INSULATING ELEMENT AND INSULATION LAYER COMPOSED OF SUCH ELEMENTS

Abstract: An insulating element comprising an insulating layer (1) of mineral fibres and an air permeable protective cover (2) consisting of a non-woven fabric of pre-stressed organic fibres and wholly or partially surrounding the insulating layer.

Description: Insulating element and insulation layer composed of such elements. This invention relates to an insulating element comprising an insulating layer made of mineral fibres and an air permeable protective cover of an organic material, said cover at least partially surrounding the insulating layer. More specifically, the invention relates to heat insulating mineral fibre batts or rolls provided with such protective covers. Insulating batts made from mineral fibres, such as rock wool fibres, are so flexible that they can be adapted to the surfaces or spaces which are to be insulated. However, during the handling of such batts loose fibres or fibre dust tend to be released. This is particularly troublesome when such batts are used for ceiling insulation purposes. Another serious drawback of such batts is that they may cause skin problems. Thus, when such unprotected mineral fibre batts are brought in direct contact with the skin, the fibres extending from the surfaces of such batts tend to penetrate into the skin and to cause itching or local skin irritation. It is well known to provide mineral fibre batts or rolls with protective covers made from a non-woven fabric or polyester fibres. The provision of such a cover on a mineral fibre batt or roll eliminates or at least reduces some of the above mentioned problems but simultaneously creates a new problem, viz. an increased inflammability as the organic fibres are combustible and may even support a fire. The main object of the present invention is to reduce or eliminate the drawback of the prior art protected . mineral fibre insulating elements. The insulating element of the invention is characterized in that the protective cover is made from a material which, when heated to a temperature sufficiently high to set it on fire, contracts with a speed exceeding the speed at which the fire spreads. Surprisingly, it has been found that if embers or a burning match are dropped on an insulating element of the invention, a hole will be formed in the cover but the fire will not spread. In a preferred embodiment of the insulating element of the invention the protective cover consists of a non-woven fabric of pre-stressed organic fibres. The expression "prestressed fibres" as used herein means fibres having inherent stresses, e.g. fibres which during their manufacture have been strecthed to such an extent as to generate tensile stresses in the fibres. When the fibres are heated to melting temperature, the tensile stresses will be released and produce the above mentioned contraction. The protective cover may also consist of a perforated film having inherent tensile stresses. Insulating batts are known which consist of a layer of mineral fibres enclosed in a sealed polyethylene film bag which has been made self-extinguishing by the addition of a fire-retardant agent. Unlike the insulating elements of the invention such insulating batts cannot be compressed and consequently the transport of such batts involves relatively high costs. Furthermore, the addition of a fire-retardant agent to polyethylene results in a considerable increase in the costs of the material and may cause the generation of toxic compounds by thermal decomposition of the polyethylene. The protective cover preferably consists of a non-woven fabric of thermoplastic fibres. A non-woven fabric of pre-stressed polypropylene fibres is particularly suitable. However, the non-woven fabric may also consist of pre-stressed fibres of polyethylene, polyester, polyamide or polyacrylic amide. The use a non-woven fabric comprising a major portion of pre-stressed fibres and a minor portion of soft non-prestressed fibres, such as 10% viscose fibres, provides an insulating element which in addition to being self-extinguishing is particularly soft to touch. Protective covers having a weight of 5-100 g/m 2 and particularly 5-15 g/m 2 are preferred. The insulating layer is preferably completely surrounded by the protective cover, but sometimes it may suffice to apply the protective cover on the main surfaces only or on two opposite sides or ends of the insulating element. The insulating layer preferably consists of synthetic mineral fibres, including rock wool fibres, glas fibres, slag fibres and ceramic fibres. It is preferred to use a mineral fibre layer consisting of rock wool fibres and in particular rock wool fibres prepared by a method comprising the steps of introducing a melt of fibre forming raw material onto the cylinder surface of a rapidly rotating spinning wheel and subjecting the melt thrown out from this surface to the influence of one or more air streams passing over said surface, and optionally adding a binder to the fibres thus formed before collecting them so as to form a fibre layer which optionally is subjected to a doubling, compression and heating in order to cure the binder. The thickness of the mineral fibre layer is preferably between 1 and 30 cm and its density is preferably from 15 to 400 kg/m 3 . The invention also relates to an insulation layer consisting of insulating elements as described above. The invention will now be described in further detail with reference to the drawing which shows a perspective view of an insulating batt according to the invention and with the protective cover partially removed. In the drawing 1 designates a mineral wool layer and 2 a protective cover consisting of a non-woven fabric of organic, pre-stressed thermoplastic fibres.

Claims: P a t e n t C l a i m s 1. An insulating element comprising an insulating layer made of mineral fibres and an air permeable protective cover of an organic material, said cover at least partially surrounding the insulating layer, c h a r a c t e r i z e d in that the protective cover is made from a material which, when heated to a temperature sufficiently high to set it on fire, contracts with a speed exceeding the speed at which the fire spreads. 2. An insulating element according to claim 1, c h a r a c t e r ¬ i z e d in that the protective cover consists of a non-woven fabric mainly consisting of pre-stressed organic fibres. 3. An insulating element according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the non-woven fabric comprises pre-stressed thermoplastic fibres. 4. An insulating element according to any of claims 1, 2 or 3, c h a r a c t e r i z e d in that the non-woven fabric consists of a minor portion of soft non-prestressed fibres. 5. An insulating element according to any of the claims 1-4, c h a r a c t e r i z e d in that the protective cover consists of pre-stressed polypropylene fibres. 6. An insulating element according to any of the claims 1-5, c h a r a c t e r i z e d in that the protective cover has a weight of 5-100 g/m 2 , particularly 5-15 g/m 2 . 7. An insulating element according to any of the preceding claims, c h a r a c t e r i z e d in that the mineral fibres are rock wool fibres. 8. An insulation layer, c h a r a c t e r i z e d in that it is composed of insulating elements according to any of the preceding claims.

Inventors: PETERSEN JOERGEN SKJOLD, PETERSEN, JOERGEN, SKJOLD
Applicants: ROCKWOOL INT, ROCKWOOL INTERNATIONAL A/S
Application year: 1992
Main classification: E04B1
IPC codes: B32B5, E04B1, E04C2