TEMPERATURE RESISTANT MINERAL WOOL PRODUCT

Abstract: Temperature resistant mineral wool product in particular comprised of glass fibers, which is characterised in that fine inorganic particles are added onto the fibers of at least an outer layer of the products while the fibers are in the non-plastic state, with said fine inorganic particles favoring a crystallisation tendency of the fibers when said product is exposed to heat.

Description: Description Temperature Resistant Mineral Wool Product The present invention relates to a temperature resistant mineral wool product particularly comprised of glass fibers. Mineral wool products are i.a. used for thermal insulation. In particular they are also used in the form of fire protection elements . It is an object of the invention to increase the temperature resistance of mineral wool products already having their final dimensions at least in sections thereof such that they meet higher standards of fire protection while still providing ease of manufacture. The invention is based on the insight that an increased temperature resistance of a mineral wool product can be obtained by applying substances favoring crystallisation of the individual vitreous fibers onto the fibers while the latter are in a cold state. The subject matter of the invention thus is a mineral wool product in particular comprised of glass fibers, which is characterised in that fine inorganic particles are added onto the fibers of at least an outer layer of the products while the fibers are in the non-plastic state, with these fine inorganic particles favoring a crystallisation tendency of the fibers when the product is exposed to heat. Preferably the particles are applied on the fibers of the product already having its final dimensions in an aftertreatment by means of a foam impregnation process, with inorganic oxides, hydroxides and/or silicates particularly being used as these particles. Foam impregnation is, for example, described in DE 44 35 918 the disclosure of which is herewith incorporated by way of reference. By foam impregnation of the mineral wool product surface it is possible to purposely add a defined amount of the particles on fibers which are directly exposed to the elevated temperature loads. Particularly in the case of these fibers, crystallisation is required in order to increase their temperature resistance. Use of particles comprising aluminum oxide, aluminum silicates, kaolinite, china clay and/or aluminum hydroxide was found to be particularly advantageous. The average grain size of particles is preferably less than 10 μm, in particular less than 1 μjTt, with application of these particles on the outer layer(s) of a mineral wool product being possible by any known methods such as e.g. impregnation, spraying and coating. The particles are preferably provided in an amount between 1 and 20 kg/m 3 . It is particularly advantageous if the particles are present on the surface of the mineral wool product in an amount between 30 and 200 g/m 2 , preferably in an amount between 70 and 100 g/m 2 . With respect to adhering the particles to the fiber surfaces it was found suitable to use the binding agent used for immobilising the fibers while in the hot state, or to use an additional binding agent . The additional binding agent preferably comprises inorganic substances such as silica sol and waterglass. Mineral fibers having a composition wherein the difference between the sum of amounts in weight per cent of oxides of sodium, potassium, calcium, magnesium, barium and possibly boron and twice the amount in weight per cent of aluminum oxide is at least 25, preferably at least 40, can preferably be used for the measures according to the invention in order to increase the temperature resistance thereof. Thus it is also possible to use mineral fibers having the following constituents in weight per cent for producing mineral wool products according to the present invention: Si0 2 40 to 60 A1 2 0 3 0. 5 to 6 CaO 20 to 45 MgO 5 to 15 Na 2 0 3 to 12 K 2 0 0 to 10 Na 2 0 + K >° 3 to 15 P 2 O 5 0 to 5 Ti0 2 , Fe |0 3 , BaO, MnO 0 to 5 or Si0 2 48 to 67 A1 2 0 3 0 to 8 Fe 2 0 3 0 to 12 CaO 16 to 35 MgO 1 to 16 Na 2 0 + K 2 0 0 to 6.5 P 2 0 5 0 to 5. In a preferred embodiment of the present invention, the mineral wool product has the form of boards for fire doors . In elevated temperatures such as those occurring in a fire, mineral fibers generally lose their mechanical properties, soften, and sinter together if temperatures continue to rise. If, on the other hand, their vitreous state is modified by crystal formation, then the fibers are capable of resisting much higher temperatures without suffering an important reduction of their mechanical strength. Crystallisation of the fibers implies the formation of nuclei from which crystallisation starts out to propagate within the fibers. The crystallisation rate depends in a considerable degree on the number of nuclei, temperature, and time. In mineral wool products which are to be subjected to elevated temperatures it is therefore desirable if as many crystallisation nuclei as possible are formed inside the fibers in a minimum period of time at an elevated temperature. In accordance with the present invention, fine inorganic particles are thus added onto the fiber surfaces, preferably by foam impregnation. In the presence of elevated temperatures, softening of the fibers is prevented by the fact that on the one hand, the added particles themselves have higher melting points than the glass fibers, and on the other hand heat transfer is delayed, which favors the crystallisation tendency of the fibers. Another advantage resides in the fact that it is sufficient if the application of particles on fibers in a mineral wool product according to the present invention is performed to a depth of approx. 1 mm from the product surface. Starting out from the fibers to which particles were added, crystallisation continues in a direction towards the interior of the mineral wool product such far that temperature resistance can be attained at least in a section of the mineral wool product. The invention will in the following be described in detail by reference to two examples. Example 1 The mineral fiber used had the following composition in weight per cent: Si0 2 51 A1 2 0 3 3 Fe 2 0 3 0.3 CaO 31 MgO 10 Na 2 0 5 K 2 0 0.5. This mineral fiber, while in the cold state, was provided on its surface with a material comprising the following components: 1.3 % stabiliser 37.63 % china clay 59 % silica sol 2.0 % foaming agent. This impregnation was applied as a foam in an amount of 150 g/m 2 with an average grain size of the china clay of 0.1 μm. The sample thus prepared was subjected to a fire resistance test inside a small flame furnace, wherein the temperature increase was measured on the side facing away from the flame. After 90 minutes, the temperature on the side facing away from the flame was 70°C, and after 120 minutes a thickness reduction of the sample of only 7 mm was ascertained. In comparison, a corresponding mineral wool lacking impregnation will show complete sintering together of the side receiving the flame load, i.e. a thickness reduction of approx. 30 mm for a product originally having a thickness of approx. 63 mm. Example 2 The mineral fiber used had the following composition in weight per cent: SiO- 60 A1 2 0 3 1 Fe 2 0 3 6 CaO 20 MgO 9 Na 2 0 4 2 0 0 . 5 . This mineral fiber was provided at its surface with the same material and with the same amount as in Example 1. After 90 minutes, the small flame test carried out on it resulted in a temperature of 82°C on the side facing away from the flame, and after 120 minutes the sample was found to have lost only 3 mm of its thickness . Thanks to the improved thermal properties which can be imparted to a conventional mineral fiber by the present invention, the like mineral wool products may particularly be used as fire protection elements in fire doors. As the mineral fibers used are physiologically decomposable, further fields of application are advantageously open to them.

Claims: Claims 1. Temperature resistant mineral wool product in particular comprised of glass fibers, characterised in that fine inorganic particles are added onto the fibers of at least an outer layer of said product while the fibers are in the non-plastic state, with said fine inorganic particles favoring a crystallisation tendency of the fibers when said product is exposed to heat. 2. Mineral wool product according to claim 1, characterised in that said particles are applied on the fibers of said product already having its final dimensions in an aftertreatment by means of a foam impregnation process. 3. Mineral wool product according to claim 1, characterised in that said particles comprise inorganic oxides and/or silicates . 4. Mineral wool product according to claim 3, characterised in that said particles comprise aluminum oxide, aluminum silicates, kaolinite, china clay and/or aluminum hydroxide. 5. Mineral wool product according to claim 4, characterised in that said particles have an average grain size of less than 10 m, in particular less than 1 μm. Mineral wool product according to claim 5, characterised in that said particles are provided in an amount between 1 and 20 kg/m 3 . Mineral wool product according to one of claims 1 to 6, characterised in that said particles are present on the outer layer of said mineral wool product in an amount between 30 and 200 g/m 2 , preferably between 70 and 100 g/m 2 . 8. Mineral wool product according to one of claims 1 to 7 , characterised in that the binding agent used to immobilise the fibers while in the hot state, or an additional binding agent serves to adhere the particles to the fiber surfaces. 9. Mineral wool product according to claim 8, characterised in that said additional binding agent comprises inorganic substances such as silica sol and waterglass. 10. Mineral wool product according to one of claims 1 to 9, characterised in that the glass of said fibers has a composition wherein the difference between the sum of amounts in weight per cent of oxides of sodium, potassium, calcium, magnesium, barium and possibly boron and twice the amount in weight per cent of aluminum oxide is at least 25, preferably at least 40. 11. Mineral wool product according to one of claims 1 to 10, characterised in that the glass of said fibers has the following constituents in weight per cent: SiO-, 40 to 60 A1 2 0 3 0.5 to 6 CaO 20 to 45 MgO 5 to 15 Na 2 0 3 to 12 K 2 0 0 to 10 Na 2 0 + K : >° 3 to 15 P 2 0 5 0 to 5 Ti0 2 , Fe- !θ 3 - r BaO, MnO 0 to 5 12. Mineral wool product according to one of claims 1 to 10, characterised in that the glass of said fibers has the following constituents in weight per cent: Si0 2 48 to 67 Al 2 0 3 0 to 8 Fe 2 0 3 0 to 12 CaO 16 to 35 MgO 1 to 16 Na 2 0 + K 2 0 0 to 6,5 P 2 0 5 0 to 5. 13. Use of a mineral wool product according to one of claims 1 to 12 in the form of boards for fire protection elements, in particular fire-proof doors.

Inventors: KUMMERMEHR HANS, KUMMERMEHR, HANS
Applicants: SAINT GOBAIN ISOVER, ISOVER, SAINT-GOBAIN
Application year: 1996
Main classification: C04B28
IPC codes: C03C13, C03C25, E04B1