CA2572587A1 - Insulation process - Google Patents

Abstract

A process for insulating a vehicle comprises providing a vehicle (for example, an automobile, truck, train, boat, ship, or aircraft; preferably, an aircraft) with an insulation system comprising at least one insulation article comprising a plurality of discrete, vacuum-containing cells.

Description

INSULATION PROCESS
STATEMENT OF PRIORITY
This application claims the priority of U.S. Provisional Application No.
60/584,588 filed July 1, 2004, the contents of which are hereby incorporated by reference.
FIELD
This invention relates to processes for providing thermal and/or acoustic shielding to, for example, transportation vehicles such as aircraft.
BACKGROUND
Blankets providing thermal and/or acoustic insulation are used in aircraft and other vehicles to shield passengers from engine and aerodynamic noise and from temperature extremes. One problem with such blankets is moisture uptake. This problem is particularly significant in aircraft, where weight increases due to water entrapment in the blankets can be dramatic.
A commercial airliner at cruising altitude experiences exterior temperatures significantly below freezing, often temperatures as low as -4.0°C. The passengers and crew of the aircraft produce significant amounts of water vapor within the fuselage, and this water vapor tends to condense on cold surfaces presented either on the interior cabin wall, within the insulation in the space between the interior cabin wall and the exterior skin of the aircraft, or on the inside of the exterior skin.
Condensation on the interior cabin wall is undesirable from a passenger comfort aspect. Condensation within the insulation is undesirable because it decreases the efficiency of the insulation and because the added weight from the condensed water increases the cost of operation of the aircraft and decreases its payload capacity.
Condensation on the inside of the exterior skin can cause corrosion of the skin and the various structural members attached thereto, resulting in decreased lifetimes for the various components and in the need for periodic inspections to check for and repair or replace the corroded components. Such inspections in turn require that the insulation system be readily removable.

This condensation problem could be largely eliminated if an optimized insulation system could be used. The most common insulation system in use today comprises bats of fiberglass that are enclosed by water-impermeable membranes. The membranes are in turn provided with small holes to prevent ballooning problems within the walls with the inevitable changes in pressure that occur as an airplane changes altitude.
These fiberglass blankets must be custom made for each aircraft type, and, for each type, many individually different patterns must be used in order to effectively provide insulation to the space between the interior cabin wall and the exterior skin while avoiding interference with the various structural and other assemblies also inside this space. Thus, these thermal blankets are expensive and difficult to install and maintain.
The fiberglass blankets work well when initially installed. However, the necessary holes in the exterior membrane allow water to enter into the blankets. It is estimated that this water can increase the weight of the thermal blanket three fold within a three-year period of typical airline service. Another shortcoming of the fiberglass blankets is that they generally do not effectively address low frequency sounds (for example, frequencies below about 500 Hertz).
The industry has searched for alternative insulation systems to overcome the above-described drawbacks and shortcomings of the conventional fiberglass blankets.
Although such alternative systems (for example, foam insulation) have provided improvements in moisture uptake and retention relative to fiberglass blankets, many of the systems are still costly and/or difficult to install and/or remove. In addition, the systems do not completely eliminate the moisture problem, and they also often require additional, relatively heavy components to be able to address low frequency sounds.
SUMMARY
Thus, we recognize that there is a need for vehicle insulation processes (and, in particular, processes for insulating aircraft) that make use of insulation articles that can be easily manufactured and installed, that provide effective thermal and/or acoustic shielding without significant moisture uptake and/or retention, and that can be easily removed from the vehicle (for example, to enable article repair or replacement and/or vehicle maintenance or repair).

Briefly, in one aspect, this invention provides such a process, which comprises providing a vehicle with an insulation system comprising at least one insulation article comprising a plurality of discrete, vacuum-containing cells. The vehicle can be, for example, an automobile, truck, train, boat, ship, or aircraft (preferably, an aircraft; more preferably, a commercial aircraft; most preferably, a commercial jet that has a passenger capacity of at least about 100).
As used herein, "discrete" means that the cells of the article do not communicate with one another, and thus a plurality of (that is, at least two) independent vacuums exists.
Preferably, the article comprises a matrix material (more preferably, a flexible or semi-rigid matrix material; most preferably, a polymeric film). The cells of the article can be integral to the article (that is, formed by the matrix material), but, preferably, a second material is used to form vacuum elements that can be, for example, enclosed by the matrix material or attached thereto.
It has been discovered that moisture condensation problems can be addressed and substantially eliminated by using vacuum-based insulation. Not only is a vacuum the ultimate insulation material from an acoustic and thermal standpoint (as sound, including low frequency sound, cannot travel through a vacuum, and thermal energy is not transferred through a vacuum by conduction or convection), but vacuum-based insulation also does not require perforations or vents to avoid the ballooning problems associated with pressure/altitude changes.
The insulation articles used in the process of the invention provide effective thermal and acoustic insulation with little or no moisture uptake and/or retention. Since the articles rely upon multiple independent vacuums for their effectiveness, a loss of vacuum in one part of the article (due, for example, to a puncture or tear) does not necessarily destroy the insulation characteristics of the entire article.
Thus, the articles are more durable (and more robust during installation and removal) than articles that comprise a single vacuum. At least some embodiments of the process of the invention therefore meet the need for processes that provide effective thermal and/or acoustic shielding without significant moisture uptake andlor retention problems.
DETAILED DESCRIPTION

Insulation Articles Insulation articles useful in carrying out the process of the invention include those that comprise a plurality of discrete, vacuum-containing cells. The articles comprise at least one material that is capable of holding (preferably, for at least about one year) a vacuum (for example, of about 0.5 atmosphere (3~0 torr) or less) and that does not collapse under the vacuum due to its own inherent rigidity, or due to the assistance of a support structure (or spacer), which can be either separate or integral (for example, a microstructure generated in or on the material itself). Preferably, the articles comprise materials that are relatively light in weight; more preferably, at least some of the materials are flexible, so as to provide articles that are at least somewhat flexible in nature.
Numerous useful configurations can be envisioned.
For example, in one embodiment of the process of the invention, insulation articles comprising vacuum-containing spheres ("spherical vacuum elements") made of a rigid material (for example, glass microspheres) can be utilized. Such articles can be in the form of a panel (for example, a foam panel) comprising the spheres, or, alternatively, the articles can optionally further comprise one or more protective layers or even a protective casing or bag (for example, comprising polymer film) that substantially or even fully encloses the spheres. The layers and/or bag can be either flexible, semi-rigid, or rigid.
Although microspheres can be preferred because of their greater durability and resistance to damage from impact and vibration, larger spheres can also be utilized. If desired, the spheres can be attached to the protective layers) or bag, and/or a binder can be added to the spheres to increase the rigidity of the article and to prevent or reduce sphere movement.
In another embodiment of the process of the invention, somewhat different insulation articles can be utilized. A rigid material (for example, glass, metal, or a rigid polymer) can be used to form multiple vacuum elements (each comprising a vacuum-containing cell) in shapes other than spherical. These vacuum elements can be placed into (and/or attached to) a protective bag (for example, comprising polymer film) or can be supported on, attached to, and/or encased in, for example, one or more protective layers of polymer film to form a vacuum-containing sheet that is somewhat analogous to bubble wrap. The resulting insulation article can be flexible (for example, due to the flexibility of the film extending between vacuum elements) yet still hold a vacuum.

In yet another embodiment of the process of the invention, insulation articles comprising multiple flexible vacuum elements can be utilized. A flexible film (for example, a polymeric film having low gas permeability, a metallized polymer film, a mufti-layer film, or a combination thereof) can be used to form flexible vacuum elements.
The elements can be in the form of sheets that can be stacked or layered to produce an insulation article. Spacers (for example, gas-containing or vacuum-containing microspheres; a stiff, light-weight, nonwoven skeletal structure; or a film microstructure such as a plurality of micro-pins) can be used as film supports to enable formation of the vacuum-containing cell of the vacuum element. Optionally, the articles can further comprise one or more protective layers or even a protective casing or bag (for example, comprising polymer film) that substantially or even fully encloses the flexible vacuum elements. The protective layers and/or bag can be either flexible, semi-rigid, or rigid, and the flexible vacuum elements can optionally be attached thereto.
If desired, the spherical, non-spherical, or flexible vacuum elements can be placed in layers in a staggered manner, so that sound and/or heat must encounter at least one vacuum element (rather than a space or joint between vacuum elements) in attempting to pass through the insulation article.
Other useful insulation articles can be envisioned and can comprise one or more vacuum-containing layers. In addition, other materials and layers conventionally found in insulation blankets can be included. For example, the article can further comprise one or more high-temperature resistant materials (including, for example, materials that are resistant to flame propagation and/or flame penetration), one or more adhesive compositions or films, one or more scrims (for example, woven polymeric fabric), one or more water repellent coatings, one or more intumescent additives or coatings, one or more reflective films (for example, for controlling radiant energy), and one or more polymer films (which can optionally be metallized), as well as flame retardants, antistatic agents, anti-mildew agents, and the like.
The above-described insulation articles can be manufactured by known methods and can further comprise one or more attachment devices for use in attaching the articles to each other and/or to the vehicle. Useful attachment devices include adhesives (for example, pressure-sensitive adhesives or non-tacky adhesives), re-closable fasteners (for example, hook and loop fasteners or dual lock fasteners), mechanical interlocks (for example, tongue and groove, buttons and button holes, snaps, and shaped "puzzle-like"
edges or structures), clips, pins, and the like, and combinations thereof. The attachment devices are preferably an integral part of the article, but separate attachment devices can be utilized, if desired.
The articles can be of any shape and size that facilitates coverage of a vehicle surface. If desired, the shapes can be designed to match the shapes of vehicle surfaces (for example, to form custom-shaped articles) and can be provided with one or more cuts or holes to accommodate surface protrusions, etc. Representative examples of usefully shaped articles include spherical articles and "two-dimensional" panels or sheets or thicker versions thereof (three-dimensional "solids") that are, for example, square (six faces), rectangular (six faces), triangular (five faces), hexagonal (eight faces), octagonal (ten faces), doughnut-shaped, and the like. The particular shape and size of the articles that is chosen for carrying out the process of the invention will vary, depending, for example, upon the size of the vehicle and its surface configurations.
Insulation System and Process The vehicle can be provided with the insulation articles in any desired manner (for example, by bringing the articles in or on the vehicle or one or more of its components, for example, by placement, application, or attachment). Thus, the insulation articles can, for example, be attached to the vehicle andlor to each other to form the insulation system.
This can be accomplished using any attachment device that is capable of use with the materials comprising the insulation articles and with the vehicle surface.
For example, the insulation articles can be coated with a first adhesive that will adhere only to itself and will release when pulled upon. Such an adhesive generally . cannot aggressively bind dirt or other contaminants. A second adhesive can be used to attach the insulation articles to the vehicle surface. Alternatively, mechanical fastening systems can be used to attach the articles to each other, and an adhesive can be used to attach the articles to the vehicle surface.
When the insulation articles are in the form of panels or sheets, they can be laid down in an overlapping manner similar to the manner in which roofing shingles are laid down. Such overlap can reduce thermal and acoustic leakage at the joints between the insulation articles and increase the insulating properties of the system. This approach can facilitate installation in confined spaces and enable desirable thermal and acoustic properties to be achieved in such spaces. For such a system, adhesive can be used on one side of the panels or sheets for attachment both to the vehicle surface and to other panels or sheets. Mechanical fasteners can also be used to hold each sheet to the one below.
In addition to the foregoing methods, numerous other possible methods of providing the vehicle with the articles can be envisioned by the skilled artisan. The insulation process of the invention is particularly useful in insulating aircraft by providing (for example, applying or attaching) the insulation system to an area anywhere between and including (i) the interior surface of the exterior skin of the aircraft and (ii) the exterior surface of the interior compartments of the aircraft (including the underside of the floor of the passenger compartment). If desired, at least one interior panel of the vehicle (for example, an aircraft interior panel) can comprise the insulation article (which can be, for example, attached to the panel or an integral part of the panel). The insulation articles can be designed to be flexible enough to push around irregular shapes on the aircraft surface or can simply be positioned to allow wire penetrations, etc. For insulating the aircraft frame, the insulation articles can be designed to be sufficiently stiff yet elastic to enable them to be snapped into place over the frame. Such insulation articles can insulate the frame and also provide attachment sites for the remainder of the insulation system.
Examples Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.
Example 1 Vehicle Insulation Process Using Insulation Article Comprising Glass Bubbles An insulation article is constructed by first cutting OrcofilmTM AN-54W cover film (a heat-sealable, metallized polyvinyl fluoride film available from Orcon Corporation, Union City, California) into two 1 m2 pieces. Four one meter lengths of wood, 5 mm by 25 mm, are then cut and joined together with wood glue to produce a 1 m2 wood frame, 25 mm thick. One piece of the cover film is then placed on the wooden frame and taped to it using Orcotape~ OT-54W tape (a reinforced, metallized, pressure sensitive polyvinyl fluoride tape available from Orcon Corporation, Union City, California) to seal off one of the two open faces of the frame. The frame is then filled with 3MTM
ScotchliteTM K1 Glass Bubbles (hollow glass microspheres having an internal pressure in the range of 1/3 of an atmosphere, available from 3M Company, St Paul, Minnesota) to a depth of slightly more than 25 mm. The frame with the glass bubbles is vibrated by hand to consolidate their packing volume. A straight edge in the form of a one-meter rule is then run over the exposed surface of the glass bubbles to level them to a depth of 25 mm. The second piece of cover film is then placed over the exposed glass bubbles and the remaining open face of the frame and taped in place as previously described to provide an insulation article. The insulation article is attached to a vehicle by using 3MTM Adhesive Transfer Tape 468MP
(comprising an acrylic type of adhesive, available from 3M Company, St. Paul, Minnesota).
Example 2 Vehicle Insulation Process Using Insulation Article Comprising Glass Bubbles 3MTM ScotchliteTM K1 Glass Bubbles (hollow glass microspheres having an internal pressure in the range of 1/3 of an atmosphere, available from 3M
Company, St Paul, Minnesota) are heat treated under vacuum to further reduce their internal pressure.
This is done by placing the glass bubbles in an ultra high vacuum chamber Model LVC1220-HU (available from LACO Technology Incorporated, Salt Lake City, Utah), reducing the chamber pressure to at least 1x10- Torr, and increasing the temperature to 900°C. After one week under these conditions, to facilitate pressure equalization, the glass bubbles are slowly cooled to room temperature and then returned to atmospheric pressure. The resulting reduced pressure glass bubbles are used to construct an insulation article and to attach it to a vehicle as described in Example 1.
Example 3 Vehicle Insulation Process Using Flexible Insulation Article Comprising Non-spherical Glass Vacuum Elements Individual non-spherical, glass vacuum elements measuring approximately 50 mm long by 30 mm wide by 10 mm thick and having an internal reduced pressure of 1x10-7 Torr are made by means of conventional glass technology. A wall thickness of 0.2 to 2.0 _g_ mm is selected to provide durability without excessive weight. An insulation article is constructed by adhering the vacuum elements in place on a sheet of Mylar~ SBL
heat sealable film (a multilayer, polyester-based film having a metallized coating and heat sealable layers, available from Dupont Teijin FilmsTM, Hopewell, Virginia) using 3MTM
Super 77TM Spray Adhesive (an aerosol spray adhesive available from 3M
Company, St Paul, Minnesota). The heat sealable film has a thickness in the range of 25.4 micrometers to 127 micrometers. The spacing between each of the elements is on the order of 2 to 10 mm, which is sufficient to allow a resulting insulation article comprising 10 mm thick elements to be conformable. A second sheet of Mylar~ SBL heat sealable film is then adhered over the vacuum elements and to the first sheet of film, again using 3MTM Super 77TM Spray Adhesive. The resulting construction is then heat sealed around its edges and between the rows and columns of vacuum elements using a standard heat sealer available from Packco Incorporated, Rocky Mount, Missouri, to provide an insulation article. The insulation article is attached to a vehicle by using 3MTM Adhesive Transfer Tape 468MP
(comprising an acrylic type of adhesive, available from 3M Company, St. Paul, Minnesota).
Example 4 Vehicle Insulation Process Using Flexible Insulation Article Comprising Film Vacuum Elements Having a Foam Core Individual vacuum elements are made by vacuum sealing a core of INSTILL foam (a micro-cellular, open-cell polystyrene foam available from Dow Chemical Company, Midland, Michigan) measuring 50 mm long by 20 mm wide by 10 mm thick within Mylar~ SBL barner film (a multilayer, polyester-based film having a metallized coating and heat sealable layers, available from Dupont Teijin FilmsTM, Hopewell, Virginia). A
vacuum chamber equipped with a thermal sealing means is employed to achieve a vacuum of approximately 0.05 Torr. A desiccant is incorporated into each individual vacuum element. A plurality of the elements is placed on a sheet of Mylar~ SBL
barrier film using 3MTM Super 77TM Spray Adhesive (an aerosol spray adhesive available from Company, St Paul, Minnesota) to hold the elements in position. The spacing between each of the elements is on the order of 2 to 10 mm, which is sufficient to allow a resulting insulation article comprising 10 mm thick elements to be conformable. A second sheet of Mylar~ SBL barrier film is then positioned over the plurality of elements and held in position by using 3MTM Super 77TM Spray Adhesive. The resulting construction is then heat sealed around its edges and between the rows and columns of vacuum elements to provide an insulation article. The insulation article is attached to a vehicle by using 3MTM
Adhesive Transfer Tape 46~MP (comprising an acrylic type of adhesive, available from 3M Company, St. Paul, Minnesota).
Example 5 Vehicle Insulation Process Using Multilayer Flexible Insulation Article A flexible, multilayer insulation article is constructed by laying two of the flexible insulation articles described in Example 4 on top of each other. In order to improve insulation performance, the articles are offset by 10 mm in the width direction and 25 mm in the length direction, so as to be overlapping. The two layers are held together with 3MTM Super 77TM Spray Adhesive (an aerosol spray adhesive available from 3M
Company, St Paul, Minnesota). The resulting two-layer construction is placed on a comparably sized piece of Mylar~ SBL barner film (a multilayer, polyester-based film having a metallized coating and heat sealable layers, available from Dupont Teijin FilmsTM, Hopewell, Virginia) and held in position on the barrier film using 3MTM Super 77TM Spray Adhesive. A second, similarly sized piece of barrier film is then adhered to the top layer of the two-layer construction in a similar manner. The edges of the two pieces of barrier film are then heat-sealed together to provide a multilayer, flexible insulation article. The insulation article is attached to a vehicle by using 3MTM Adhesive Transfer Tape 46~MP (comprising an acrylic type of adhesive, available from 3M
Company, St. Paul, Minnesota).
Example 6 Vehicle Insulation Process Using Insulation Article Comprising Honeycomb Core An insulation article is constructed by cutting a 25 mm thick Plascore~ PN2 Nomex~ honeycomb core (an aramid fiber honeycomb made from DuPont Nomex~
paper and coated or impregnated with a heat resistant phenolic resin, available from Plascore, Zeeland, Michigan) into a 1 m2 section. A 0.5 mm thick sheet of MylarTM PET

(a polyester-based film, available from Dupont Teijin FilmsTM, Hopewell, Virginia) measuring approximately 1 m2 is adhered to each major surface of the core using 3MTM
Super 77TM Spray Adhesive (an aerosol spray adhesive available from 3M
Company, St Paul, Minnesota). A small amount of desiccant is added to the cells of the core. The resulting construction is a one-meter square panel with a plurality of individually sealed cells.
Openings or apertures measuring approximately 0.5 mm in diameter are made into each of the cells through one of the polyester sheets. (Alternatively, one of the polyester sheets is provided with perforations prior to adhering it to the core.) The resulting film-covered core is then vacuum sealed within MylarTM SBL barrier film (a multilayer, polyester-based film having a metallized coating and heat sealable layers, available from Dupont Teijin FilmsTM, Hopewell, Virginia) using a vacuum chamber equipped with a thermal sealing means to achieve a vacuum of approximately 0.05 Torr. The barrier film seals each cell to provide an insulation article comprising a plurality of discrete, vacuum-containing cells. The insulation article is attached to a vehicle by using 3MTM Adhesive Transfer Tape 46SMP (comprising an acrylic type of adhesive, available from 3M
Company, St. Paul, Minnesota).
The referenced descriptions contained in the patents, patent documents, and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. Various unforeseeable modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only, with the scope of the invention intended to be limited only by the claims set forth herein as follows:

Claims (17)

1. A process comprising providing a vehicle with an insulation system comprising at least one insulation article comprising a plurality of discrete, vacuum-containing cells.

2. The process of Claim 1, wherein said vehicle is selected from the group consisting of automobiles, trucks, trains, boats, ships, and aircraft.

3. The process of Claim 1, wherein said vehicle is an aircraft.

4. The process of Claim 1, wherein said insulation article comprises a plurality of spherical vacuum elements.

5. The process of Claim 4, wherein said spherical vacuum elements are glass microspheres.

6. The process of Claim 4, wherein said insulation article further comprises one or more protective layers or further comprises a protective bag that substantially or fully encloses the spherical vacuum elements.

7. The process of Claim 1, wherein said insulation article comprises a plurality of non-spherical vacuum elements.

8. The process of Claim 7, wherein said non-spherical vacuum elements comprise a material selected from the group consisting of glasses, metals, and polymers.

9. The process of Claim 7, wherein said insulation article further comprises one or more protective layers or further comprises a protective bag that substantially or fully encloses the non-spherical vacuum elements.

10. The process of Claim 1, wherein said insulation article comprises a plurality of flexible vacuum elements.

11. The process of Claim 10, wherein said flexible vacuum elements comprise a material selected from polymer films, metallized polymer films, multi-layer films, and combinations thereof.

12. The process of Claim 10, wherein said insulation article further comprises one or more protective layers or further comprises a protective bag that substantially or fully encloses the flexible vacuum elements.

13. The process of Claim 4, Claim 7, or Claim 10, wherein said vacuum elements are arranged in layers in a staggered manner, so that sound and/or heat must encounter at least one vacuum element in attempting to pass through said insulation article.

14. A process comprising providing an aircraft with an insulation system comprising at least one insulation article comprising a flexible or semi-rigid matrix material and a plurality of discrete, rigid, non-spherical vacuum elements that are formed from a second material.

15. The process of Claim 14, wherein said matrix material is semi-rigid, and wherein at least one interior panel of said aircraft comprises said insulation article.

16. The process of Claim 14, wherein said aircraft is a commercial aircraft.

17. The process of Claim 16, wherein said commercial aircraft is a commercial jet that has a passenger capacity of at least about 100.