METHOD FOR CONTINUOUS PRODUCTION OF MINERAL WOOL SLABS

Abstract: Method for continuous production of mineral wool slabs from a mineral wool web consisting of mineral wool fibres collected on a perforated conveyor belt in an airborne state, to which fibres a curable binder has been added during or before the collecting, said binder being cured under compression of the mineral wool web to a desired density between two compression bands during the curing. To impart to the finished mineral wool slabs a varying density in the direction of thickness of the slabs in order to attain improved strength properties, at least part of the web is compressed before the curing in a direction perpendicular to the plane of the web in such a way that a permanent compression of the mineral wool will result compared to the remaining part of the mineral wool web.

Description: Method for continuous production of mineral wool slabs. The present invention relates to a method for the production of a mineral wool product from a mineral wool web consisting of mineral fibres having been collected on a perforated conveyor belt in an airborne state, to which fibres a curable binder has been added during or before the collecting, said binder being cured under compression of the mineral wool web to a desired density between two compression bands during the curing. In mineral wool slabs in the shape of mineral fiber mats or fiber plates, in particular for floor and roof in¬ sulation, it is on account of specific loads stemming from persons walking on the insulation layer, necessary to use mineral wool having a rigidity which by far surpasses what is needed for any evenly distributed, load. ' As the more rigid mineral wool contains more fibrous material than a less rigid mineral wool, it is both heavier and more costly to produce than a less rigid one, an increased insulating capacity, however, not resulting. The problem of using a more rigid mineral wool than necessary for ob¬ taining a desired insulating capacity, is also known from outside insulation of walls, where a hard and wear-resistan outer surface is required. It is therefore commonly used to make such insulation of composite materials or several layers of varying rigidit and/or structure. Such insulations may either be manufacture on the building site by laying out several layers differing from one another, or during the production of the mineral wool, varying webs of mineral wool being after the curing of the binder cut off or glued together, possibly by cuttin up one web into slices which are then put together into a pressure-resisting sheet, the desired wearing capacity bein attained with respect both to the diversified load and to the. more .concentrated load. These methods for increasing the wearing capacity in case of a concentrated load, however, en tails considerable extra handling of the mineral wool, which results in comparatively great costs when establishing the insulation as a whole. To reduce the costs in connection with the establishing' of an insulation having a different density in its various layers, it has often been tried to produce mineral woolslabs with for instance light and porous cores and pressure di¬ stributing layers on one side or on both sides. From DAS 1.295 837 a slab consisting of several layers with varying " rigidity is known. In the specification it is stated that a slabof mineral wool fibres is made, to which fibres 15 - 25% of binder is added. The slab is compressed 3 to a specific weight of between 0.008 and 0.06 g/cm and then cured. Another slab of uncured wool is put on topthere¬ of or put under the slab first made, after which both slabs are brought into a heated press or through heated rollers, a pressure being maintained during the curing that gives the cured slab a specific weight of between 0.09 and 0.26 3 g/cm . This method is not satisfactory when a continuouspro¬ duction is desired. Likewise it is not advantageous if the puttingtogether of a cured and an uncured slab gives a sharp delimitation between the various materials having a varying specific weight. Prom the specification to German patent no. 832,201 it is known on part of a mineral wool web to add additional mineral wool before the assembled web is compressed and cured. By this method those parts of the mineral wool web coated with additional mineral wool will get a higher speci¬ fic weight than the remainder of the web. However, the areas with a higher specific weight will extend throughout the thickness of the whole web, while no improvement is obtained in the areas, where no additional mineral wool has been added. A general increase of the wearing capacity with, respect to concentrated loads cannot be attained without covering the whole web with an additional layer of mineral wool. The object of the present invention is to provide a method according to which mineral wool slabs having in¬ creased resistance to concentrated loads can be made. fibrous material not having to be added to any greater ex¬ tent apart from what is necessary for the wearing capacity in case of an evenly distributed load. In other words, the object is to provide a method, according to which mineral wool slabs with a specific weight varying in the direction perpendicular to the length and width dimensions can be continuously manufactured. This object is. attained according to the invention by means of a method of the kind mentioned in 1 e : __nt_.c<_uction, said method being characterized according to the invention by the subject matter of the characterizing clause of claim 1. The invention is based on the observation that the uncured mineral wool, to which a binder has been added, may be compressed in advance for the attainment of a permanent compression being retained also during the final curing, in such a way that the pre-compressed parts of the mineral wool web get a greater specific weight than the remaining parts of the mineral wool web. It is, therefore, possible wi the method according to the invention to produce mineral wool slabs having a comparatively light lower surface and a rigid, comparatively hard upper surface/which is able to resist concentrated loads and to distribute these loads ove a greater part of the underlying mineral wool, which conse- quently does not have to be of an essentially greater strengt than is necessary for carrying the evenly distributed load. The specific weight varying through the height of the minera wool slab makes it possible to produce slabs having the same average specific weight, said slabs being more resistant to the most frequent influences, and also slabs, which with a smaller average specific weight y retain the same fcesistanc as before. The insulating capacity is not influenced by the increase of strength or by the reduced consumption of mate¬ rial, depending on what it aimed at. By mineral wool is normally and in connection with the present invention understood synthetically produced mineral wool. Synthetically produced mineral wool consists of fibres which as to chemical composition differ from the natural fibres, asbestos. However, synthetically produced mineral wool may also vary as to chemical composition and may in general terms be called glass wool, rock wool and slag wool. Besides, the plants where the mineral wool is made, will differ in accordance with the ype of fibres or the type of the finished produc . The method according to the invention may vary in ac¬ cordance with the plant, on which the mineral wool web is produced. These embodiments are defined in claims 2 and 4. Normally, it is necessary for the compression before the curing to take place at such a pressure that the com¬ pressed part of the mineral wool web is reduced in thickness to approx. one tenth of its original thickness. Immediately after the compression, the mineral wool will tend to go back to a.somewhat greater thickness, but after the curing the compressed mineral wool will become more rigid and get a greater specific weight than the not compressed or to a smaller degree compressed mineral wool. The invention will be describe in detail in the following with reference to the drawing, in which fig. 1 shows an example of a plant for the manufacture of for instance glass wool, said plant being intended for the carrying out of the invention, figs. 2 and 3 shows an intermediary product made from for instance stone or slag wool, the fibres being at first deposited in the form of a primary web, then by means of a pendulum boom laid out with overlappings to make up the whole thickness of the uncured mineral wool web, fig. 4 shows an example of a plant, in which a part of the fibres are collected on an inserted collecting- band for the formation of a partial web, and fig. 5 shows a plant for carrying out the method ac¬ cording to the invention, by means of which the mineral wool web is split. In fig. 1 a channel 1 for transporting molten raw ma¬ terials to a series of spinning means 2 is shown. The spinnin means 2 draw the molten raw material out into fine fibres. and to the fibre flow 3 thus produced an atomized binder is added in- conventional way (not shown) . The fibre flow 3 is deposited on. a continuous perforated conveyor belt 8, on which the thickness of the layers of the fibre belt 7 increases in time with a definite part of the conveyor belt passing the spinning or fibremaking means 2. At for instance every second flow of fibres a pair of rollers 4 has been inserted, said rollers compressing the flow of fibres 3 into a pre-compressed fibrous web 5. The finished fibrous web 7 is thereby brought to consist of pre-compress fibre web 5 alternating with light and airy fibre webs 6. In stead of the position of the rollers 4 shown here, which is only shown by way of example, the rollers, which may als be in the shape of pressing bands or plates, may be positio at whichever of the fibremaking means and may thus.vary from every second one of them as to positioning. An embodiment o the arrangement may be that the rollers 4 are placed at for instance the three last fibremaking means in downstream direction. Hereby a comparatively soft, airy part of the lower part of the mineral wool web will be attained, the upper part thereof forming an integral part of the entire pr duct and having a greater specific weight and a more solid texture. When the fibrous web in a conventional way is transported through a curing furnace, the web may be sub- jected to an additional compression from the bands transport ing the mineral wool web through the curing furnace. In figs. 2 and 3 a primary web 21 is seen, said web having been collected from one or more fibremaking means on a perforated conveyor belt. The primary web 21 is compressed or rolled on a part 22 of its width and then, by means of a conventional pendulum .means, which may for instance be of the type known from GB patent no. 1 035 688, foded into a web having a considerable thickness (t_) . The part 22 of the primary web, which is rolled, may vary for example 1/10 to 1/2 of the full width of the primary web, depending on the desired thickness (t 2 ) of the mineral wool web with a greate density. During the subsequent pressing in the curing furnace, the portion (t,,) namely forms that part of the finished product, which has greater density and thus greater rigidity than the underlying fibrous material. In fig. 4 another embodiment of the invention in con- nection with a method for producing mineral wool is shown. In the fibre flow 42, which is delivered by the fibremaking means 52, an intermediary conveyor belt 43 has been inserted, said belt being perforated and in a conventionalway being pro¬ vided with a low pressure chamber at its under surface to attain an effective collecting of fibres. The fibrous web 44 thus collected is rolled or pressed at 45, and the compres¬ sed web 46 is then transported to be joined with the web 49, which has been collected at a normal, perforated collecting band 48. The webs ' 46 and 49 are then being conveyed to subsequent treatment in a curing furnace. The compressionmay as mentioned before be carried out by rolling or compression of partial portions of the uncured mineral wool web. This makes it possible to carry out the rolling with for instance patterned rollers or with rollers having particularly raised portions or linear portions. By using profiled rollers, products having a lattice-like structure, this structure consisting of mineral wool with a greater spe¬ cific weight and rigidity than the remaining part of the pro¬ duct, are obtained. As a further embodiment of the method for production of mineral wool according to the invention, a further method is described with reference to fig. 5, according to which a mineral wool web 51, which has been desposited through a direct laying out of fibres in full thickness or by pen- dulum laying of a primary web, is split into two or more layers 54,55. The mineral wool web 51 is taken through some rollers 52 for the formation of a more uniform structure, thickness and specific weight of the web before the splitting. The splitting may be carried out in a conventional way by means of band saws 53 or the like. One or more of the layers, made by the splitting, is brought to a rolling or pressing between several succeding pair of rollers 56, upon which the the layers are then joined again to form an integral web 57. Before being brought into the curing furnace 59, the integral web may be rolled between additional pair of rollers 58. With respect to sound-insulating mineral wool product which are to be self-supporting, it is for instance possibl to roll or compress the middle part of the uncured mineral wool web, the finished, cured product thereby attaining a hard, rigid core with porous, sound-absorbing side surfaces. The integrated, finished mineral wool product may be composed by parts, the looser ones of which having a densi- 3 ty in the area of from 7-300 kg/m . Depending on the use aimed at this part will, however, preferably be within the 3 area of 20-180 kg/m . The solid, pre-compressed part may attain a density 3 in the area of 20-600 kg/m , preferably 40-350 kg/m . Example A mineral wool slab with an average specific weight o 3 83 kg/m was produced by splitting a mineral wool web into two partial webs, one of which, being compressed for the attainment of a permanent compression, making out 30% of the hight of the total mineral wool web. During the compressing the partial web was compressed to approx. 1/10 of its original thickness and then the pressure was relieved The two partial webs were then joined and compressed to attain the desired finished thickness and simultaneously cured by hot air being blown through it. The mineral wool slab attained had a specific weight varying through the thickness of the slab, the specific weight being at one surface 138 kg/m 3, while it was 73 kg/m3 at the other surfac The point-pressure strength was approx. 60% bigger with a hard surface than with a slab having essentially a uniform 3 specific weight throughout its whole thickness of 83 kg/m . A homogenous slab with a correspondingly increased point- pressure strength would have its specific weight increased 3 by more than 10 kg/m .

Claims: WE CLA-IH: 1. Metfrσd for continuous production of mineral wool slabs from a mineral wool web consisting of mineral wool fibres collected on a perforated conveyor belt in an airborne state, to which fibres a curable binder has been added during or before the collecting, said binder being cured under compression of the mineral wool web to a de¬ sired density between two compression bands during the curing, c h a r a c t e r i z e d in that at least part of the web is compressed before the curing in a direction perpendicular to the plane of the web in such a way that a permanent compression of the mineral wool will be brought about compared to the remaining part of the mineral wool web. 2. Method according to claim 1, in which method the.mineral wool web before the curing is split parallelly to the plane of the web in at least two partial webs, c h a r a c t e r¬ i z e d in that at least one of the partial webs passes between at least one pair of rollers or a pair of converging conveyor belts. 3. Method according to claim 1, in which method- he.mineral wool web is made by folding the thinner primary web of mineral wool, the primary web being preferably placed in such a way that an angle to the mineral wool web is formed, c h a r a c t e r i z e d in that the permanent compression is established in a part of the width of the primary web, the folding being carried out in such a way that the com¬ pressed mineral wool will be placed in the desired area of the mineral wool web. 4. Method according to claim 1, in which method the air¬ borne mineral fibres are collected on two or more perforated bands for forming two or more partial webs, which are then brought together for forming the mineral wool web, c h a- r a c t e r i z e d in that at least one of the partial webs is compressed between pairs of rollers or converging pairs of conveyor belts. 5. Method according to claims 1, 2, 3, or 4, c h a- r a c t e r i z e d in that the mineral wool during the compression is reduced to a tenth of its original thickness

Inventors: CRIDLAND IAN, LARSOE POUL VERNER, CRIDLAND, IAN, LARSOE, POUL, VERNER
Applicants: ROCKWOOL INT, ROCKWOOL INTERNATIONAL A/S
Application year: 1987
Main classification: E04B1
IPC codes: D04H1, E04C2