EP3964618A1

EP3964618A1 - Mineral wool insulation

Info

Publication number: EP3964618A1
Application number: EP21194460.8A
Authority: EP
Inventors: Marko MEGLIC; Anze GRILC
Original assignee: Knauf Insulation SPRL
Current assignee: Knauf Insulation SPRL
Priority date: 2020-09-03
Filing date: 2021-09-02
Publication date: 2022-03-09
Also published as: GB202013888D0

Abstract

The invention relates to an oven, notably a domestic oven, having an oven cavity thermally insulated with a mineral wool insulation, notably a mineral wool insulation substantially free of a binder and/or organic compound(s).

Description

The present invention relates to a mineral wool insulation for thermal and/or acoustic insulation, notably of household appliances or electrical appliances, particularly ovens, with or without a pyrolytic cleaning function, for example microwave ovens with grill function.
Heat generating household appliances, for example ovens, commonly comprise double walls surrounding the oven cavity which define a space filled with insulation material. The insulation material is intended to: reduce loss of energy to the surroundings, thus reducing energy consumption of the appliance; and/or shield elements of the relevant appliances, for example wiring, electrical components and electrical motors, and/or adjacent spaces or furniture from high temperature exposure; and/or reduce noise emission. Mineral wool is often a preferred insulation material for such applications thanks to its thermal insulation properties, its resistance to relatively high temperature exposure, its acoustic attenuation and its good fire resistance. Any organic binders used in the mineral wool product tends to decompose when first subjected to high temperatures and to generate unpleasant or undesired gas emissions; consequently, the insulation mineral fibre material for such applications preferably contains no or only low levels of organic binders. Alternatively, inorganic binders may be used but these tend to result in an insulation material which releases an undesirable level of dust during assembly and/or loses strength or becomes sticky if exposed to humid conditions, for example during transport or storage.
Needled mineral wool felts comprising mineral wool fibres subjected to needling have also been proposed for thermal insulation in household appliances. For example, needled glass fibre mineral wool felts or needled rock fibre mineral wool felts are used for thermally insulating oven cavities, generally being arranged within an insulation cavity which surrounds the oven cavity. But the thermal conductivity of mineral wool felts tends to increase upon needling, and even by decreasing the amount of needling, the thermal conductivity and the energy efficiency of the insulated oven are not as good as required. Furthermore, below a certain amount of needling, the mineral wool insulation is not self-supporting anymore and falls apart, rendering the installation of the felt difficult for the requirements of the industry. Furthermore, in order to facilitate needling, needling aids are often used but also tends to decompose when first subjected to high temperatures and to generate unpleasant or undesired gas emissions.
There is thus a need for an improved mineral wool insulation which provides good thermal insulation, energy efficiency when used in an oven and which generates low level of unpleasant or undesired gas emissions when subjected to high temperature.
One aim of the present invention is to provide an improved mineral wool insulation configured to improve the energy efficiency of an oven and an improved oven which incorporates such a mineral wool insulation. Another aim of the present invention is to provide an insulated oven having improved energy efficiency.
Thus, in accordance with one of its aspects, the present invention provides an oven comprising a mineral wool insulation in accordance with claim 1. Other aspects are defined in other independent claims. The dependent claims define preferred or alternative embodiments. As used herein, the term "consists essentially of" is intended to limit the scope of a definition or claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the so defined or claimed invention. The standards referred therein are those currently in force at the effective date of the present patent application.
The present invention provides a mineral wool insulation which combines a plurality of interconnected advantages:

the mineral wool insulation is binder-free and thus avoids, or greatly reduces, the release of unpleasant off-gases;
the mineral wool insulation comprises unneedled mineral wool fibres, and thus provides a mineral wool insulation having low thermal conductivity; and
the mineral wool insulation has a low density which absorbs less heat generated by the oven, thus providing an oven having lower energy consumption and a better efficient energy labelling.

The binder-free mineral wool insulation is preferably a unitary binder-free mineral wool insulation. The term "unitary mineral wool insulation" as used herein means a mineral wool insulation in which all of the mineral wool of the insulation is sufficiently held together so that the mineral wool insulation can be handled and manipulated as a single unit (as opposed to a collection of two or more freely separable individual pieces of mineral wool). Use of a unitary mineral wool insulation facilitates handling of the mineral wool insulation, for example for placement in an oven or microwave or for assembly with other mineral wool insulations.
According to one embodiment, the invention provides a method of manufacturing mineral wool insulation, comprising i) exposing a mineral wool felt of mineral wool fibres to a temperature of at least 450°C and ii) compressing the mineral wool felt while hot to form the mineral wool insulation.
Whilst not wishing to be bound by theory, it is believed that submitting the mineral wool fibres to a temperature of at least 450°C, particularly for glass wool fibres, is sufficient to slightly soften the external surface of the fibres in order to connect and bond the fibres together but not too high to completely soften or melt the fibres, the temperature being sufficient to increase the level of tangling between fibres when compressed. The combined effect of heat and compressing has been found to provide sufficient integrity to the fibres to provide a self-supporting mineral wool insulation, which can be handled and/or transported and/or assembled in an appliance. Additionally, the heating temperature of at least 450°C facilitates compressing of the mineral wool fibres, and after the step of compressing, the mineral wool insulation substantially retain its compressed thickness and does not recover to the original thickness before compressing.
Particularly when the mineral wool fibres are glass wool fibres, the heating temperature may be between 500°C and 600°C, preferably between 520°C ad 570°C. The skilled person will adapt the temperature based on the mineral wool fibre composition. For example, the temperature required to soften the external surfaces of stone wool fibres will usually be higher than the temperature required for glass wool fibres.
In a preferred embodiment, the mineral wool felt is compressed under a pressure of at least 15kPa and/or less than 35kPa, notably in the range 20-30kPa. This provides sufficient pressure to increase the adhesion and for the entanglement between the fibres, and provide the desired thickness whilst avoiding breakage of the fibres. These ranges of pressure are particularly adapted to compress a mineral wool felt from a thickness in the range 5-20cm to a thickness in the range 15-50mm. During compressing, the thickness of the mineral wool felt may decrease by at least 3 times, by least 5 times, by least 7 times and/or by less than 15 times, by less than 12 times, by less than 10 times with respect of the thickness before compressing.
The compressing of the mineral wool felt may last at least 30 seconds, at least 1 minutes, at least 5 min, at least 10 min and/or less than 20 min, notably less than 15 min. The duration of the compressing may depend on the temperature of the mineral wool fibres during the compressing. Particularly when the mineral wool fibres were exposed to heat before compressing, the compressing may last at least 30 seconds and/or less than 5 minutes. Alternatively, when the mineral wool fibres are heated during the compressing, the compressing may last at least 5 minutes, at least 10 minutes and/or less than 20 minutes.
In one embodiment, the compressing of the mineral wool felt may be performed by heating one or two clamping plates and compressing the mineral wool felt between the one or two heated clamping plates, notably during at least 5 min, at least 10 min and/or less than 20 min, notably less than 15 min. The clamping plate(s) are preferably heated to a temperature of at least 520°C, at least 550°C, at least 570°C and/or less than 650°C or less than 620°C, for example, of about 600°C.
In another, preferred embodiment, the compressing of the mineral wool felt is performed within a heated oven. In this embodiment, the mineral wool felt is compressed inside the heated oven between compressing roller(s) and/or compressing belt(s). Particularly in this embodiment, the mineral wool felt may be provided as a continuous mineral wool felt laid down on a conveyor. Particularly in this preferred embodiment, upon entry within the oven, the mineral wool felt may be compressed by roller(s) and/or belt(s) and with the compressing only released once exiting the oven. In this embodiment, the speed of the conveyor may be set so that the mineral wool felt is compressed within the oven for a duration as previously indicated. The heated oven preferably has a heating zone having a temperature between 500°C and 600°C, preferably between 520°C and 570°C.
Particularly after the manufacture of the mineral wool insulation, a facing may be applied on one or each of its major surfaces of the mineral wool insulation as described above. The facing may be an aluminium foil, notably an aluminium foil reinforced by a glass scrim. The facing may be applied on one or both major surfaces of the mineral wool insulation while the surface(s) of the mineral wool insulation are still hot, for example between 50-200°C. Alternatively, the facing may be applied whilst the mineral wool insulation is at room temperature. The facing may be applied on the same site or at a different production plant. The facing may be applied by an adhesive, preferably an inorganic adhesive, for example water glass.
To facilitate assembly of the mineral wool insulation in an oven, the mineral wool insulation as described above may be provided in the form of a pre-cut mineral wool insulation configured to be assembled around the oven by folding it along an edge of the oven, around at least two adjacent sides of the oven, preferably three or four or even five sides thereof or as a rectangular shaped mineral wool insulation to insulate one side of the oven, for example a rear side, with no folding around the edges. The mineral wool insulation as described above may comprise cut outs; these may be convenient for the arrangement of cable ducts or tubing, such as power connections, or for the arrangement of electrical fans or other equipment elements. Further cut outs or notches may be provided to facilitate connection of two adjacent mineral wool insulations. Yet further cut outs or notches may be provided in order to adapt the mineral wool insulation to the design requirements of the household appliance it is intended to insulate.
When installed in an oven, notably within the insulation cavity of an oven, the mineral wool insulation as described above may provide an energy efficiency of at least A, preferably of at least A+, measured according to EN60350.
In accordance with another aspect, the present invention provides an oven having an oven cavity thermally insulated with mineral wool insulation, notably wherein the mineral wool insulation is provided within an insulation cavity surrounding the oven cavity, wherein the mineral wool insulation consists of glass wool fibres and is binder-free, notably organic binder-free. In a preferred embodiment, the oven comprises a mineral wool insulation as described above, having one or more of the features described above. The mineral wool insulation of the oven may comprises glass wool fibres, preferably consists essentially of glass wool fibres, more preferably consists of glass wool fibres.
The oven may be insulated by one, two or three distinct mineral wool insulations, notably as described above. The mineral wool insulation as described above may be a unitary oven mineral wool insulation, covering the bottom, the top and three sides of the oven cavity. Alternatively, a first mineral wool insulation, which is called the "backwall", is provided at the back of the oven cavity whilst a second mineral wool insulation, which is called the "wrapper", covers the top, the bottom and the two sides of the oven cavity. Alternatively, three mineral wool insulation are used for covering the five sides of the oven cavity.
In a preferred embodiment, no plastics foil is used to envelop the mineral wool insulation installed within a cavity of the oven. Because of the high temperature generated by the oven, above the melting point of the plastics of the plastics foil, the plastics foil may melt and damage the oven and render the mineral wool insulation encompassed in the plastics foil ineffective.
Particularly where the mineral wool felt is provided as a continuous mineral wool felt, the mineral wool felt may be provided as a roll of binder-free mineral wool fibres. Before rolling the mineral wool felt, a liner is preferably applied on one major surface of the mineral wool felt. The liner, separating layers resulting from the rolling, facilitates the unrolling as it avoids entanglement of fibres between adjacent layers. The liner may be a plastics liner.
The mineral wool fibres of the mineral wool felt, particularly when the mineral wool fibres are glass wool fibres, may be fiberized by internal centrifugation. The mineral wool fibres subsequent to fiberizing lay down on a conveyor by an air stream, thus forming a continuous mineral wool felt, also known as "air laid mineral wool felt". Fiberizing mineral wool fibres which lay down on a conveyor (or a collecting belt) is particularly adapted for providing mineral wool fibres substantially parallel to the main extension of the mineral wool insulation, notably parallel to the direction of the conveyor. The parallelism of the mineral wool fibres provides a mineral wool felt and a mineral wool insulation having a low thermal conductivity. Generally, the conveyor is a perforated, air permeable belt having a collecting side at which the individual mineral wool fibres are laid down to form the mineral wool felt with the other side of the collecting belt being subjected to reduced pressure (for example by an air extraction fan) to facilitate separation and laying down of the mineral wool fibres from the air stream in which they are carried. The use of an air laid mineral wool felt, as opposed to a mineral wool felt formed by pouring a slurry of loose mineral wool fibres in water onto a water permeable conveyor with subsequent drying, facilitates manufacture of the mineral wool felt.
The mineral wool fibres of the mineral wool felt and of the mineral wool insulation are preferably orientated so that they are as parallel as possible to the major surfaces i.e. perpendicular to the heat flow; this contributes to achieving a low thermal conductivity. It is preferable to arrange for a suitable proportion of the mineral fibres of the mineral wool insulation felt to have a length which, on the one hand is sufficiently long to facilitate interconnection between fibres when the mineral wool felt is compressed (preferably at least 50% of the fibres, more preferably at least 80% of the fibres, having a length of at least 30mm, preferably at least 50mm) and, on the other hand which facilitates alignment of the fibres substantially parallel to the major surfaces of the mineral wool felt (preferably at least 50% of the fibres, more preferably at least 80% of the fibres, having a length less than 150mm or less than 100mm). It is believed that the compressing of the heated mineral wool felt when hot as disclosed herein contributes to achieving this desired fibre orientation in the mineral wool insulation and thus contributes to providing low thermal conductivity.
In a preferred embodiment, the mineral wool fibres are unneedled mineral wool fibres, i.e. mineral wool fibres which are not subjected to needling. Needling changes the orientation of at least some of the fibres of a mineral wool felt by passing a plurality of needles repeatedly through its thickness. Needling increases thermal conductivity. Additionally, it is difficult to needle thin fibres, particularly fibres having diameter, for example, below 4µm. The use of unneedled mineral wool facilitates the desired orientation of the mineral wool fibres as parallel as possible to the major surfaces so as to provide low thermal conduction. Thus, the mineral wool insulation formed from the unneedled mineral wool felt is, likewise, unneedled.
The mineral wool insulation of the invention is significantly different to VIP cores, notably in its structure and properties. Whilst having good thermal conductivity due to their wet-laid mineral wool fibres being very well aligned and parallel to the major surfaces, cores of vacuum insulating panels (VIP) have too high a density, notably above 100kg/m³, to be used in household appliances, notably kitchen ovens as they absorb too much energy; in addition, they generally have insufficient mechanical strength for the required handling.
Particularly when the fibres consist of glass wool fibres, the mineral wool insulation may have one or a combination of two, three or four of the following properties:

i) a density of at least 25 kg/m³, at least 30 kg/m³ or at least 40 kg/m³ and/or less than 70 kg/m³, less than 60 kg/m³ or less than 50 kg/m³; and/or
ii) a surface weight of at least 500g/m², at least 750g/m² and/or less than 2000 g/m², less than 1500g/m², less than 1250g/m²; and/or
iii) a thickness of at least at least 5mm, at least 10mm, at least 12.5mm and/or less than 50mm, less than 30mm, less than 20mm or less than 17.5mm; and/or
iv) a thermal conductivity measured at 250°C of at least 50 mW/m.K, at least 60 mW/m.K and/or less than 90 mW/m.K, less than 80 mW/m.K or less than 70 mW/m.K ;
v) a tearing strength, as determined according to standard EN1608, of at least 15N, at least 20N, at least 30N and/or less than 60N, less than 50N or less than 40N; the tearing strength (or tensile strength) is the maximum recorded tensile force parallel to the mineral wool insulation faces during the pulling operation, divided by the cross-sectional testing area of the mineral wool insulation.

The thermal conductivity is preferably measured in accordance with EN12667. Preferably, the mineral wool insulation has the combination of features i), iii) and iv).
The mineral wool felt and/or the mineral wool insulation as described above are preferably binder-free, notably organic binder-free, having less than 0.3 wt% binder and preferably less than 0.1 wt% binder. Where a binder is present, the amount of binder, notably the amount of organic binder, in the felt or in the mineral wool insulation may be less than 8% by weight and preferably less than 2% by weight as determined by loss on ignition (LOI) and more preferably less than 0.5% by weight binder. The mineral wool insulation as described above is also preferably free of organic compounds. This reduces undesired off gassing of the mineral wool upon first heating.
The mineral wool felt, notably the continuous mineral wool felt, may have one of more of the following features prior to being exposed to a temperature of at least 450°C and compressed while hot:

i) a density of at least 10 kg/m³, at least 12kg/m³ or at least 15 kg/m³ and/or less than 20 kg/m³ or less than 17 kg/m³;
ii) a width of at least 1m and/or less than 1.5m;
iii) a length of at least 5m, at least 8m or at least 10m and/or less than 20m or less than 15m;
iv) a thickness of at least 5cm, at least 10cm and/or less than 20cm or less than 15cm. In a preferred embodiment, the mineral wool felt has the features i), ii) and iv).

The mineral wool fibres of the mineral wool insulation described above may be glass wool fibres or rock wool fibres (also known as stone wool fibres). In a preferred embodiment, the mineral wool fibres are glass wool fibres, notably virgin glass wool fibres. Preferably, the mineral wool fibres, notably glass wool fibres, make up at least 70 wt%, preferably at least 80 wt% and more preferably at least 90 wt% of the mineral wool insulation.
Particularly when the mineral wool fibres are glass mineral wool fibres, the glass mineral wool fibres may comprise: > 55 wt-% silicon oxide (SiO₂) and/or < 10 wt-% aluminium oxide (Al₂O₃); and/or an alkali/alkaline-earth ratio of their composition which is > 1; and/or a combined quantity of CaO and MgO < 20 wt-%; and/or a combined quantity of Na₂O and K₂O > 8%wt. In a preferred embodiment, the glass mineral wool fibres are C-glass wool fibres. The glass wool fibres may have a softening point in the range 600-750°C, notably in the range 650-700°C. The glass wool fibres may have a glass transition temperature in the range 500-600°C.
Particularly when the mineral wool fibres are rock mineral wool fibres, the rock mineral fibres may comprise: between 30 and 55 wt-% SiO₂ and/or between 10 and 30 wt-% Al₂O₃; and/or an alkali/alkaline-earth ratio of their composition which is < 1; and/or a combined quantity of CaO and MgO ranging from 20 to 35 wt-%; and/or a combined quantity of Na₂O and K₂O < 8 wt%; and/or a total iron content expressed as Fe₂O₃ of between 4 and 10 wt-%. The rock wool fibres may have a softening point in the range 900-1200°C, notably in the range 1000-1100°C.
The term "softening point" as used herein means the temperature at which the mineral fibre composition deforms under its own weight and which corresponds to a viscosity of 10^7.6 poise (10^6.6 Pa.s). The softening point may be determined by Vicat method in accordance to ISO 306.
The mineral wool fibres of the mineral wool insulation felt and/or the mineral wool insulation as described above may have an average diameter of less than 8µm, preferably less than 6µm, more preferably less than 5 µm. The mineral wool fibres may have an average diameter of at least 2.5µm, at least 3µm or at least 4µm. In one embodiment, the mineral wool insulation has a density of less than 40kg/m³, preferably less than 30kg/m³ and comprises glass wool fibres having preferably an average fibre diameter of less than 4µm. That combination of features provides a better thermal insulation and an improved energy efficiency for an insulated oven, particularly with respect of an oven insulated by an otherwise similar but needled mineral wool insulation.
The mineral wool fibres of the mineral wool insulation as described above may have a length of at least 30mm, at least 50mm and/or less than 150mm or less than 100mm. Whilst not wishing to be bound by theory, having longer fibres than, for example, short fibres, for example those used in cores of vacuum insulation panel, is believed to increase the connection between the fibres when compressing the fibres while hot.
The mineral wool insulation as described above may be free of fluorine compound(s) and/or free of mineral oil and/or free of organic compound(s). Upon being heated to a temperature of ≥ 100°C or ≥ 200°C, notably about 350°C, for example prior to assembly in an appliance, the mineral wool insulation preferably releases no more that the following levels of one or more of the following compounds (expressed in mg of compound per kg of mineral wool insulation):

Formaldehyde (mg/kg): ≤ 3, ≤ 2, ≤ 1.5, ≤ 1, ≤ 0.5, ≤ 0.1; and/or
Ethanal (mg/kg): ≤ 4, ≤ 3 or ≤ 2; and/or
Combination of propanal, butanal and pentanal (mg/kg): ≤ 1, ≤ 0.5 or ≤ 0.02; and/or
Methylisocianate (MIC) (mg/kg): ≤ 0.005; and/or
Acetone (mg/kg): ≤ 20, ≤ 15 or ≤ 10; and/or
Fluorine compounds, particularly hydrogen fluoride and/or carbonyl difluoride (mg/kg) at 350°C : ≤ 0.5 or ≤ 0.3 or ≤ 0.1; and/or
Total volatile organic compounds (VOCs) (mg/kg): ≤ 25, ≤ 15 or ≤ 10.

The said heating to a temperature ≥ 100°C or ≥ 200°C, notably about 350°C, may be the first heating of the mineral wool insulation to such temperatures. Such heating may comprise passing heated air having a temperature ≥ 100°C or ≥ 200°C or ≥ 300°C and/or ≤ 500°C or ≤ 400°C through the mineral wool insulation. Alternatively, or additionally, the mineral wool insulation may satisfy the aforementioned level of emissions when first raised to such temperatures once assembled in an appliance, for example, during first use of an oven or a first pyrolytic cleaning cycle of an oven.
A method in which

providing the binder-free mineral wool felt comprises providing an air-laid mineral wool felt comprising :
forming glass fibres by internal centrifuging of a glass melt;
carrying the glass fibres in an air stream towards a collecting belt;
forming an air-laid mineral wool layer by laying down the glass fibres from the air stream on the collecting belt;
optionally rolling the air-laid mineral wool layer to provide a roll of mineral wool suitable for transportation; and
optionally subsequently unrolling the roll of mineral wool to provide the mineral wool felt for forming the mineral wool insulation;

Rolling the air-laid mineral wool layer to provide a roll of mineral wool suitable for transportation preferably comprises applying a liner, for example a sheet of plastics or paper, to one major surface of the mineral wool layer prior to rolling; the liner which separates the layers within the roll facilitates transport of the roll and the unrolling as it avoids entanglement of fibres between adjacent layers. Where such a liner is used, the liner is preferably separated from the mineral wool layer, for example during unrolling of the roll , prior to the mineral wool layer being used to provide the mineral wool felt.
When unrolled, the layer of mineral wool may have:

i) a width of at least 1m and/or less than 1.5m; and/or
ii) a length of at least 5m, at least 8m or at least 10m and/or less than 20m or less than 15m; and/or
ii) a thickness of at least 5cm, at least 10cm, at least 20cm, at least 30cm and/or less than 60cm or less than 50cm.

An embodiment of the invention will be described in more detail, by way of example only, with reference to the attached drawings of which:

Fig. 1 is a schematic side view of part of a production line;
Fig. 2 is a chart of thermal conductivity with respect to temperature.

A first glass wool felt and a second glass wool felt are firstly formed by fiberizing glass wool fibres 10 by internal centrifugation which are subsequently air laid down on a conveyor 20, thus forming a first continuous felt 10 of glass wool fibres 11 and a second felt of glass wool fibres (not shown), each having a width of about 1.2m, a length of about 10m, a thickness of about 15cm and a density of about 10kg/m³. No binder or organic compound is used or projected towards the fibres during the steps described in this example. Each continuous felt may be rolled up, a plastics liner being provided over a major surface of the felt before being rolled up, and shipped to a different site for further processing.
As illustrated in Fig 1, the first felt 10 fed on a conveyor 20 is compressed between two hot clamping plates 30,31. One plate 30 supporting the felt is fixed whilst the other plate 31 is movable towards the first felt. The plates are pre-heated so that, when compressing the felt 10, the clamping plates 30,31 have a temperature of about 570°C. Due to this temperature, during the compressing and heating step, the temperature within the felt 10 of glass fibres reaches about 550°C. Once the temperature of the clamping plates 30,31 is about 570°C, the clamping plates 30,31 are used to compress the felt of glass wool fibres during about 10 minutes at a pressure of about 20kPa, thereby forming a mineral wool insulation 12 having a thickness of about 30mm, a weight of about 1500 g/m² and a density of about 50kg/m³. Following the heat and compressing step, the mineral wool insulation 12 is cooled down at room temperature.
A second mineral wool insulation (not shown) is manufactured for comparison from the second mineral wool felt. The second mineral wool insulation is manufactured by needling the glass wool fibres of the second mineral wool felt, the needling being facilitated with a needling aid, so that the second mineral wool insulation has a thickness of about 30mm, a weight of about 1500 g/m² and a density of about 50kg/m³.
The the thermal conductivity with respect of temperature of the mineral wool insulation 12 of the specific example and of the comparative example is shown in Fig 2.

Energy efficiency tests, in accordance with EN60350, were also conducted on two different ovens, each having an A+ label but with different volumes (76L and 71L), operating either in "forced air" mode, "conventional" mode or in "ECO" mode. The reference material (comparative example) is a needled glass wool insulating panel having a density of about 60kg/m³ and a thickness of about 20mm. The comparative mineral wool insulation made of glass wool fibres, manufactured according to the invention, has a density of about 60kg/m³ and a thickness of about 20mm. Comparative data are provided below. As seen in the table below, the panel according to the invention provides a better, lower energy efficiency of the oven than the needled insulating panel (difference of energy consumption Δ).

		Reference		Invention
Oven	Function	Material	Energy consumption - Wh	Material	Energy consumption - Wh	Δ
A+ label 76L	Forced air	needled 60/20	870	HP 60/20	850	-20
A+ label 76L	Conventional	needled 60/20	940	HP 60/20	920	-20
A+ label 76L	Eco	needled 60/20	660	HP 60/20	620	-40
A+ label 71L	Forced air	needled 60/20	770	HP 60/20	740	-30
A+ label 71L	Convetional	needled 60/20	930	HP 60/20	900	-30

References in the figures

10: glass wool felt
11: glass wool fibres
12: compressed mineral wool insulation
20: conveyor
30: unmovable clamping plate
31: movable clamping plate

Claims

An oven, notably a domestic oven, having an oven cavity thermally insulated with binder-free mineral wool insulation, notably self-supporting binder-free mineral wool insulation, wherein the mineral wool insulation is provided within an insulation cavity surrounding the oven cavity,
wherein the mineral wool insulation comprises unneedled mineral wool fibres; and

wherein the mineral wool insulation has a density of less than 80 kg/m³.
An oven according claim 1, wherein the mineral fibres of the mineral wool insulation comprises glass wool fibres, preferably consists essentially of glass wool fibres, more preferably consists of glass wool fibres.
An oven according to any preceding claim, wherein the mineral wool insulation has one or more of the following features:
- a density of less than 60 kg/m³; and/or

- a density of at least 25 kg/m³; and/or

- a thickness in the range 10-30mm; and/or

- a weight in the range 60-4000 g/m², notably in the range 500-2000 g/m²; and/or

- a thermal conductivity measured at 250°C in the range 50-90 mW/m.K ; and/or

- glass wool fibres having an average diameter of 2.5-8µm ; and/or

- a tearing force in the range 15-60 N.
An oven according to claim 3, wherein the mineral wool insulation has one or more of the following features:
- a density of less than 50 kg/m³; and/or

- a weight in the range 500-1500 g/m²; and/or

- a thermal conductivity measured at 250°C in the range 50-80 mW/m.K; and/or

- glass wool fibres having an average diameter of 2.5-5µm; and/or

- a tearing force in the range 20-40N.
An oven according to claim 3 or claim 4, wherein the mineral wool insulation has one or more of the following features:
- glass wool fibres having an average diameter of ≤ 4µm; and/or

- a density of less than 40 kg/m³, preferably less than 30kg/m³.
An oven in accordance to any preceding claim, wherein the oven has an European energy efficiency of at least A, preferably of at least A+, according to EN60350.
An oven according to any preceding claim, wherein when first heated to 350°C, the mineral wool insulation releases:
- less than 0.5 mg of fluorine compounds per kg of the mineral wool insulation, preferably less than 0.3 mg of fluorine compounds per kg of the mineral wool insulation; and

- less than 3 mg of formaldehyde per kg of the mineral wool insulation, preferably less than 2 mg of formaldehyde per kg of the mineral wool insulation, more preferably less than 1.5 mg of formaldehyde per kg of the mineral wool insulation.
A method of manufacturing mineral wool insulation, notably self-supporting mineral wool insulation, having a density of less than 80 kg/m³ and suitable for insulating a household appliance, notably an oven in accordance to claims 1-7; comprising:
- providing a binder-free mineral wool felt comprising mineral wool fibres, notably glass wool fibres ;

- exposing the mineral wool felt to a temperature of at least 450°C, preferably at least 500°C ; and

- compressing the mineral wool felt while hot to form the mineral wool insulation.
A method in accordance with claim 8, wherein the mineral wool fibres are glass wool fibres and wherein, compressing the mineral wool felt while hot to form the mineral wool comprises exposing the mineral wool felt to a temperature in the range 520-570°C.
A method in accordance with any of claims 8-9, wherein compressing the mineral wool felt while hot to form the mineral wool insulation comprises compressing the mineral wool felt at a pressure between 15-35kPa.
A method in accordance with any of claims 8-10, wherein compressing the mineral wool felt while hot to form the mineral wool insulation comprises decreasing the thickness of the mineral wool felt by at least 3 times, preferably at least 5 times and/or less than 15 times or less than 10 times with respect of the thickness before compressing the mineral wool felt while hot to form the mineral wool insulation.
A method in accordance with any of claims 8-11, wherein the compressing the mineral wool felt while hot to form the mineral wool insulation comprises maintaining the mineral wool felt under pressure during
- at least 30 seconds, preferably at least 5 minutes; and/or

- less than 15 minutes, preferably less than 10 minutes.
A method in accordance with any of claims 8-12, wherein the compressing the mineral wool felt while hot to form the mineral wool insulation comprises compressing the mineral wool felt by roller(s) and/or belt(s) inside a heated oven having a heating zone at at least 450°C.
A method in accordance with any of claims 8-13, further comprising providing a facing, preferably an aluminium foil and/or a glass scrim, to at least one major surface of the mineral wool insulation.
A method in accordance with any of claims 8-14, wherein the mineral wool felt comprises unneedled mineral wool fibres.