This invention relates,to insulation material and particularly to laminated insulation material. The

production of effective insulation materials is an

important problem facing all countries today and this is

becoming more important as fuel prices continue to rise.

For example, in the average detached British home, in

excess of three quarters of heating energy is lost via

walls, windows, floor and roof spaces .and, of this loss,

up to twenty five percent is lost through singly glazed

windows. It is, therefore, of utmost importance to

conserve heat energy.

Materials having metallised or metallic surfaces can be used for insulation purposes in that they have a high reflectivity and reflect radiant heat back to a hot

source. However, when a metallic surface is positioned to face away from a hot source, it reduces the heat radiated from it because the metallic surface possesses

low emissivity, that is, a poor ability to radiate heat.

This is demonstrated by the fact that an enclosed air

cavity is at least twice as effective at reducing heat

loss when its boundary surfaces possess low emissivity,

than if they had high emissivity.

The insulating effectiveness of a material is its ability to resist heat flow - known as its thermal resistance

2 and measured in units of m k/w. For example, the thermal

resistance of an unventilated air space of 25mm width and

2 when the heat flow is horizontal or upwards, is 0.18 m k/w

2 with high emissivity boundary surfaces, and 0.35 m k/w

with low emissivity boundary surfaces. When the heat flow

- is downwards, the thermal resistance of the same air space

2 is 0.22 k/w with high emissivity boundary surfaces,

2 compared with 1.06 m k/w with low emissivity boundary

surfaces, that is, nearly 5 times as effective.

Since most building materials possess a high emissivity (G.90-0.95) .and since radiation normally accounts for

about two thirds of the heat transfer, we have found that building materials having metallised or metallic surfaces can be employed to substantially reduce, if not eliminate this radiation thereby producing an insulation material with a very much higher thermal resistance.

There are, however, a number of situations where a

metallic surface is not aesthetically acceptable and

according to one aspect of this invention an insulation

material comprises a substrate having at least a proportion

of the area of one surface thereof coated with first a

layer of a metallic material which is at least partially

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overlaid by a second layer of material which masks the

overlaid metallic material without substantially reducing

the insulative effect of the metallic material.

Preferably, the whole of one major surface of the substrate

is wholly overlaid by the metallic material and the metallic material is'wholly overlaid by the said second

layer. If desired, however, the second layer may be

applied to the first and metallic layer in the form of a

pattern by, for example, spraying, screen printing, use

of transfers etc. Also, according to requirements, a

mixture of the materials used for the metallic material and the material of the second layer may be applied to

the substrate separately or together by spraying or -

otherwise, thereby producing a speckled or other appearance.

The substrate may be rigid-or flexible or structural or non-structural. A flexible material in accordance with the present invention is particularly suitable for use in the manufacture of roller blinds.

In the case of rigid and structural substrates any

conventional building or engineering material may be

used. In the case of flexible substrates, the substrate

material may be a woven or non-wov-en fabric, felt or film

made from natural or synthetic material or a mixture of u

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natural and synthetic materials. The metallic material may

itself be in the form of a laminate comprising a base layer

of a plastics material,, eg. a polyester film or non-plastics material, eg. paper, coated on one or both major surfaces

with a layer of reflective material. The reflective

material may be obtained by aluminising the base layer.

In the United Kingdom, BS5867 Part IIA 1980 is the British Standard which sets out the fire retardant requirements applicable, inter alia, to the manufacture of roller-blinds

made from or containing fabric materials. Where the present

invention is applied in the manufacture of a material having

a flexible substrate and suit-able for use in the manufacture

of roller or other blinds or curtains, we have found that it

is only necessary to treat the substrate with a fire

retardant materials may be used provided such materials are

non-hygroscopic. We prefer to use a polyvinylidene chloride

•antimony oxide, deca-bromide phenyl oxide, a__r_ιonium phosphate composition as the retardant material. On ignition of a

fabric treated with this preferred fire retardant material, an endothermic reaction is created producing copious quantities of antimony halide to form an effective oxygen

barrier thereby effectively smothering any flame. The

endothermic reaction serves to cool localised areas

thereby reducing any risk of spontaneous ignition of

the material of the invention.

The preferred fire retardant material may be applied to

the material of the invention by spraying, dipping or

other known techniques.. Moreover, as indicated we

have found that it is only necessary to treat the

substrate as opposed to the finished materials, with a

fire retardant material.

The layers constituting a flexible insulation material in accordance with the invention may be affixed to adjacent layers using a thermoplastic dry film or a wet coating adhesive.

When considering eflectivity in connection with

insulation, it is important to distinguish between

the reflection of visible light and the reflection

of long wavelength infra-red 'radiation. For example,

the silvered surface on the back of a mirror reflects

both forms of light but, because glass is a poor transmitter of longwave infra-red radiation, the heat

reflecting properties of a mirror surface are no better •than a coating of black paint. On the other hand,

the material we use for the said, second layer

referably transmits infra-red radiation at the

wavelengths connected with the heat radiation from a

source at room temperature (approximately 10 micron) but

does not transmit the wavelengths associated with visible

light (0.4 to 0.7 micron).

Thus, the laminate reflects heat whilst the overlaid metal

is masked from view. •

Our experiments with infra-red transmitting layers

included use of lacquer systems with reflectivities in the range 15-90% and, when applied to an aluminium metallic layer which had been vacuum deposited on a substrate made from plastic film, good results were obtained.

This demonstrated the relative absorbtion for the lacquer

system compared with the reflectance for a bare aluminium layer of 95%.

Clear, dyed and pigmented lacquers were evaluated and a

pigmented polyamide system applied to the metallic

material was found to give a good combination of heat

reflectance and appearance. These varied with pigment

types and Coating weights and a 2 gram per square metre

layer of a buff/fawn pigmented polyamide lacquer produced

a reflectance approximately 70%. The coating weight may be varied according to the use and desired location of

use of the insulation material but we have found satisfac¬

tory results can be obtained using up to 20 grams per

square metre of the second and lacquer layer.

This was considered to give adequate heat saving and an

excellent appearance. ,

The second layer substantially maintains an infra-red

transmitting gap on the face of the metal surface at all

times, thus ensuring-a radiafaion-barrier even in the

absence of an air space. The second layer also protects the metallic surface from the environment. Whereas an

uncovered or unprotected metallic surface would most

probably soon deteriorate, we have found that the second

layer withstood extreme temperatures, and light intensity

when subjected to accelerated ageing in a weatherometer.

A laminated insulation material in accordance with the present invention has many applications in buildings as an effective insulation material.

The metal layer may be applied directly or indirectly on

to a plastics film or paper, or any other suitable sub¬

strate material to which a metal could be fixed or which

can be metallised. Where the metal layer is applied to a

flexible substrate such as plastics film or paper, the so

formed flexible composite could be used on its own, in conjunction with air spaces, or laminated to other

materials such as a fibrous -quilt, or other insulation

materials. Such materials could be used in many places

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in a building, eg. in the roof, loft, floor, wall cavity,

as wall covering or window covering. Further, the flexible composite may be incorporated in an article of clothing, eg. an anorak or a survival suit. Use of the material in

a building is extremely important because thermal photo¬ graphy tests show that the window of a building is one of,

if not the most concentrated area of heat loss in a

building. In a domestic building for example, it accounts

for 25% of the total heat lost from an uninsulated house,

and as much as 40% of the loss from a house insulated to

conventional present day standards.

The use of laminated insulation material according to the

invention and in the form of curtains or blinds provides

an energy saving device for windows, which not only considerably reduces heat losses from the house, but also reduces solar heat gains dramatically. In certain areas in the world, it is more important to reduce solar heat

gains than heat losses, to minimise the input of cooling energy, that is, when air conditioning a building. In

use, the second layer is disposed to face the window and, therefore, reflects back the solar rays normally

transmitted by the window. Our experiments show the

ability of the material of the second layer to reflect

solar rays results in a reduction of solar heat gain

through windows by as much as 80%. Further, the

insulation material of the invention also reduces heat

losses by its inability to radiate heat out to a cold

window due to its low emissivity. When combined with an

air space between the window and coated metal; a very

effective insulating-medium results.

This air space can be achieved by a roller-blind maintain¬ ing a gap between the insulation material (second layer

facing the window) and the window glass. In the case of

a window blind, the metal layer can be laminated to a fabric and used in a conventional roller-blind and

disposed to maintain an optimum air space of 20 mm, so as

to minimise conduction and convection by, for example,

side guides. Such a device reduces the heat lost through

a single pane of glass by nearly 60%. The ability of a material to transmit heat is given by its thermal

2 transmission (U) value (units - w/m k). The U-value for single glazing depends on its tjηpe, thickness, orientation,

2 exposure etc., but is commonly 5.6 w/m k. The U-value for the same window covered with a device as described above

is 2.3 w/m k.

The heat saving thus compares favourably with heat savings achieved with the conventional insulating medium; double

glazing, which commonly has a U-value of 2.8 w/mH .

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Where the blind is used in conjunction with double glazing

2 a U-value of -1.6 w/m k could be achieved thus representing

a saving of over 70%.

It will, therefore, be appreciated that a blind made from

an insulation material according to the invention will

help to control the in-the-room temperature all the year

round. In summer, it should be pulled down sufficiently

to block out direct sunlight yet allowing natural light to enter the building. In winter, the blind should be fully drawn at night to minimise major heat lossess and raised in the day to allow the sun to warm up the building.

A blind incorporating the laminated insulation material

* of the invention, therefore, offers a cost effective

insulation medium ^" for.all climates whilst enhancing the

appearance of a building and the decor of a room.

Although reference has been made to the use of roller-

blinds the insulation material of the invention may be

used as the slats or applied to the slats of Venetian and

other slatted blinds. Furthermore, sheets of the laminated

insulation material may be suspended in the cavaties of walls during building. A further use of such material is

as backing materials for transparent solar heating panels so that the heating medium, usually a liquid, receives

not only direct solar heat but also reflected solar heat.