Lightweight glass fiber insulation

Details Lightweight glass fiber insulation Lightweight glass fiber insulation

1999-05-13

2001-09-25

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S036000, C428S295100, C428S295700, C428S364000, C428S375000, C428S378000

Reexamination Certificate

active

06294491

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a fibrous insulation material and, more specifically, to a lightweight fibrous insulation material especially suited for use as an aircraft insulation that meets or exceeds intertracheal biopersistance and carcinogenic product liability regulations established by the European Union and generally provides better acoustical and thermal performance at any given thickness than prior fibrous insulation products used for such applications, such as the prior art products discussed below.
Fibrous insulation products are available in various densities for use in a variety of different applications. One such product is a glass fiber blanket used to insulate structures which require a high degree of insulation, such as aircraft hulls. For such an application it is important to provide an effective barrier to sound and heat transmission through the aircraft hull while keeping the weight of the insulation product at a minimum to avoid adding unnecessarily to the weight of the aircraft.
In the past fibrous insulation products were used which included glass fibers bonded together to form a blanket having a density ranging from about 0.3 to about 1.5 pounds per cubic foot (pcf). Depending on the dimensions of the space being insulated, either a single blanket or several stacked blankets wrapped and secured within a film, e.g. by sewing or heat sealing, were attached to the fuselage of the aircraft by pins secured to a skin of fuselage. In addition to holding the wrapped insulation in place, the pins prevented the insulation blankets from shifting with respect to each other. However, due to the fragile nature of the insulation, a great many pins were required to satisfactorily hold the blankets in place. For example, it was not uncommon for as many as 10,000 pins to be used in the installation of the insulation in an aircraft fuselage. The use of such a large number of pins in the insulation installation was not only time consuming, but the cost of the pins added significantly to the cost of installation. In addition, the pins compressed the insulation in the areas adjacent the pins thereby reducing the sound and heat insulative properties of the insulation.
While such insulation products performed their insulating functions satisfactorily, other characteristics of these products also proved to be a problem. For example, although the low density lightweight construction of these blankets made these blankets suitable as insulators, the low physical properties of these blankets made these blankets very susceptible to damage while being handled. In particular, the relatively low tensile strengths of these insulation products offered little tear resistance to the stresses encountered by the products during fabrication and installation, especially, in applications where the product were placed under tension by being wrapped about a structure. In addition, the normal handling of these insulation products as individual layers or in the fabrication of multilayered products, frequently tore or otherwise damaged the insulation products due to their relatively fragile nature and the wrapping of these products in a film frequently reduced the insulative properties of the product due to the condensation of water vapor trapped within the wrapped insulation.
The above described insulation products have been replaced by an insulation product which has improved tensile strength without adding significantly to the cost or weight of the product and which has eliminated the condensation problems associated with the above described insulation products. This insulation product (described in U.S. Pat. No. 5,169,700, issued Dec. 8, 1992, hereinafter “the '700 patent”) includes a lightweight fibrous insulation blanket having a density range of 0.2 to 1.5 pcf and a thickness in the range of ⅜ inch to 2 inches; and an air permeable facing sheet bonded to one or both major surfaces of the blanket. The fibers of the blanket are bonded together and the facing sheet or sheets are bonded to the major surface or surfaces of the blanket by a thermosetting binder.
SUMMARY OF THE INVENTION
The insulation product of the present invention, which is also especially suited for use as an aircraft insulation, is an improvement over both of the above described lightweight insulation products. The lightweight insulation product of the present invention possesses the required integrity and tensile strengths without the need for a facing sheet, such as woven or nonwoven organic or inorganic scrim as used in the lightweight insulation of the '700 patent, as well as improved acoustical properties (air flow resistance) and thermal conductivity properties for a given density relative to the fibrous blankets of the '700 patent. The lightweight insulation product of the present invention includes a blanket of randomly oriented entangled glass fibers bonded together by a thermosetting binder (preferably a phenolic binder). The fibers have a mean diameter of about 1+/−0.25 microns. The blanket has a density between about 0.25 and about 1.5 pounds per cubic foot and a thickness between about 0.35 inches and about 2.0 inches. The blanket, exclusive of anything else, has an average machine direction tensile strength of at least 0.6 pounds/inch of blanket width and an average cross machine direction tensile strength of at least 0.3 pounds/inch of blanket length; an airflow resistance between about 300 Rayls and about 1800 Rayls; and a thermal conductivity equal to or less than about 0.32 BTU-in/hr-ft
2
-° F.
In addition to the above, the glass fibers of the blanket have a biodissolution rate in excess of 150 ng/cm
2
/hr. The manufacture and/or subsequent handling of fibrous insulation products may result in the formation of loose fibers which can be inhaled. As it is impractical or impossible to remove such fibers from the body, it is important to make fibrous insulation products from glass fibers having a high degree of biosolubility, i.e. fibers which are rapidly solubilized in biological fluids. The fibers used in the preferred embodiments of the present invention possess such properties and preferably, are made from a glass composition that can be fiberized by a flame attenuation processes and still retain a biodissolution rate in excess of 150 ng/cm
2
/hr.


REFERENCES:
patent: 3853569 (1974-12-01), Laurent et al.
patent: 3919134 (1975-11-01), Higginbottom
patent: 5108957 (1992-04-01), Cohen et al.
patent: 5169700 (1992-12-01), Meier et al.
patent: 5401693 (1995-03-01), Bauer et al.
patent: 5612405 (1997-03-01), Bainbridge et al.
patent: 5658836 (1997-08-01), Rapp et al.
patent: 5945360 (1999-08-01), Harding et al.
patent: 5968648 (1999-10-01), Rapp et al.

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