, said composition including polyvi¬ nyl alcohol cooked without an acidic medium and cellu¬ lose fibers combined with an acidic medium. Embodiments of the spray-on insulation material exhibit improved water resistance, fire retardancy, and wet strength.

The present invention, in certain embodiments, provides a two component spray-on insulation. One component is polyvinyl alcohol ("PVOH") cooked without the addition of an acidic medium; or such PVOH with an additive such as an acrylic polymer. Another component is a composition which includes cellulose fibers (e.g. as described in U.S. Patents 4,360,440; 5,082,563; 5,195,465; and 5,352,780) and a cross-linking substance, e.g. an acidic medium (solids and/or liquid). Examples of the cross-linking medium include (but not limited to) granular boric acid solids (e.g. about the size of table salt granules) for supplying a borate ion such as those commercially available from U.S. Borax Co. These solids may be powderized to reduce them in size (e.g. to about the size of particles of commercially available baby powder). Milling may typically be carried out at a temperature of about 165° F with an air flow through the

mill. Air flow may be used to convey fibers in various processing steps resulting in a moisture content in the fibers of about 10 to 15 percent by weight. In other embodiments liquid borax may be used.

In certain embodiments the cellulose fibers and acidic solids are mixed together; in other embodiments they are ground together in a processing mill (e.g. a hammer mill available from Williams Co., Grundler Co., Jacobs Co., or Bliss Co.). About 75 to 85 pounds of cellulose fibers (2.5 mm in an average largest dimen¬ sion) may be mixed or milled with about 15 to 25 pounds of powdered boric acid solids. The treated fibers may have ingredients ranging, by weight, as follows (the total percentage of finished product having components within the stated ranges equalling one hundred percent): between 75% to 85% cellulose fibers between 10% to 25% solid boric acid between 0% to 12% (in certain embodiments 8% to 12%) sprayed-on aqueous boric acid.

Examples include: 75% cellulose fibers and 25% solid boric acid; 75% cellulose fibers, 17% solid boric acid, 8% aqueous boric acid; and

81% cellulose fibers, 10% solid boric acid, 9% aqueous boric acid.

Fibers mixed with the acidic medium and/or milled with the acidic medium may also be sprayed with an aqueous liquid acid solution to further coat and/or impregnate them with the acidic medium. The fibers may be sprayed with the acidic medium using a one-nozzle device or using a two-nozzle device as shown, e.g., in Fig. 7 of U.S. Patent 5,429,741 (incorporated in its entirety herein by reference).

Cellulose fibers may be fed through a first hose to

an insulation composition spray nozzle and the acidic medium may be fed through a separate second hose to the nozzle so that the acidic medium is applied to the cellulose fibers within and as they leave the nozzle. Adhesive composition is introduced through another hose to the nozzle.

In one spray-on insulation system, the above de¬ scribed mixture of cellulosic fibres and acidic solids is introduced through one hose to an insulation spray nozzle (e.g. as shown in U.S. Patent 4,187,983) and a liquid PVOH adhesive is introduced into the spray nozzle through another hose. In other embodiments, the liquid PVOH adhesive may be mixed with a liquid acrylic poly¬ mer, or, acrylic resin or emulsion, such as (but not limited to) FT-9 PVC material, B.F. Goodrich Co.; 1415 vinyl acrylic material, Rhone-Poulenc Co.; 6326 vinyl acrylic material, Rohm & Haas Co.; 1845 vinyl acrylic material, B.F. Goodrich Co.; 1199 Styrene acrylic latex, Rhone-Poulenc Co.; 526 BP vinyl acetate, Air Products Co.; and Res. 7800 polyvinyl acetate copoly¬ mer, Unocal Co.; and the mixture is fed to the spray nozzle. The added acrylic polymer increases the tough¬ ness, water resistance fire retardancy, elasticity and bonding ability of the resulting product.

Fibers treated as described herein with ground-in acidic solids and/or with sprayed on liquid acid may be used in a spray-on insulation with prior art PVOH that is cooked with an acidic medium, and with such PVOH that is cooked with the addition of additional acid as de¬ scribed above. Such adhesives are usable in embodiments similar to those described herein in place of the adhe¬ sives according to this invention and in the same pro¬ portions.

In certain embodiments of the present invention fibers and methods of their use are provided which make

available more boric acid for the final product than prior art materials and methods in which boric acid is added to cooking PVOH.

Embodiments of the sprayed-on insulation of the invention are self-extinguishing and exhibit high water resistance, fire retardancy, bonding and wet strength, and can be applied up to four inches in depth and some¬ times up to eight inches in depth. The invention further provides methods for using such materials.

Cellulose fibers may be acid treated by introducing boric acid in powder form into a hammer mill with cellu¬ lose fibers. Boric acid powder (17 - 22 pounds) may be introduced into the hammer mill where it is combined with fibres (83 - 78 pounds) and milled together. The fiber/boric acid ratio, by weight, may be 41:9. The fibers may have an average largest dimension of 2.5 mm.

The fibers with acid in and on them may then be fed to a treatment vessel wherein they are sprayed with a solution of boric acid/borax and water (e.g. an aqueous solution which is 15 to 25% by weight liquid borax/boric acid). Fibres (about 75 pounds) may be treated with chemicals (about 25 pounds) which include 90% to 95% powdered boric acid solids by weight and 5% to 10% liquid boric acid by weight, producing about 100 pounds of treated fibers.

Fibers from the hammer mill (with or without ground-in acidic solids) may also be treated by immer¬ sion in a container of boric acid solution. The total boric acid in the treated product fibers can be between 50% to 100% powdered solids and between 0% to 50% liquid boric acid (in aqueous solution); in such embodiments the acidic medium (in all forms) is between 15% to 30% by weight of the treated fibers product. The fibers may then be fed to one hose of a multi-component spray nozzle. A mixture of PVOH (e.g. PVOH #107 commercially

available from Air Products Co.) and acrylic resin (see e.g. U.S. Patent 4,360,440 fully incorporated herein by reference) may be fed to another hose of the spray nozzle. The PVOH/acrylic resin mixture (e.g. in an amount of 0.23 gallons for each pound of fibres) may be prepared by pouring the components into a container and then mechanically mixing them, e.g. with a direct drive exterior dual helix shaft rotated at 1750 r.p.m. for five to ten minutes. Pumps, e.g. commercially avail¬ able diaphragm pumps, may be used to pump the adhesive mixture to the spray nozzle and to pump the treated fibers to the spray nozzle, and thereby produce a spray- on insulation composition.

A spray-on composition according to this invention can be effectively sprayed onto a variety of substrates such as wood, concrete, plastic, metal, ceramic, sheet rock, and paintable surfaces to any desired depth up to eight inches (in certain aspects to a desired depth up to four inches) without the undesirable falling out of flakes or chunks of material.

An aqueous acidic medium solution for spraying onto fibers treated in a hammer mill as described above may be prepared by mixing about 700 gallons of water, about 2018 pounds of powderized boric acid, and about 2845 pounds of Borax material, e.g. Borax commercially avail¬ able from U.S. Borax Co. The water is added to a glass lined vessel, and is heated by a boiler. When the temperature reaches 150°F., powderized boric acid is introduced into the vessel. It takes approximately 30 - 45 minutes to add the boric acid. Then the borax is introduced into the vessel by conveyor belt while the vessel's contents is agitated. It takes approximately one hour to add the borax. The temperature of the total solution is raised to 180° F while agitating the solu¬ tion. If the temperature in the vessel is permitted to

fall below 110° F, components of the solution will start to separate out, crystallize, and settle out. The resulting solution has a density of 10.20 pounds/gallon; there is about 4.64 pounds of chemical (boric acid powder plus borax) in a gallon of resulting solution; and pH of the solution is 7.33 at 110° F.

In one embodiment the commercially available granu¬ lar boric acid has a particle size of 100 mesh (0.025cm or.01" average largest dimension). The granular boric acid is conveyed by a screw-conveyor to a hopper from which it is fed to a pulverizer which is driven by 15 h.p. motor at 3600 R.P.M. and has sieve size of 0.09cm (0.035"). Finished powdery boric acid with an average largest dimension of 0.09cm (.035") drops into a collec¬ tion hopper.

In one embodiment a known weighed amount of powder boric acid is put in a large blender and a known amount of aluminium sulfate and pigment are added. The ratio

(by weight) or various ingredients is as follows:

Boric Acid 65.30% - 100%

Aluminium Sulfate 0 to 24.25% (optional)

Pigment 0 to 10.45% (optional)

The chemicals and pigment are mixed by a ribbon blender to a homogeneous mixture. Then the mixture is dropped into a small mixing blender, then fed into a finishing mill by a d.c. drive chemical screw delivering an exact amount of finished dry-chemical-to-fiber in the mill which are mixed thoroughly with cellulose fibers while grinding. Treated fibers (i.e. with ground-in powderized boric acid solids, aluminium sulfate and pigment) are then drawn through a screen in the mill due to vacuum created by a downstream finishing fan. The treated fibers are then passed through a pipe. Fire retardant liquid chemical (aqueous boric acid solution prepared as described above) is fed to two nozzles in

the pipe by a chemical metering pump and sprayed onto the treated fibers flowing through the pipe. The re¬ sulting mixture then goes through a fan to a cyclone which separates out undesirable fines from the fibers. The fibers are then fed to a bagger hopper and packaged into a plastic bag.

Table I presents data illustrating wet strength of a spray-on insulation product according to the present invention. Products A and C were not treated with powdered acidic solids. Product A was prepared by forming a one-inch thick piece of material with cellu¬ lose fiber (without boric acid treatment) sprayed with an adhesive, e.g. Air Products PVOH #107. About .23 gallons adhesive mixture were sprayed with each pound of fiber. "Reduce 5:1" means 5 parts of water were used for each part of adhesive mixture. "Set Time" is the time the sample was allowed to set prior to testing. "Tare Wt." means the weight of test apparatus connected to the test sample. "Add Wt." is the amount of addi¬ tional weight hung from the sample during testing. "Total Wt." is the weight a sample supported at failure (tearing of the material). "Time To Failure" is the time taken for the sample to fail once the "Total Wt." was applied. As noted, samples A and C failed fairly quickly with relatively small weights applied to them.

Sample B was produced as described above according to the present invention by treating cellulose fiber (average largest dimension 2.5 mm; moisture content 10% to 15% by weight) with powdered boric acid solids ground-in and aqueous boric acid solution sprayed-on. Such samples supported significantly more weight (indi¬ cative of increased ability to "hang" or spray material on a substrate to a significantly increased depth).

Sample C is material as described in U.S. Patent 4,360,440.

Sample D is material as described in U.S. Patent 4,360,440; but which has been treated with boric acid as was Sample B.

Each Sample A - D was a sample piece 6" x 8" x 1".

Table II presents data for bond strength for a variety of adhesive mixtures according to the present invention.

"SOURCE" indicates the company from which the ingredient is commercially available:

"AP" is Air Products Co.;

"RH" is Rohm & Haas Co.;

"BFG" is B.F. Goodrich Co.;

"DS" is Diamond Shamrock Co. "

TYPE" indicates the product's identifying number.

"7200.5" is AP 7200 diluted half-and-half with water.

"PVOH" is polyvinyl alcohol (e.g. #107 available from Air Products Co. which is not cooked with additional acid added and is not cooked with boric acid).

"%A" and "%B" mean the percent by volume of each component in the resulting mixture.

"MIX" indicates water-to-adhesive mixture ratio by volume.

"Film Shrink None" means there was no visible loss of contact from edges of a tray holding the sample.

"Film Shrink Little" means there was visible loss of such contact.

"Film Shrink Some" means such visible loss of contact was readily evident.

"Film Elast Excel." means there was elongation equal to about 25% or more of original length when the sample was pulled at both ends simultaneously.

"Film Elast Good" means such elongation of at least 25%.

"Film Strength Excel." means able to support 100

times its own weight.

"Film Strength Good" means able to support 50 times its own weight.

"Bond P.S.F." is bond strength in pounds per square foot of a piece of the resulting material 13" x 13".

"Substr." indicates a substrate to which the adhe¬ sive mixture was applied and from which the 13" x 13" piece (one inch thick) was removed.

"Gal" is galvalume steel.

"P.M." is painted metal (steel).

"Wet Strength" means strength of a fibrous mass prior to drying.

Tested films were 1" x 12".

Materials indicated in the last two entries were prepared with the adhesives described in U.S. Patent 4,360,440 without boric acid.

It will be appreciated that modifications may be made to the embodiments described herein without depart¬ ing from the invention.

Table 1

Product Reduce Set Time Tare Wt Add Wt Total Wt Time to (grams) (grams) (grams) Failure

5:1 5 Min 80 60 140 35 Sec

A 5:1 10 Min 80 57 137 43 Sec

5:1 30 Min 80 81 161 100 Sec

Product Reduce Set Time Tare Wt Add Wt Total Wt Time to (grams) Failure

5:1 5 Min 80 220 300 230 Sec

B 5:1 10 Min 80 611 691 270 Sec

5:1 30 Min 80 580 660 200 Sec

Product Reduce Set Time Tare Wt Add Wt Total Wt Time to Failure

4:1 5 Min 82 0 <82 0 Sec

C

4:1 10 Min 82 0 <82 0 Sec

Product Reduce Set Time Tare Wt Add Wt Total Wt Time to Failure

4:1 5 Min 119 77 196 22 Sec

D

4:1 10 Min 119 62 181 30 Sec