Method and apparatus for supplying a binder to mineral wool

Method and apparatus for supplying binder to newly formed mineral wool fibres by means of several distribution means like nozzles or spreaders (30-33, 36-36, 41-43) while said mineral wool fibres are suspended in an air or gas stream on their way to a collection means (29), which in one or more steps form a final mineral wool path (F-J), whereby the binder or binder mixtures from the different distribution means (30-33, 35-36, 41-43) are supplied to different parts of the fibre suspension and in such amounts--in relation to the fibre flow in that part of the fibre suspension, which is actuated by the respective distribution means--that different layers (e.g. F+J, G+I, H) of the final mineral wool path get different content of binder.

BACKGROUND OF THE INVENT-ON 
Generally mineral wool products are manufactured in that a mineral material 
is melted in a melting apparatus from which the melted material is 
continuously supplied to a fribrillation apparatus. In said fibrillation 
apparatus the melted material is transformed, more or less completely, to 
mineralic fibres which, by means of an air or gas stream, are brought from 
the fibrillation apparatus to a receiver in the form of a perforated 
conveyor on which the fibres lay down in the form of a continuous mat of 
mineral fibres, whereas the air or gas stream moves through the conveyor 
and to an exhaust fan and is from there transported e.g. to a purification 
apparatus. 
The raw materials for the mineral wool consist of stone or slag, and cupola 
furnaces usually are used as melting apparatus for such materials. In this 
case the fibrillation is often made by means of rapidly rotating steel 
cylinders, called spinning wheels, which are water-cooled from inside the 
cylinders, and which are arranged to successively receive the melted 
material. The melted material is thereby moved to one of said spinning 
wheels from which it is thrown to the next spinning wheel, etc. This type 
of arrangement is called the cascade spinning method or the JM-process (JM 
for Johns-Manville). There are generally 2-4 spinning wheels in the 
cascade spinning apparatus. Only rarely more than 4 spinning wheels are 
provided in cascade relationship. 
Parallelly arranged fibrillation apparatus can be used in order to obtain a 
higher capacity. Generally, two identical or mirror symmetrical 
fibrillation apparatus are thereby used, which apparatus are placed side 
by side and between which the melted material is distributed. 
In the manufacture of glass wool there is used more or less convention 
glass raw materials which are usually melted in a tank. In the most usual 
fibrillation method for glass wool the melted material is allowed to flow 
into hollow centrifuges which are mounted for rotation about vertical 
shafts. There are holes in the jacket of the centrifuges and the melted 
glass is by the centrifugal force pressed out through said holes thereby 
forming thin mineral strings, called primary fibres. The actual 
fibrillation is thereafter accomplished by means of strong axially 
directed gas or air jets which flow past the jackets of the centrifuges. 
Also in the fibrillation of stone or slag mineral wool air flows are 
supplied round the spinning wheels. There are several reasons for 
supplying such air flows, for instance for bringing the fibres away from 
the actual fibrillation apparatus and to the collection means, whereby, as 
mentioned above, the fibres deposit on the collection means, whereas the 
gas or air streams pass through the collection means. 
In commercial processes for the manufacture of mineral wool products the 
fibres, just formed, are more or less well suspended in such an air or gas 
stream, which brings the fibres from the fibrillation apparatus to the 
receiver means. If a binder is to be added to the mineral wool fibres, and 
binder is almost always added, the binder is mostly supplied in a finely 
dispersed form to said fibre suspension. Other substances may be supplied 
instead of a binder, or in combination with a binder, for instance a 
wetting agent or a dust binding substance. Often the binder is supplied 
very close the fibrillation apparatus. The reason for supplying the binder 
to the fibre suspension, and not to the mat already formed on the 
receiving conveyor is that is is difficult to have the binder penetrate 
into a mineral wool mat since such mats are tight and the fibres have a 
fine structure as compared with the size of the binder drops. 
There are basically two different principles for the function of the 
receiver means. According to one principle, the originally used principle, 
a final mat is built up on the conveyor of the receiver means, and said 
final mat is then moved on where it is hardened, cooled, divided and cross 
cut etc. Technically this means that the surface weight, for instance 
defined in g/m.sup.2, of the the mineral wool when originally laid down on 
the perforated conveyor is the same as the intended surface weight of the 
final product already. In many cases the second principle gives a better 
result, and according to this principle a relatively thin mat, a so called 
primary mat, is first collected, and said primary path is then, by a 
folding process, in one or more steps, operated so as to build up a final 
mineral wool mat, the surface weight of which corresponds to intended 
surface weight of the final product. The surface weight of the primary 
mineral wool mat may, in many cases, be much less than that of the final 
mineral wool mat, for instance 1/10 thereof or less. 
The stream of air or gas which brings the mineral fibres from the 
fibrillation apparatus to the receiver means is more or less turbulent. 
Tests have shown that the fibres are not completely mixed in the air or 
gas flow, in particular because the distance between the fibrillation 
means the the receiver means is not vary long. This means that fibres 
which are introduced in the said air or gas stream in a certain position 
tend to deposit at a special point or within a special area of the 
receiver conveyor, whereas fibres which are introduced in the air or gas 
flow in another position mainly deposit within another area of the 
receiver conveyor. This observation has been utilized as a basis for the 
present invention. 
The binder of a mineral wool product is often used firstly to prepare the 
mineral wool product for its final field of use. For instance, after a 
mineral wool plate has been inserted between studs and behind final layers 
of a wall the binder has practically no function at all. In other cases 
the binder primarily is often supplied for transport technical and 
mounting technical reasons and only secondarily to fulfil demands of the 
product in its mounted condition. Anyhow a completely constant and 
homogenously distributed binder does not always give an optimum product. 
In cases when there is no need for the same content of binder all over the 
mineral wool product the inner portion of the product has the least need 
for binder. 
It has been suggested that a binder which is homogeniously distributed in a 
mineral wool product manufactured according to normal methods should be be 
completed by an extra supply of binder which is subsequently added on the 
surfaces of the ready product. Said additional binder has to be dried or 
hardened before the product is ready, and therefore this is a two stage 
method. An advantage in such a method is that the main binder can be 
supplied in smaller amounts than is otherwise necessary. The gain thereof 
is, however, consumed by the costs for executing the said two stage 
method. 
SUMMARY OF THE INVENTION 
The present invention offers the possibility of manufacturing mineral wool 
products continuously and in one stage, which products have different 
contents of binder in different parts of the product. 
The invention is based on the observation that there is a certain 
correspondence between a point at the formation of a fibre suspension, on 
its to the receiver means, and a large or small surface area of the 
receiver means. Oppositely a certain part of the receiver means can be 
related to a certain part of the fibre suspension as present at the 
beginning of its transport. Likewise a certain part of the receiver 
surface can be related to a certain part of the final product. According 
to the invention this observation is utilized in that different parts of 
the fibre suspension is given different kinds of binder or mixtures of 
binders, and eventually different dosages, so that different layers of the 
ready mineral wool path or product contain different types of binder or 
mixtures of binders and eventually also different amounts of binder. 
It is thereby particularly interesting to provide a supply of an increased 
amount of binder on the top and/or the bottom surface layer of the 
product. 
According to the invention it is also possible to change the surface layers 
or the inner part of the product by supplying thereon or therein a binder 
of another type, or in another amount. 
In the case where the final mineral wool mat is formed by a one-stage 
method on the receiver means and is built up by a fibre suspension which 
initially moves horizontally and is deposited on a horizontal or obliquely 
upwards extending conveyor, referred to as a long chamber process, the 
upper part of the fibre suspension adjacent the fibrillation apparatus 
generally forms the upper part of the final mineral wool mat, that is the 
upper surface layer of the product. Correspondingly the lower part of the 
fibre suspension generally deposits on the receiver means as the bottom 
layer of the final mineral wool mat, that is the other surface layer of 
product. 
In the case where the final mineral wool mat is built up by mineral wool 
fibres from several fibrillation apparatus following each other, the 
deposit on the receiver means of the fibres from the first one of the 
fibrillation apparatus mainly form the the bottom layer of the final 
mineral wool mat, and the fibres from the last fibrillation apparatus form 
the upper surface layer. 
In the case that the final mineral wool mat is formed of several thin 
primary mineral wool mats that, are laid together, there is a connection 
between the edges of the primary mat in the upper layer and the bottom 
layer of the final product. It is thereby possible to supply a special 
amount of binder to the fibre suspension which deposits adjacent one edge 
of the primary mat, instead of--not in addition to--the main binder. The 
addition of binder thereby is presented in the upper layer or in the 
bottom layer of the final mineral wool mat depending on which edge of the 
primary mat is treated. 
It has been shown that an improved effect is obtained by compressing the 
primary mat edge thus treated. This can be made by means of a roller which 
is compressing the primary path over an area from edge thereof and some 
distance towards the center of the mat, for instance 10-15 cm. 
Correspondingly it is possible to identify the part of the fibre suspension 
which mainly builds up a specific part of the product and to add more 
binder to this part of the mat. It is also possible to add another binder 
or another additive like a colouring substance to a particular mineral 
wool layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 diagrammatically shows the lower part of a melting apparatus 1, from 
which melted mineral flows out through a flute 2 and down on a spinning 
wheel 3 in the form of a stream 4. The melting apparatus can be of 
different types and it is therefore only intimated in the drawing. The 
spinning wheel 3 is driven by a shaft 5 enclosed in a casing 6. An air 
stream 7 flows round the spinning wheel 3 parallelly with the shaft 5 of 
the spinning wheel. The air stream actually flows round the entire 
spinning wheel, but for the sake of clearness it is marked in the figure 
only at the lower side of the spinning wheel. When the melted mineral of 
the stream 4 meets the spinning wheel 3 it wets the spinning wheel but, 
depending on the centrifugal force, the melted mineral is thrown out 
therefrom in the form of fibres 8. The fibres are thrown out radially of 
the spinning wheel 3 but they are deflected by the action of the air 
stream 7. 
The air stream brings the collection means that include a first fibres to 
the collection conveyor 9, which can for instance be a perforated steel 
band extending over rollers 11 and 12 in the direction of travel 10. 
Behind the steel band there is a suction box 13 in which there is a sub 
pressure provided by a not illustrated fan system. The fibres deposit 
on-the conveyor in the form of a mat 14 which is moved away along a path 
of travel by the conveyor 9 as indicated with the arrow 15. 
FIG. 2 shows the method of forming a thicker mineral wool mat by folding a 
thin mat in several successive bows or turns. Numeral 16 in the figure 
shows a thin primary mat for instance like the mat 14 of FIG. 1 having 
side edge areas. The thin mat 16 is carried on a conveyor 17 to a pendulum 
folding means, which comprises two conveyors 18 and 19 between which the 
mat 16 is moved downwards. The conveyors 18 and 19 are, rotatably 
journalled at their upper ends, whereas the lower ends rhythmically 
reciprocate over a second receiving transport conveyor 20 which extends 
perpendicularly to the plane of the drawing and moves with substantially 
less speed than the conveyors 17, 18 and 19. Thereby the mineral wool mat 
deposits in bows 21. 
FIG. 3 is a side view in simplified form of the the same aparatus. The 
primary mat 16 moves down between the conveyors 18 and 19 (see FIG. 2) as 
indicated with the arrow 22 whereby the mat is deposited on the transport 
conveyor 20 in bows 21 which partly overlap and cover each other as 
indicated in FIG. 3. The surface of one edge area of the primary mat 16 
thereby forms one surface layer of the new final mineral wool path, and 
the surface portion of the other edge of the primary path 16 forms the 
opposite surface layer of the new final mineral wool mat. 
Thanks to the properties of the Primary mineral wool mat 16 the new final 
mat now formed on the conveyor 20 by the bows 21 is substantially 
continuous but is thicker than the primary mat 16. The new mat is then 
moved on to means for compressing the mat and for hardening of the binder, 
etc. 
FIG. 4 diagrammatically shows an apparatus for forming and collecting of a 
mineral wool mat having two parallel fibrillation stations. Melted mineral 
flows from a melting apparatus 24 through a twin split flute 25 for melted 
mineral and is thereby distributed to two primary spinning wheels 26 and 
26'. A portion of the melted mineral is transformed to fibres by the 
spinning wheels 26 and 26', and another portion of the melted mineral is 
secondarily transferred to the secondary spinning wheels 27 and 27' at the 
outside of each station and is defibrillated therefrom. The spinning 
wheels are rotated rapidly by means of drive shafts (not shown in the 
drawing). The melted mineral is thrown out from the spinning wheels in the 
form of fibres, and said fibres are, by the action of the air streams 28 
and 28' surrounding all spinning wheels, moved towards the collection 
conveyor as shown by with the arrows A, B, C, D and E. A main amount of 
binder is supplied from binder distribution means which includes a first 
distribution means in the form of centre spreaders 30, 31, 32 and 33 and 
said binder hits the fibre streams A-E. Fibres are thrown out from 
different points of the periphery of the spinning wheels. Only those 
fibres which move in the vertical plane (parallelly with the spinning 
wheel shafts) are shown in the drawing. The binder distribution means also 
includes a second distribution means 35, 41 supplying additional binder to 
the mat as will now be described. A stream of additional binder 34 from a 
second binder supply means which includes nozzle 35 a nozzle 35, which is 
supplied with binder from a conduit 36, is directed to the fibre stream A. 
Similarly a stream of additional binder 37 flowing through a second binder 
supply means which includes channel 38 connected to an opening 39 of the 
wall 40 is is directed to the fibre flow E. A stream of binder 37 is 
formed by a nozzle 41 which is supplied with binder from a conduit 42 and 
with compressed air from a conduit 43. 
The fibre streams A-E move towards the collection conveyor 29 by the action 
of the sub-pressure which is supplied by a suction box (not illustrated) 
provided at the rear side or bottom side of the conveyor 29. The fibre 
stream A thereby is deposited mainly at the area F of the conveyor 29, the 
fibre stream B at area G, etc. It should, however, be noted that there is 
no strict limits between the fibre streams. Normaly the fibres are 
transported in a certain turbulent movement, and therefore the fibre 
streams are mixed with each other so that there are no sharp limits 
therebetween. So, between the areas F and G a mixture of fibres from the 
fibre streams A and B deposits, etc. 
All binder emitting means, that is the centre spreaders 30, 31, 32 and 33, 
the nozzle 35 and the nozzle 41 can be supplied with binder separately 
from each other, and therefore said means can supply different amounts of 
binder by an individual dosing thereof. 
An increased amount of binder can be supplied to a special part of the 
fibre suspension by means of separate nozzles, like the nozzle 35. A still 
more concentrated supply of binder can be provided by supplying the 
additional binder to the fibre suspension closer to the conveyor 29 by 
means of a nozzle like the nozzle 41. 
Since the centre spreaders 30, 31, 32 and 33 distribute their binder evenly 
round the entire periphery thereof said spreaders preferably supply the 
base or main amount of binder, which is the least amount to be present in 
the mineral wool product, and additional binder is supplied, from extra 
nozzles like the nozzle 35 and the nozzle 41, to those parts of the 
mineral wool which are to include more binder than said base amount, in 
particular to the parts forming the surface layers of the mineral wool 
product. 
FIG. 5 shows an example resulting from a process, in which centre spreaders 
have supplied an amount of binder corresponding to the staple H to the 
entire fibre suspension, and in which additional binder has been supplied 
through side nozzles corresponding to the nozzle 35 so that the edges of 
the primary mat, corresponding to the staples F and J, have received more 
binder. The remaining part of the mat, that is, intermediate areas 
corresponding to the staples G and I, has received a medium high amount of 
binder. 
By placing the nozzles for the additional binder at particular places it is 
possible to obtain a more or less restricted effect. It is not, however, 
always desired to provide sharp limits between the areas having different 
contents of binder in a product, and a profile of binder content as shown 
in FIG. 5 often corresponds to an optimum condition. It is possible to 
supply, by the nozzle 35 or the nozzle 41, not only additional binder but 
also binder of another type, solely or in a mixture with the main binder. 
It is easy to see that the above described method makes it possible to 
obtain a nearly unlimited number of variations. It is possible to set up a 
dosing characteristic fufilling the demands for each specific field of 
use, in which cases it is considered not sufficient to supply only a main 
binder for giving the products the desired characteristics. 
Of course it may be necessary that a nozzle, corresponding to the nozzle 
35, is mounted also on the other side of the apparatus shown in FIG. 4 so 
that also the fibre stream at E gets additional binder from said other 
nozzle. Further a nozzle, corresponding to the nozzle 41, may be needed on 
the other side of the apparatus, the left side as shown in FIG. 4, thereby 
influencing the fibre stream A at the position F. Correspondingly a number 
of nozzles, corresponding to the nozzle 35, can be mounted at different 
positions in relation to the fibrillation apparatus, not only at the sides 
of the apparatus but also for instance below or above the apparatus. 
FIG. 6 shows an application of the invention in a so called long chamber 
line. The fibre stream 8 with the binder 44 is brought over the threshold 
45 and into the chamber 46 by the air stream. In the chamber the fibre 
stream 8 descends and the fibres are sucked to the conveyor 47 under which 
a suction box 48 is mounted. The conveyor 47 extends for instance over the 
roller 49, which partly extends inside the chamber 46 over the threshold 
45. The conveyor moves in the direction of the arrow 50. More and more 
mineral wool is deposited on the conveyor 47 so that the thickness 
increases in the direction of the exit 51 of the chamber, where the 
chamber 46 is sealed by means of a roller 53. It can be shown that the 
upper part 54 of the leaving mineral wool layer mainly comes from the 
fibres entering the chamber 46 close to the ceiling 55 thereof and that 
the fibres at the part of the mineral wool layer 56 located closest to the 
conveyor 47 originally come from the lower part of the fibrillation 
apparatus and enter the chamber close to the threshold 45. If it is 
desired to add more binder to any of the surfaces of the product this is 
preferably made at the bottom surface, and the additional binder is 
supplied by means of the nozzle 57 which is supplied with binder over the 
conduit 58. The stream of binder leaving the nozzle 57 meets the lower 
part of the fibre plume 8 and ends, as mentioned above, just in the lower 
part of the product. 
In the above description the nozzles 35, 41 and 57 are mentioned as 
individual nozzles. It is, however, quite possible to use several nozzles 
rather than one single nozzle, and this is often to be preferred so that 
the supply of binder does not become too concentrated within one single 
area. Thus, the nozzle 41 can represent for instance three nozzles mounted 
vertically above each other.