Field of the Invention

This invention relates to an insulation product which can serve basically as a thermal and/or acoustic insulation with concomitant properties such as resistance to fire, mould, fungus and bacterial growth control etc., when installed in or adjacent to walls, floors and ceilings of buildings, containers and other space enclosures.

Background of the Invention

The main components of building insulations usually belong to one of two groups i.e. mineral materials and organic ones. Glass fiber is a common mineral insulating material, usually produced in the form of batts or sheets or used as a loose fill. In the last case, although not as detrimental to human health as asbestos fiber (also a mineral material), glass fiber tends to emit dust and minute particles during application.

The second group, organic insulations, in addition to foams includes various cellulosic fibrous and non-fibrous materials e.g. wood pulp, cotton, straw, bagasse, wood flour, hemp, rayon and the like. Proposals exist for cellulosic fiber insulation (CFI) manufactured from recycled newsprint. In Canada, the require¬ ments for the CFI insulation are specified in the CGSB standard 51-GP-60M.

In order to increase the fire resistance of loose-fill cellulosic fiber insulation, various chemicals are added thereto during the preparation or applica¬ tion stages. Additives to stabilize the insulation i.e. to prevent or reduce its settling are also employed.

Loose-fill mineral fiber insulation (MFI), particularly manufactured with molten glass, basalt or slag wool fibers, offers an excellent fire resistance and much smaller settlement than cellulosic insulation.

In recent years, there has been a tendency to reduce the density of loose-fill insulations, both mineral and cellulosic ones. For example, recent advances in the fiberization (fluffing) techniques such as one introduced by Advanced Fibre Technology Inc. reduced the density of blown CFI to as little as

21 kilograms per cubic meter (1.3 pounds per cubic foot). On the MFI side, changes in the fibre manufacturing and the installation machinery caused the density of loose-fill insulations to drop to as little as 9 kg/cu.m. (0.56 lb/cu.ft).

These changes have led to the reduction of field performance of the building insulation materials. It has been evidenced recently, for example, that a certain type of mineral fiber loose-fill material can exhibit a thermal performance, after installation, 30 percent lower than anticipated on the basis of laboratory testing.

It is well recognized in the art that the choice of an insulation, particularly thermal one, is a compromise between its weight, fire resistance, performance and price.

An alternative to either the MFI or CFI loose fill is a wet spray system. Adding water and adhesive will reduce dust and may to some extent reduce the settlement of the CFI insulation. Adding water may, however, intro¬ duce other problems for the systems applied in the cold climates.

A positive development in the loose-fill and spray CFI and MFI products was the introduction in recent years of the Blown In Blanket System (BIBS) such as described in Canadian Patent 1,260,667 issued Sept. 26, 1989 to Sperber. In this system, fibrous insulation is installed behind a plastic netting (mesh) permitting unrestricted air outflow from the cavity while containing the blown-in material in a confined space.

US Patent 3,902,913 to Helser et al describes hydrous calcium silicate insulation products - relatively heavy, solid molded blocks - which com prise 60-95 % hydrous calcium silicate, 0-20 % fillers, 1-20 % organic fibers (bleached wood pulp) and 0.1-10 % glass fibers.

US Patents 4,543,158 and 4,513,045 to Bondoc et al describe a sheet type felt comprising 5-20 % glass fibers, 40-80 % cellulose fibers, binder and asphalt. The felt may be used as roofing underlayment.

Various other types of insulation products are described in US patents Nos 3,379,608 (Roberts), 4,024,014 and 4,072,558 (Akerson), and 3,321,171 (Gorka et al). A perlite-based acoustic board comprising volcanic glass (45-75%), mineral fibers and nongelatinous cellulosic fibers is disclosed in US Patent 3,952,830 to Oshida et al.

While these references describe insulation products comprising, in combination, certain mineral fibers and cellulosic fibers, these products are not intended as light-weight insulation suitable to be blown in into house wall or attic enclosures.

Accordingly, there is still a need for a bonded fibrous lightweight insulation that could be used for floors, walls and ceilings of buildings, containers and other space enclosures and applied mainly by blowing. To meet the latter requirement, the insulation should exhibit a relatively easy flow through the blowing equipment

Summary of the Invention

It has been found now that the flowability of a fibrous mixture depends on the quality of the surface of the fibers, or at least some of the fibers

constituting the mixture. This finding has been combined with the observation that certain wood pulps (e.g. Kraft pulp) consist of fibers having a rather rough appearance (splinters, nodules, etc.), while certain other pulps, notably the thermal- mechanical pulp (TMP) and the chemical-thermal-mechanical pulp (CTMP) contain substantially smooth fibers.

According to one aspect of the invention, there is provided a method of manufacturing an insulation product, the method comprising: 1) providing a mixture comprising at least about 40 wt. % fibrous cellulosic pulp having predominantly smooth fibers, a filler, a bonding agent and optio¬ nally a fire retarding agent,

2) reducing the density of the mixture to about 15-45 kg/cu.m, and

3) bringing the moisture content of the mixture to a level sufficient to achieve at least a partial bonding of the mixture.

It is important that at least about 10% by weight of the total filler is a fibrous material, either inorganic, synthetic or an organic one, the balance being a non-fibrous particulate material.

Preferably, the fibrous wood pulp is either CTMP or TMP. These pulps have only been produced for a few years and have not been considered for insulation purposes. A microscopic examination of these pulps reveals that the surface of the fibers is very smooth compared to such cellulosic materials as Kraft pulp or recycled newsprint.

Tests have shown that a lightweight building insulation made with

CTMP or TMP in the ranges as specified herein, exhibits a markedly better

flowability in blown-in applications than the glass fiber or other prior art fibrous materials.

It is reasonable to expect any other fibrous cellulosic smooth-fiber cellulosic material beside CTMP or TMP to perform in a similar manner as these two pulps.

Examples of the fibrous fillers are, for inorganic fibers: glass, basalt, slag, slagstone fibers; for synthetic fibers: acrylic (PMMA), carbon, polypropylene fibers; for organic fibers: recycled newsprint and other materials.

Exemplary non-fibrous fillers include: amorphous silica, kaolin, fly- ash, recycled shredded rubber (e.g. tires) and carbon black powder with diameter of about 3-30 microns.

Preferably, the pulp is treated with a fire retarding agent, known in the art, while moist. Subsequently, it may be fiberized (fluffed) and mixed with the filler and a bonding agent. The filler, at least the fibrous part thereof, may also be fiberized before being mixed with the cellulosic pulp component.

As used throughout the specification, fire retarding properties denote: at least partial resistance to fire smouldering, reduction of flame spread when forcefully ignited, fire extinguishing when fire source is removed.

Tests conducted to validate the invention have indicated that an effective insulating material can be obtained in the following range of the compo¬ nent content: 40-97 % cellulosic pulp (CTMP or TMP), 1-50 % filler, 1-5% bonding agent and 1-10 % fire retarding agent. The above percentages are by weight based on the dry weight of the mixture.

It has been found that the performance of the insulation of the invention depends on the degree of fiberization of the cellulosic material. Com¬ pared to a hammer mill technology, it is advantageous to fiberize the pulp compo nent (and preferably, also the fibrous filler) using rotational fiberization as described hereinbelow.

According to another aspect of the invention, there is provided an insulation product comprising, on a dry weight basis, at least 40 wt. % cellulosic pulp having predominantly smooth fibers, a filler, a bonding agent and optionally a fire retarding agent. Preferably, the material comprises about 40-97 wt. % pulp, 1-50 wt. % filler, 1-5 wt. % bonding agent and 1-10 wt. % fire retardant.

The material is preferably admixed with an inert liquid compatible with the bonding agent, practically water, shortly before application. The amount of the resulting moisture in the material is adapted so as to achieve at least a partial bonding of the material by reaction of the bonding agent with the water. The actual final water content will depend on a choice and content of the compo¬ nents of the product of the invention.

Before application, the density of the material is preferably reduced, in order to provide a lightweight insulation, to about 15-45 kg/cu.m. It will be appreciated, however, that the invention also encompasses the product before the density reduction.

Brief Description of the Drawing .

In the drawing, the single figure represents a graph illustrating the thermal performance, in terms of thermal resistivity per inch, of the insulation of the invention as compared to prior art insulating materials.

Detailed Description of the Invention

In tests conducted to validate the invention, the pulp (CTMP or TMP) was obtained from a paper mill as a wet substance, usually containing about

40-50 % of solid material by weight. A fire retarding agent, or agents, was added either to the wet pulp during the pulp manufacturing process, or to the relatively dry mixture of the pulp with the filler during the insulation final preparation stage, as described below. Beside a fire retardant, it is known to 'add to a building insulation other chemicals for one or more of the following functions: to control mould, fungi and bacterial growth; to balance pH in order to reduce the risk of corrosion; to reduce fiber swelling and shrinking. A list of acceptable fire retard¬ ing agents and the additional chemicals includes, among others, borax, boric acid, aluminum sulphate, alumina, calcium sulphate, dicalcium hydrogen phosphate, bismuth(II) chloride, urea, sodium carbonate, sodium silicate, tin(II) chloride.

These agents may be added singly or in combination depending on the desired properties of the final insulation.

The choice of a filler, both fibrous and non-fibrous one, is dictated by a requirement that the infrared opacity factor (extinction coefficient for long¬ wave thermal radiation) of the filler contribute to an increased thermal perform¬ ance of the insulation by reducing the radiative heat transfer through the insula¬ tion, and that its specific surface is large enough for bonding into the multiphase fibrous system of the insulation product of the invention.

Water is a necessary additive to the pulp/filler/bonding agent mixture to achieve a bonding, or partial bonding, of the final product when blown in, or sprayed, in the site. The pulp, as mentioned above, usually carries certain amount of water, but it is usually necessary to increase the water content to a sufficient limit for bonding to take place. However, the amount of free water in the final product must be limited so that the insulation's thermal (or acoustic)

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performance is not impaired. Therefore, it is recommended to adjust the amount of water in the product before installation so that the water forms an integral part of the insulation due to physical and chemical reactions with the bonding agent and other components of the insulation. Physical bonding may be achieved by limited admixture to the insulation of calcinated gypsum or cement powder. Chemical binding of water may be effected by the use of e.g. isocyanurates.

Bonding agents suitable for the purposes of the invention are, for instance, polyvinyl acrylate and latex binder.

The pulp is fiberized either before being mixed with the filler or afterwards. Preferably, both the pulp and the fibrous filler are fiberized (fluffed) and admixed with chemicals before being mixed together in a cyclone for a substantially uniform distribution of the components throughout the mixture. The mixture can then be stored in bags and carried to the site where final fiberization and water addition takes place.

The following examples, as part of the testing program, serve to illustrate the invention in more detail.

Example 1

CTMP pulp with freeness of approximately 500, was made from spruce and partially dewatered to moisture content of about 8%. It was then admixed with about 9 % by weight (on a dry basis) of each borax and boric acid and then fiberized using a modified commercial rotational fiberizing equipment. The glass fiber material used had fibers in the length range of 3-6 mm. After fiberization, 90 part by weight of the treated pulp was mixed in a cyclone with 10 parts by weight of glass fiber which was also prefiberized using a commercial blowing machine. The mixture, without the addition of a bonding agent, was then packed in bags and transported to a set-up which comprised a blowing machine equipped with a positive displacement blower and an air lock but no shredder nor

agitator. An additional rotational fiberizer was disposed in line of the flow of the material (a cylinder with spirally disposed sharp protrusions which force rotational movement and impact fiberization of the material). The fiberized mixture was then packed to predetermined densities using test frames (600x600x150 mm). The densities were:18, 21, 24, 28, 44 kg/cu.m. Thermal resistance of the respective insulations in relation to their densities is shown in the drawing (points marked 1). It can be seen that despite this broad density span, thermal resistance of this product varies little.

Example 2

** In this example, all the steps were identical as in Example 1 except a different treatment after the blowing machine set-up. In this example, the mixture was then sprayed with an equivalent amount (1:1 by weight) of a mixture of water (90%) and a commercial latex adhesive (10%). The insulation material was fiberized to a density of about 17 kg/cu.m. Thermal resistivity of the insula¬ tion was tested after the material was oven-dried, and it was found to be slightly better (see point 2 in the graph) than that of the material of Example 1.

Example 3

CTMP was mixed with a filler (90:10 wt. %) consisting of rock modified slag wool having relatively short fibers (1-2 mm). The moisture content of CTMP was the same as in Examples 1 and 2. The insulation was prepared using the same equipment as in Example 2 (fiberization with a conventional blowing machine and spraying). The final density of the material was about 32 kg/cu.m. The thermal performance of the material (point 3) was similar to that of material of Example 1 at comparable density.

Example 4a Example 4a is identical as example 1 except that CTMP was mixed with only 1 wt. % of glass fiber. The density of the material was about 15 kg/cu.m. The thermal resistivity is shown in the graph (point 4a).

Example 4b

In this example, the amount of the filler, rock modified slag wool having fibers in the length range of 3 - 6 mm, was 50 wt. % (50 wt. % pulp). The pulp selected (CTMP) had a relatively low freeness of approximately 350. The preparation of the insulation and the apparatus used were as in the example 4a. The density and thermal performance of the material are indicated in the graph (point 4b).

Example 5

Conventional fibrous insulations were tested for their thermal resistivity at comparable densities. The thermal properties are displayed in the graph as follows: point 5 - GFI 1 (glass fiber insulation), point 6 - GFI 2, point 7 - a low density cellulosic fiber insulation (CFI) manufactured of recycled newsprint, at a density of 25 kg/cu.m., and point 8 - a standard cellulosic fiber insulation with a density of about 43 kg/cu.m.

Conclusions

The comparison of product of Example 2 with that of Example 1 indicates that the fiberization of the product is not impaired by the spraying with adhesive/ water.

An insulation of the invention (example 4a) exhibits a better thermal performance than each of the used components. It should be noted that the mineral fiber used in the example 4b is one of the best commercially available in North America slag/rock melt with long fibers. This mineral fiber, not suitable by itself for pneumatically applied loose fills (due to fiber breakage) may be successfully applied for the production of the insulation of the invention.

It is evident, when analyzing the results of examples 4a and 4b, that the mixing in the fiberized condition of partly wet cellulosic fibers with inorganic

fibers results in a fiber matrix with improved thermal properties. It appears also that the degree of fiber refining (fiberizing) may have a larger effect on the thermal performance of the product than variation in performance of one of the fibrous materials used for the multifiber system, or even varying the fraction of the second fiber (filler) in the mixture between 1 and 50% of the total fiber.

It can be seen from the graph that the insulation of the invention (points l,2,4a,4b) has better thermal resistance than glass fiber insulation (points 5 and 6). It has somewhat lower thermal resistance than CFI (points 7 and 8), but the density of the insulation of the invention is clearly lower than that of the cellulosic fiber insulation.

Referring to the graph, the field marked by a triangle is of particu- lar interest because of relatively low density and good thermal performance of the insulation.

The above results indicate that fiberization (refining) of the fibrous mixture can be controlled to maintain high thermal resistance for the density range 15-22 kg/cu.m. while at the same time 20 to 30 % of the high-performance fibrous mix can be replaced with lower quality fillers or fibers e.g. derived from recycled substances. This may be of advantage when designing fire-protective and sound absorbing products based on the present invention.

Regarding the sequence of the manufacturing process, it should be emphasized that the process may take place partially at a plant, where the mixture is partly fiberized, admixed with some chemicals and bagged, and partly at the installation site where the final fiberization and admixture of water (and a bonding agent) may be effected. Alternatively, all the steps may take place at the site.

SUBSTITUTE SHEET