WO1987006297A1

WO1987006297A1 - Method for the manufacture of insulating window units

Info

Publication number: WO1987006297A1
Application number: PCT/SE1987/000156
Authority: WO
Inventors: Jan Karlsson; Ingemar Fasth
Original assignee: Barrier Hb
Priority date: 1986-04-11
Filing date: 1987-03-26
Publication date: 1987-10-22
Also published as: DK653587A; SE457367B; DK158103C; DK653587D0; DK158103B; ES2016424A6; SE8601650D0; AU7286787A; SE8601650L

Abstract

A method for the manufacture of insulating window units with glass panes in a spaced relationship. A gas mixture inside the spaces is composed of a selection of gases with the characteristic of having a high absorption capacity for electromagnetic radiation in the wave-length field of 2-20 mum and without a noticeable influence on visible light. The choice is made in such a way that the gases complement one another with regard to the extension of their absorption bands in order to ensure the coverage by these of the wave-length field to the greatest possible extent where the radiation intensity and thus the transport of energy are at their greatest.

Description

Title:

Method for the manufacture of insulating window units.

Technical field:

The present invention relates to a method for the manufacture of insulating window units. The method involves the joining together of at least two glass panes by means of a frame system with the formation of one or more gas-filled spaces between the surfaces of the panes facing one another, the introduction of gas into the space or spaces, and sealing to prevent the exchange of gas with the surroundings by means of the frame system and its attachment to the panes.

Background:

In order to save heating energy, an effort is made to achieve a good thermal insulation capacity in the windows used in buildings. The objective associated with this is for the windows to be provided with an insulating capacity equivalent to the insulating capacity of a normal wall structure. It is not then necessary to limit the area of the window for insulation reasons. By using large window areas it is possible to achieve good utilization of the available daylight for lighting purposes, and also in many cases to achieve a better total energy balance due to the fact that solar energy can be better utilized as a result of increased irradiation by sunlight.

It has long been known that it is possible to improve the insulating capacity of windows by using a number of panes of glass, between which a stationary layer of air is provided. The thicker this layer, the greater the insulating capacity, on condition that the movement of the gas by convection is not too excessive. In order to avoid this phenomenon in the case of thick layers, the space between the outer panes is divided up into a number of spaces by additional panes of glass. This produces a construction which limits conduction and convection, although thermal radiation through the window remains relatively high. In order to reduce this, too, it is known to provide one of the glass surfaces with a metal coating which reflects the thermal radiation back into the building, at the same time as which the metal coating is sufficiently thin to be transparent. In insulating glass units of this kind for windows, it is sufficient to use two coatings, and thus three panes of glass, with a relative spacing of approximately 12 mm. In order to restrict the need for cleaning to only the outer surfaces, units of this kind are usually hermetically sealed during manufacture, so that cleaning of the inner surfaces is unnecessary. These hermetically sealed spaces also permit the spaces between the panes to be filled with a gas other than air, enabling metals such as copper and silver, which are altered by the effect of the air, to be used by filling the space with a rare gas which is inert to the metal coating.

The overall insulating capacity achieved in the case of the window construction described here is so good as to stand comparison with the insulating capacity of the wall, to which must be added the extra energy supplied by the sunlight which is able to radiate in through the pane. Nevertheless, the aforementioned metal coating exhibits undesirable characteristics in certain respects. The first of these which must be mentioned is the weakening of the arriving daylight, resulting in an increased need for artificial lighting. At the same time it imparts a tone and a certain change in colour when looking through the window, to which many individuals react adversely, especially when such . windows are fitted in residential accommodation. There is also a small reduction in the level of extra energy supplied by the sunlight.

As an alternative to metal coatings, the use has accordingly been proposed of layers of gas inside the hermetically sealed spaces, said layers consisting of gases which limit thermal radiation. The existence has, in fact, been established of a number of gases which exhibit restricted transmission in the infrared range, whereas their transmission of visible light and short-wave sunlight remains practically unaffected. It has been established in connection with the invention that in such window units it is possible to achieve a level of insulation against thermal radiation which is almost as good as that of the aforementioned metal-coated surfaces, but-without any effect at all on the visible light.

Technical problem:

Consideration must be given to a large number of simple and compound gases with a large number of characteristics when producing a suitable gas mixture which provides not only full transparency but also, if possible, an optimum insulating capacity with regard to thermal radiation. It is thus necessary to discover a mixture of gases in which each of the individual gases exhibits characteristics such that they can be approved for the intended purpose, and a mixture of gases in which the constituent gases do not produce an adverse effect on one another, and, in order for the desired radiation-suppressing effect to be achieved, gases which complement one another in producing a barrier in the form of a broad and strong absorption barrier against thermal radiation.

The solution:

An advantageous gas mixture for insulating window units may be produced in accordance with the invention by: mixing together at least two, and preferably three gases from a range of gases, each of which exhibits the following characteristics:

a boiling point not above 20°C;

a distinct, high absorption capacity for electromagnetic radiation in the wave-length field of 2-20 μm, and especially in the field of 5-15 μm, within at least one waveband;

compatibility with the other selected gases;

high transparency, without a noticeable influence on visible light;

non-explosive in the mixing proportions which may occur when used in window units,

in conjunction with which the choice shall be made having regard for the relative characteristics of the constituent gases, such that:

- the gases complement one another with regard to the extension of their absorption bands within said wave-length field, in such a way that they complement one another so as to ensure the coverage of the wave-length field to the greatest possible extent; and

- the gases are selected with regard to the positioning of their absorption bands in relation to the intensity of the radiation within the wave-length field in such a way that the coverage by means of the wavebands is arranged primarily so that absorption will take place in those fields in which the radiation intensity and thus the transport of energy are at their greatest.

Advantages:

By producing a gas mixture for the filling with gas of windows of the aforementioned kind in accordance with the invention, a window is obtained with a high insulation capacity and other characteristics which are advantageous in connection with windows.

Brief description of drawings:

Figs. 1 and 2 of the accompanying drawing illustrate in the form of two graphs the bases for the production of a suitable gas mixture.

Best mode of carrying out the invention:

Certain procedural steps must be taken in order to achieve a suitable design of the window unit on the whole and the best possible effect from the gas mixture. Presented first of all are the fundamental requirements for the proposed product, a window unit. These fundamental requirements are as follows:

Product requirements

The window unit shall be capable of being used at least at temperatures of between -20°C and +40°C measured in the gas. It shall be noted in conjunction with this that, when installed, the building in which the window unit is installed will produce a certain amount of temperature equalization in relation to the ambient temperature. The aforementioned temperature range should accordingly be applicable to all such installations in which the use of insulating window units is of interest. The unit shall be capable of being executed in acceptable dimensions, and in essentially the same dimensions which are currently applied as a standard. What this means essentially is that the number of coatings shall be restricted to two, accordingly with a maximum of three panes of glass, and that the relative spacing should be of the order of 12 mm.

The internal gas pressure shall be capable of corresponding to atmospheric pressure, so that window areas of the same size as are currently common can be used with the same thicknesses of glass as are currently encountered.

The absorption of thermal radiation shall be at a high level.

There shall be no noticeable effect on the transmission of visible light.

An increased thermal storage capacity in relation to air-filled or inert gas-filled window units shall be the objective. A t emperature-equalizing effect can be achieved in this way, enabling equalization of the effect on the indoor temperature of a change in the outdoor temperature, for example between night and day. The window unit shall accordingly be capable of acting as a thermal storage unit.

A high degree of thermal inertia shall be the objective, and thus an extended period before a change in temperature on one side of the unit becomes noticeable on the other side. This can be expressed as a time factor, whereas the thermal storage capacity is more of a quantitative factor.

There shall be no harmful effect on the surroundings in the event of the gas being released. Thus, under the conditions under which release can occur, the. gas shall not exhibit a greater degree of toxicity, radioactivity or corrosiveness, and shall not be explosive. This shall apply at the concentrations which can occur in the event of release resulting from breakage of the glass. The gases shall not be explosive in combination and shall not emit a dangerous level of radioactive radiation from the window unit.

Production on an industrial scale shall be possible. The gas shall accordingly be capable of being handled under industrial conditions and shall be available for purchase in sufficient quantities.

On the basis of these product requirements, certain requirements may be imposed on the individual gases which may be used. These are:

Requirements for gases which may be selected

Boiling point not exceeding-20°C.

High absorption capacity for electromagnetic radiation in the wave-length field 2-25 μm, and especially in the field of 5-15 μm. This is applicable to spacings of approximately 12 mm in thickness at atmospheric pressure, including in mixtures containing other gases (limited partial pressure). Compatible when mixed with other gases intended to complement one another (see below for more details).

High transparency, without a noticeable influence on visible Iight.

Low thermal conductivity.

High thermal value (thermal storage capacity).

High viscosity so as to restrict convection.

Non-explosive in the mixing proportions which can occur in the intended application.

Non-toxic in the dilutions which can occur.

Non-corrosive in the dilutions which can occur.

Not capable of emitting dangerous radioactivity in the quantitites which can occur.

Available, or capable of being made available, on an industrial scale.

The next stage is the combination of the gases which are to be used and which have been selected from the available range. There is no individual gas in existence which is capable of producing an optimum effect, or even a particularly advantageous effect. This is attributable primarily to the fact that the thermal radiation absorption ranges of the individual gases consist of one, or usually several, narrow wavebands which cover only quite a small part of the wave-length field of interest for so-called long-wave thermal radiation or infrared radiation. When dealing with such radiation, it is customary to start from so-called black body radiation, that is to say the thermal radiation emitted by an ideal black body. As will be appreciated from Fig. 1, this type of radiation exhibits its greatest intensity, and thus its greatest heat content, at a wave-length of 15-20 μm, and the radiation exhibits considerable intensity within the 10-30 μm range. It is accordingly in these fields that the absorption of the gases is required to provide coverage to the greatest possible extent, and is preferably the field in the direction of the shorter wave-lengths down to 5-6 μm, as will be appreciated from the curve in Fig. 1.

The effect produced by absorption in the form of the braking of the energy flow through the aforementioned radiation increases in proportion to the intensity of the radiation within the waveband in which the gas has its absorption band.

The choice of gas combination is in this way made highly complex. First of all it is necessary to select a number of gases, the absorption bands of which are situated in such a way that they complement one another within the wave-length field of interest. Consideration must also be given to the fact that the absorption bands must be situated in the most advantageous manner possible having regard for the radiation intensity within the wave-length field in question in relation to the absorption capacity of the gas at the various points along the wave-length scale. This gives rise to complicated calculations, in which each gas must be evaluated in respect of its effect on the energy flow, in other words the size and position of its absorption band within the wave-length field, having regard for the effect of absorption. The various gases must accordingly also be combined in such a way as to complement one another. In addition, after having eliminated those gases which are rendered unsuitable by their toxicity, for example, it may then be necessary to take account of the aforementioned factors of viscosity, thermal conductivity and thermal storage capacity. Since thermal energy is transmitted not only by radiation, a gas mixture which appears rather less advantageous from the point of view of radiation may be more advantageous in relation to convection and/or conduction, so that the insulation capacity to prevent the exchange of heat is nevertheless better. In addition, there may be grounds to take account of factors which affect comfort; as mentioned above, temperature equalization over a 24-hour period can be achieved by utilizing the thermal storage capacity and the thermal inertia of the gases. There is accordingly no optimum mixture of gases which is suitable for all conceivable conditions. It is possible to imagine mixtures of gases which have been modified in various ways, for various purposes, such as giving priority to achieving the best possible insulation capacity, or thermal comfort, or perhaps other factors such as increased or reduced dependence on serviceability at low temperatures (variation of the limit of the highest boiling point).

The combination of the gases must accordingly take place in accordance with the following schedule.

The determination of the use-related factors, such as requirements relating to use at a specified minimum temperature or giving priority to the best possible insulation capacity or to certain factors affecting comfort.

The analysis of the effect of the individual gases on thermal transmission, taking the aforementioned account not only of the size of the absorption bands, but also of their position within the wave-length field of the absorption bands.

The combination of the gases so that they complement one another with their absorption bands distributed over the wave-length field of interest.

Amendments to the choice of gases and the relative proportions of the gases, or the addition of gases with specific characteristics, for example the ability to increase viscosity.

It is also necessary to determine the proportions in which the gases are to be present. The relative volumes at which the gases are present determine their partial pressure. A higher pressure produces a greater effect on the energy flow and emphasizes other physical properties. Thus, when determining the proportions, account must also be taken of the capacity of the various gases to influence the energy flow. Absorption is not in a linear relationship to partial pressure, however, and the effect on the absorption of the individual gases within their respective wavebands by reducing the partial pressure through mixing with other gases is relatively low.

When selecting gases which may conceivably be suitable for use on the basis of the criteria applied previously, what has emerged in conjunction with the invention is that the following gases are of interest for use with the intended product:

Primary group:

Freon 12, CI₂CF₂ p r o py l e n e , C H₃ C H : C H₂ Freon 13, CICF₃ p r o py n e , C H₃ C ⋮C H Freon 13B1, BrClF₃ nitrous oxide, N₂O Freon 14, CF₄ sulphur hexaf luoride, SF₆ Freon 22, CICHF₂ ammonia, NH₃ carbon dioxide, CO2

Secondary group:

methane, CH₄ ethylene fluoride, CH₂:CHF ethylene, CH₂:CH₂ propadiene, CH₂:C:CH₂ ethane, CH₃CH₃ cyclopropane, C₃H₆ acetylene, HC⋮HC methyl ether, CH₃OCH₃

The following advantageous combinations emerged from calculations made on the basis of the criteria which had been stipulated in respect of the gas combination:

Gases Proportion (by volume)

I: SF₆, F13, F22 0.4 / 0.2 / 0.4

II: S F₆, F12, F13, F22 0.2 / 0.3 / 0.2 / 0.3

III: CH₃C⋮CH, F12, F13, F22 0.5 / 0.2 / 0.1 / 0.2 IV: SF₆, CH₃C⋮CH, F13, F22 0.2 / 0.5 / 0.1 / 0.2

F12, F13 ... = Freon

These combinations represent examples of advantageous embodiments of the invention when these gas combinations are used for filling insulating glass units. The measured values for the effect on thermal transmission through radiation are expressed below as a percentage value for radiation transmission, in this case the transmission subtracted from 100, which produces an expression for the percentage reduction in the radiation transmission. Also indicated is the k-value frequently used in a structural engineering context, in this case the thermal transmission from one side of the window unit to the other, expressed in W/m² and in °C. This value is identified by (A) in relation to a window unit with two panes of glass and a single 12 mm gap, and by (B) in relation to a window unit with 3 panes of glass and two 12 mm gaps.

I: Reduction in radiation: 26.5% k-value: (A) = 1.93 (B) = 1.38 II: Reduction in radiation: 30.2% k-value: (A) = 1.9 (B) = 1.35 III: Reduction in radiation: 30.1% k-value: (A) = 1.9 (B) = 1.35 IV: Reduction in radiation: 29.8% k-value: (A) = 1.92 (B) = 1.36

Ordinary window unit filled with air Reduction in radiation: approx. 0% k-value: (A) ≈ 3 (B) ≈ 2

The transparency was excellent in all cases, being at least as good as in corresponding air-filled units, and with no noticeable colouring of the light. The thermal conductivity of all the gas mixtures was low, being approximately one half of the thermal conductivity of air and also significantly lower than that of argon. The gas mixtures also exhibit low convection due to the low mobility of the constituent molecules (high viscosity). It was possible, as a general rule, to note a significant increase in the thermal storage capacity and the thermal inertia of the window unit in relation to those filled with air or inert gas. It can be assumed, for example, that the transition of heat from one side of a unit to the other as a result of changes in temperature on one side will be observed after only a few minutes in the case of air-filled units, but after a number of hours in the case of units filled with gas in accordance with the invention. There are no procedures for the measurement of these phenomena, however, and it is accordingly not possible to express them as measured values at the present time. The result should, however, be significantly improved comfort, especially in the case of fluctuating external conditions with regard to temperature and solar radiation.

The method as a whole is implemented in such a way that a window unit with two, three or more panes is produced. This is done in a previously disclosed manner by joining together the required number of panes by means of a frame system which provides a distance between the panes such that the spaces for the gas are formed between them. The sealing of these gas spaces is effected by means of adhesive and sealing compounds which join the frame system to the panes. By the appropriate choice of adhesive and sealing compound it has proved possible by the application of previously disclosed methods to achieve total sealing against water vapour. The molecules of the constituent gases are larger than the water molecules, and total sealing is accordingly also achieved for the proposed gas mixtures. The frame system serves as a support for some kind of moisture-absorbing substance such as silica gel, so that any water which is present will be removed in its entirety from the enclosed gas and the system as a whole.

For the purposes of industrial production it is necessary to perform the joining operation in the surrounding air, with the result that the spaces between the panes are filled with air after joining. This air must then be replaced with the gas mixture. This is done by making holes in the frame system, so that gas can be introduced into each gas space on one side, whilst allowing the enclosed air to escape on the other side. In order to achieve the desired insulating effect, it is essential for at least practically all the air to be replaced by gas.

The fact that a considerably improved insulation capacity is achieved through the absorption of radiation by means of a gas mixture composed in accordance with the invention compared with the previously disclosed gas mixtures used in this context does not exclude the possibility that a further improvement in the radiation-suppressing effect can be achieved by the previously disclosed coating of panes of glass with a reflective layer. A reflective layer of this kind consists of a thin layer of a metal or a metal oxide which is transparent and yet has a certain effect on the visible light. Since a layer of this kind further suppresses the thermal radiation over and above the suppression which is achieved by means of the gas mixture, the result is a combined effect. This combined effect imparts an insulating capacity to a window unit containing not only the gas mixture in accordance with the invention, but also a reflective layer, which insulating capacity is very high and is comparable with what can be achieved by means of walls made of customary building materials and of reasonable thickness.

Claims

Patent CIaims:

1. Method for the manufacture of insulating window units involving the joining together of at least two glass panes by means of a frame system with the formation of one or more gas-filled spaces between the surfaces of the panes facing one another, the introduction of gas into the space or spaces, and sealing to prevent the exchange of gas with the surroundings by means of the frame system and its attachment to the panes, c h a ra c t e r i z e d in that the gas used for introduction between the panes is a mixture, which is produced: - by mixing together at least two, and preferably three gases from a range of gases, each of which exhibits the following characteristics: boiling point not above 20°C; a distinct, high absorption capacity for electromagnetic radiation in the wave-length field of 2-20 μm, and especially in the field of 5-15 μm, within at least one waveband; compatibility with the other selected gases; high transparency, without a noticeable influence on visible light; non-explosive in the mixing proportions which may occur when used in window units, in conjunction with which the choice shall be made having regard for the relative characteristics of the constituent gases, such that:

- the gases complement one another with regard to the extension of their absorption bands within said wave-length field, in such a way that they complement one another so as to ensure the coverage of the wave-length field to the greatest possible extent; and - the gases are selected with regard to the positioning of their absorption bands in relation to the intensity of the radiation within the wave-length field in such a way that the coverage by means of the wave bands is arranged primarily so that absorption will take place in those fields in which the radiation intensity and thus the transport of energy are at their greatest.

2. Method according to Claim 1, c h a r a c t e r i z e d in that the range of gases from which those which are to be included in the mixture are selected is made up of the following gases:

Primary group:

Freon 12, CI₂CF₂ propylene, CH₃CH:CH₂ Freon 13, CICF₃ propyne, CH₃ C⋮CH Freon 13B1, BrClF₃ nitrous oxide, N₂O Freon 14, CF₄ sulphur hexaf luoride, SF₆ Freon 22, CICHF₂ ammonia, NH₃ carbon dioxide, CO₂

Secondary group: methane, CH₄ ethylene fluoride, CH₂:CHF ethylene, CH₂:CH₂ propadiene, CH₂:C:CH₂ ethane, CH₃CH₃ cyclopropane, C₃H₆ acetylene, HC:HC methyl oxide, CH₃OCH₃

3. Method according to Cla'im 2, c h a r a c t e r i z e d in that the gases SF₆, Freon 13 and Freon 22 are selected for the mixture essentially in the proportions 0.4, 0.2 and 0.4 respectively.

4. Method according to Claim 3, c h a r a c t e r i z e d in that the gases SF₆, Freon 12, Freon 13 and Freon 22 are selected for the mixture essentially in the proportions 0.2, 0.3, 0.2 and 0.3 respectively.

5. Method according to Claim 4, c h a r a c t e r i z e d in that the gases CH₃C⋮CH, Freon 12, Freon 13 and Freon 22 are selected for the mixture essentially in the proportions 0.5, 0.2, 0.1 and 0.2 respectively.

6. Method according to Claim 5, c h a r a c t e r i z e d in that the gases SF₆, CH₃C⋮CH, Freon 13 and Freon 22 are selected for the mixture essentially in the proportions 0.2, 0.5, 0.1 and 0.2 respectively.

7. Method according to any of the preceding claims, c h a r a c t e r i z e d in that glass coated with a reflective layer is selected for at least some of the panes.