Spray-applied cellulose insulation and method

Abstract

A spray-on cellulose insulation and method of application is described herein. The insulation comprises cellulose and an adhesive having gelling properties during application, preferably polyvinyl alcohol. The cellulose includes an additive that triggers gelling of the adhesive upon application to the cellulose. The cellulose preferably also includes a crosslinker for the adhesive. The additive and the crosslinker may be the same, which means the crosslinker is sufficiently alkaline to also trigger the gelling of the adhesive upon application of the adhesive to the cellulose. The gelling of the adhesive allows a reduction in the level of moisture added to the cellulose fibres to below 20%, resulting in an insulation with rapid drying times, reduced risk for fungal growth, lower applied densities and a total moisture content below 30% on an oven dry basis.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to building insulation. More particularly, the present invention relates to spray-applied fibre based insulation, most specifically spray-applied cellulose fibre insulation. BACKGROUND OF THE INVENTION [0002] Sprayed cellulose building insulation is generally made from recycled paper or paperboard stock modified with chemical additives. It can be applied to open surfaces or cavities that will be enclosed later. Cellulose insulation is an alternative to commonly used fibreglass insulation in the form of batts or loose fill. Because of the loose nature of the insulation material, sprayed cellulose fibre insulation can be applied to a wide range of areas, including attics, walls, floors or any other voids or hard-to-reach crevices where batt insulation is not easily applied. It forms a uniform covering throughout the cavity and forms a superior air seal around electrical boxes, wiring, pipes and framing members. To r...

AI Technical Summary

Benefits of technology

[0031] Advantageously, the reduced added moisture significantly reduces and potentially obviates drying time, thus allowing construction crews to complete dry wall and related structural tasks with little or no delay after application of the insulation. It is a further advantage of the present invention to provide a reduced-moisture cellulose fibre insulation which nevertheless has sufficient wet strength to remain in a wall cavity during and after application. By keeping the total moisture content on an oven dry weight basis below 30%, fungal growth in raw wood materials surrounding the cellulose insulation is retarded and by keeping the total moisture below 25%, fungal growth is virtually eliminated. It is still a further advantage of the present invention to provide a cellulose fibre insulation in which the thermal degradation period is reduced via a reduction in the amount of time required for the insulation to dry down to ambient conditions. Advantageously, reducing the total added water does not compromise the integrity of the insulation as long as cellulose insulation is applied with an adhesive / additive combination which provides a gelling of the adhesive upon mixture with the additive. It is this gelling of the adhesive upon application, which is believed to provide additional wet strength to the insulation upon application, thereby allowing a reduction in added moisture previously believed impossible. Adhesives / additive combinations applicable for use in the present application include any known aqueous adhesives which are capable of generating a wet gel and their respective gel triggering compounds (additives).

[0032] Prior to spray application, the cellulose fibres are treated with the additive by either admixing the additive in a granular or liquid form with the fibres, or by pounding or spraying it into the cellulose fibres in a fibre mill. When the adhesive used is or contains PVOH, the additive is an alkaline compound used in a sufficient amount to trigger gelling of the PVOH upon admixture therewith. Additives preferred for use in combination with PVOH are alkaline additives having a pH above 7.0, most preferably above 8.0. The alkaline additive is used in an amount sufficient to trigger gelling of the adhesive upon application of the adhesive to the treated cellulose fibres. The cellulose fibres can also be treated for use with PVOH based adhesive with a crosslinker. Most preferably, the cellulose fibres are treated with a crosslinker which is sufficiently alkaline in solution to triggers gelling of the adhesive upon contact with the treated fibres. Examples are ammonium pentaborate, ammonium biborate or the alkaline earth metal borates. Crosslinkers which are not or only slightly alkaline can also be used when combined with a sufficient amount of an alkaline additive to render the mixture alkaline in solution. Mixtures of acidic crosslinkers with alkaline additives in sufficient amount to render the mixture alkaline in solution are also possible. The alkaline compound for use in admixture with the crosslinker is selected to be storage stable and to be compatible with the cellulose fibres and the adhesive to be used. An exemplary acidic mixture of crosslinker and alkaline compound is boric acid and sodium hydroxide in which the sodium hydroxide is added to the resulting mixture in sufficient quantity to achieve alkalinity. Other alkaline compounds which may be used are alkali earth metal oxides, bicarbonates; carbonates or organic base.

[0033] The cellulose fibres are preferably admixed with a sufficient amount of fire retardant to render the insulation compliant with applicable building regulations, especially regulations regarding flammability and smoldering resistance. A fire retardant typically used in the prior art is boric acid. The cellulose fibres are treated prior to being added to a hopper used in applying the treated cellulose to the surface being insulated.

[0034] Gelling testing was performed with exemplary combinations of adhesive (PVOH containing) and alkaline additive and the results are shown in Table 1. TABLE 1ExperimentAdhesiveCellulose AdditiveResultControl4 parts1 part Boric AcidNo gelling4% polyvinylalcohol14 parts1 part Boric Acid +Gelling4% polyvinylSodium hydroxide toalcoholraise pH to >7.024 parts1 part Boric Acid +Gelling4% polyvinylPotassium hydroxide toalcoholraise pH to >7.034 parts1 part 4% ammoniumGelling4% polyvinylpentaborate (pH 7.8)alcohol44 parts1 part 4% ammoniumGelling4% polyvinylbiborate (pH 8.9)alcohol54 parts1 part 4% sodiumGelling4% polyvinylpentaborate (pH 9.0)alcohol64 parts1 part 4% sodiumGelling4% polyvinylbicarbonate to raisealcoholpH to >7.074 parts1 part 4% boric acid +Gelling4% polyvinylsmall amount of 99%alcohol2-aminoethanol84 parts1 part 4% boric acid +Gelling4% polyvinylsmall amount of 4Nalcoholammonium hydroxide

[0035] According to the present invention, an adhesive is added to the cellulose fibres upon spray-application. In one embodiment, an aqueous adhesive resin comprising 3 parts acetate and 1 part PVOH is used, although any suitable aqueous adhesive capable of gelling may be used. Typically, the adhesive concentration is 1-15% (w / w), preferably 5-10%, with a final dry adhesive content of 0.25-3% (w / w), optionally 1-2% (w / w). The adhesive is added to the cellulose fibres at the moment of spray application to the surface to be insulated. No pre-treatment of the cellulose fibres with adhesive or “cooking” is required.

[0036] In a preferred embodiment of the invention, an alkaline crosslinker is used which functions as the alkaline additive, namely sodium pentaborate. It is added to the cellulose fibres in an amount of 5-15% (w / w), optionally 8-10% (w / w).

Problems solved by technology

Although the potential for gelling of certain adhesives during storage was previously observed as disclosed in the prior art (see U.S. Pat. No. 5,684,068), this effect was considered undesirable and was prevented in the prior art insulation application methods by the addition of an acidic medium to the cellulose fibres.