Mineral wool products are used in a variety of forms for insulation purposes, e. g. for fa- cade and roof insulation. Since these products have a very long service life when used for such applications, a problem arises at the end of their service life, e. g. when a house is de- molished-in that no information is available about the manufacturer, the composition, etc. of the mineral wool products, which then constitute waste. However, such information is absolutely essential if the mineral wool product is to be correctly disposed of or recycled.

One aim is thus to apply to the mineral wool products a permanent mark, which can pro- vide information about the manufacturer, composition, etc. From the prior art, methods of marking mineral wool products by providing the finished product with lettering, for exam- ple, are already known. This is done, for example, by sticking on printed paper, film or the like, or by using a colorant for the lettering. The US 5,443,902 describes examples of marking methods in which stickers or stencils are used, or in which cellulose paper is stuck on with glass-fibre adhesive. Another alternative known from the prior art is to burn the mark into the surface of the mineral wool product. In this case, an appropriate means of heating, e. g. a laser, is used to burn a portion of the surface of the mineral wool product,

the mark being formed by the combustion products left behind. This is described, for ex- ample, in the DE 195 42 403.

What all these marking options for mineral wool products have in common, however, is that additional materials which differ from the mineral wool product are present on the surface of the mineral wool product. This has the disadvantage that the foreign substances may limit the range of applications for the mineral wool product. This applies in particular when the marking means applied additionally to the product surface do not satisfy the re- quirements to be met by the mineral wool product, e. g. in respect of flame resistance. The methods described above for the subsequent lettering or marking of the product have the added disadvantage that they are often very costly and, in particular, very time consuming, and that due to the downstream marking facility, the production line is longer.

European patent EP 0928 392 discloses an insulator element mark in the form of an adhe- sive-or plaster-type coating which differs in colour from the mineral fibre layer.

One disadvantage of this system is that this surface layer on the insulator element is only of one colour, and therefore only serves to identify one characteristic. An added disadvantage is that at least parts of the surface of the insulator element are altered by this coating..

Utility model DE 296 03 918 discloses a marking system in which a marker strip with let- tering on the side facing the support element is positioned between the fibre mat and the support material.

This system has the disadvantage that an additional step-making production more com- plex-is needed for printing or lettering the marker strip, or perforating letters in it, at regular distances along the strip. A different marker strip has to be used for each product variant.

Especially with mass products such as insulator element, it is important to have a marking system which is as simple as possible and thus cost efficient.

The object of this invention is thus to provide an appropriately marked mineral wool prod- uct and a method or device for the production of such a product, the undesired presence of a foreign substance on the surface of the finished mineral wool product being largely avoided and, at the same time, the product mark being simple, efficient, reliable and per- manent. The method and the device for producing such a product should likewise be sim- ple and efficient and, in particular, space-saving. In particular, an insulator element of the above-mentioned type should be provided during its production with an uncomplicated and cost-efficient mark which, especially for purposes of material recovery and recycling, can provide information about the properties of the insulator element and its origin. In addition, the mark must be of a nature which fulfils the requirements that apply to the material prop- erties of insulator elements.

This object is established according to the features of the main claims 1,9 and 16. Addi- tional useful embodiments form the subject matter of the subclaims.

Mineral wool products are usually manufactured by generating mineral wool fibres and strands from a molten mineral charge by way of a fiberization unit and a blowing device, and forming the fibres into mineral wool-to which a binder is added-in a blow chamber.

The binder-containing mineral wool is collected as a strip-like blanket on a conveyor de- vice which transports the thus-formed mineral wool blanket into and through a curing oven. In and/or before the curing oven the wool blanket is compressed before the influence of heat on the binder makes the blanket cure in the form of a mineral wool body.

An essential feature of this invention is that the mark is applied to the surface of the min- eral wool product at a stage prior to curing of the mineral wool body, so that when the mineral wool body does cure, the mark is embedded permanently therein. As a result, the finished mineral wool product requires no subsequent processing, and the disadvantage of having to apply foreign substances-used in the prior art for marking-to the surface of the mineral wool product is eliminated. Instead, this invention provides for the mark to be embedded in the mineral wool body in such a way that through subsequent curing of the binder, it is virtually enclosed within the mineral wool body. As a result, the surface of the

mineral wool body is almost uniform and homogeneous, without having any undesirable foreign substances on it.

The mark according to the invention preferably consists of a colorant or of another agent which reacts with the binder, the mineral wool, or with itself during the curing process, thus undergoing a conversion which causes a colour change. The colorant or other agent is applied to the surface zone of the as yet uncured mineral wool blanket by means of im- pregnating, pouring, brushing or the like. Since liquid media of this kind are preferably introduced before the mineral wool blanket is compressed, complete penetration of the liquid medium into the surface zone of the wool blanket is facilitated by the mineral wool's loose, unstructured form.

Alternatively, the mark can take the form of an insert which is pressed into the surface zone of the mineral wool blanket before and/or during compression and curing of the blan- ket. Use can be made, for example, of an already cured and printed mineral wool tape. This method, too, produces a uniform mineral wool body without any foreign substances. In- stead of a printed mineral wool tape it is also possible to use a tape which differs in colour from the mineral wool body and which contains the mark in punched-out form. With this useful alternative, in particular, permanent crosslinking of the insert with the mineral wool body is achieved, together with the formation of a uniform and homogeneous surface, by pressing the tape into the as-yet uncured mineral wool blanket and by the subsequent cur- ing of the binder. To introduce the insert into the mineral wool body, it is preferable to provide an embedding device which contains the insert in rolled-up form in a feed unit, the insert being transferred to the mineral wool blanket by means of a positioning mechanism, e. g. a roll.

Another advantageous way of applying a mark before the mineral wool body has com- pletely cured is to impart a relief surface to the mineral wool body-either before and/or during compression and curing of the mineral wool blanket-by means of embossing ele- ments with a negative or opposing surface structure compared to the intended mark. This can be done, for example in the curing oven, by providing embossing elements on the con- veyor and/or compression unit in the curing oven, e. g. in the form of conveyor panels. The

embossing elements thus impart a relief surface in the form of regularly spaced marks to the mineral wool body while it is in the curing oven. Because the binder cures simultane- ously, the relief surface is maintained permanently.

Alternatively, a relief surface can be incorporated into the surface of the mineral wool body before the mineral wool blanket enters the curing oven. Preferably, the surface em- bossing step is combined with initial compression of the mineral wool blanket before the latter enters the curing oven. This can be effected, for example, by means of a smoothing roll which has on its cylindrical surface a surface structure that corresponds to the mark to be produced. In combination with a compression unit, the smoothing roll can, for example, be designed as one of a pair of opposing rolls located in front of the entrance to the curing oven. As with the embodiment in which embossing elements are provided in the curing oven, the smoothing roll repeatedly applies regularly spaced marks to the mineral wool product. By varying the diameter of the smoothing roll, the distance between the individ- ual marks applied to the mineral wool product can be varied. Since there is a risk that if the surface of the mineral wool blanket is embossed before the blanket has cured the mark may be destroyed again during subsequent processing, it is to advantage if embossing elements located upstream of the curing oven are heated, so that when the embossing elements make contact with the as yet uncured mineral wool, the binder will cure to a certain degree, at least in the surface region. This will provide the surface structure generated by the em- bossing elements with a certain amount of stability for subsequent treatment in the curing oven. Accordingly,. where a smoothing roll is used, the invention provides for this to be heated, for example by having the roll pass a heating element while it rotates. However, all kinds of possible heating means are conceivable here.

Yet another alternative for structuring the surface of the mineral wool blanket before it enters the curing oven is to provide embossing elements having corresponding surface structures on a chain conveyor, which can be located, for example, upstream of an initial compression unit. In this case, too, it is advisable to design the embossing elements such that they can be heated, so that initial curing of the structured surface zone takes place be- fore subsequent processing steps, i. e. compression and curing.

It is to advantage for the mark to comprise letters, numbers, pictograms or other elements that may be depicted, for example bar codes, which can contain relevant information.

The higher the density of the mineral wool product, the more evident the mark according to the invention will be in its surface structure. With densities exceeding 40 kg/m2, therefore, embossing elements inside the curing oven are suitable, since mineral wool products of such density are sufficiently stable to permanently retain the surface structure. For all commonly encountered densities, by way of contrast, the mark is best applied upstream of the curing oven, in particular by means of the other embodiments described here.

According to another solution, at least one set of preferably coloured thread elements is located on and maybe in the insulator element ; it is also possible to use just one thread element featuring all the marking elements in colour (key-word: Mikado). It is expedient to use one or more sets of coloured thread elements on the insulator element. A set of col- oured thread elements is understood to mean at least one thread element but preferably two or more spaced thread elements, each of which is a certain colour. It is also possible for one or more thread elements to comprise differently coloured segments (key-word : Mi- kado).

The thread elements are preferably arranged on one or both of the insulator element's main surfaces. It is also possible, however, to include the thread elements during production of the mineral wool mat, so that they are an integral component of the insulator element.

It is especially useful to arrange the thread elements such that they run in the longitudinal direction of the insulator element. This makes it particularly easy to apply the mark during the production process, as becomes evident from the special embodiment described below.

In particular, the thread elements can be arranged such that they are equally spaced from one another. As a rule, a certain number of colours are specified, including black, white and colourless, which should be easy to differentiate. Combining thread elements in certain numbers or in certain colour sequences provides a means of encoding information such as mechanical and/or physical properties, composition, product name and so on. The infor- mation contained in the insulator element mark can be decoded with the help of a list pro-

vided by the manufacturer, which contains the meaning of the individual colour combina- tions.

To mark an insulator element, one or preferably more, in particular two to six thread ele- ments are used. The scope of the information that can be contained in a set of coloured thread elements increases with the number of threads. Thus a set of x thread elements pro- vides 4x possible combinations and can thus be used to identify 4 different characteristics.

It is especially useful to use four differently coloured thread elements, since this will pro- vide 256 possible combinations. There is no problem in selecting four colours that are easy to distinguish from one another. Besides this, a thread count of four is sufficiently small to permit easy identification. It is by all means possible, however, to use a different number of colours and/or a different number of thread elements in a set.

Since construction materials-including the insulating elements referred to-are used in applications involving differing temperatures that are often far in excess of room tempera- ture, the insulator element's mark must also be of a material which shows temperature sta- bility throughout the service life of the insulator element and beyond. Moreover, insulator elements, for example of glass wool, are generally non-combustible. The properties of the insulating mat and the support dictate the minimum requirements which the material for the mark must satisfy, since otherwise the mark cannot fulfil the intended purposes.

Glass-fibre threads, textile glass yams and twined glass yams are materials that have these properties. These thread elements, in particular, are inexpensive and easy to handle in stor- age.

In addition, one or two sets of thread elements can be affixed to the insulator element in such a way as to provide an orientation aid when the insulator element is being fitted. For example, the upper and lower sides of an insulator element, which are optically identical, can be distinguished by suitable application of a mark.

In a special embodiment, a support is fixed to at least one of the surfaces of the insulating mat or blanket.

The support usually comprises a mesh, a weave or a net. It can be made from various mate- rials, such as metal, plastics or mineral fibres. Usually, the support is in the form of wire mesh, woven wire cloth or wire netting.

The support is fixed to the insulator element mat, which consists of mineral wool or, pref- erably, of rock wool, for example by sewing or quilting it on.

As is shown by reference to a special embodiment, it is technically very easy and thus also cost-efficient to position the thread elements between the mat and the support. The thread elements are simply advanced to the mat or blanket and then clamped between mat and support.

Additional advantages, characteristics and features of this invention become apparent from the following detailed description, which is based on the enclosed, purely diagrammatic drawings.

Fig. 1 is a three-dimensional, partly cutaway view of part of a device for manufac- turing a mineral wool product; Fig. 2 is a three-dimensional, partly cutaway view of another embodiment of a device for manufacturing a mineral wool product ; Fig. 3 is a three-dimensional, partly cutaway view of another embodiment of a device for manufacturing a mineral wool product; Fig. 4 is a three-dimensional, partly cutaway view of another embodiment of a device for manufacturing a mineral wool product ; Fig. 5 is a three-dimensional, partly cutaway view of another embodiment of a device for manufacturing a mineral wool product;

Fig. 6 a) and b) are sectional views through embodiments of the mineral wool products of the invention.

Fig. 7 is a top view of the insulator element.

Fig. 8 shows a device for attaching the mark to an insulator element.

Figs. 1 to 5 all show-in purely diagrammatic form-part of a device or facility for the production of mineral wool products according to this invention. The most important of the parts shown are a curing oven 3, also called tunnel furnace, therein a transport device 4 with interjointed conveyor panels 11 which are passed in an endless loop around the idle rolls 10. Fig. 1 also shows a compression unit 7 in front of the entrance 6 to the curing oven 3. The compression unit 7 consists of two rolls 8 and 9 disposed opposite to each other. Figs. 1 to 5 do not show the following parts of the device for producing mineral wool products: the fiberizing unit, in which mineral wool fibres and strands are drawn from a molten mineral charge; the device with which the fibres and strands-drawn to wool-have a binding agent applied and are collected in the form of a mineral wool blan- ket 1 on a conveyor belt. On the contrary, all the drawings (Figs. 1-5) only show the min- eral wool blanket once it is in position on a conveyor device such as a loop conveyor belt.

The fiberizing unit and the device for adding the binder and collecting the binder- containing mineral. wool into a mineral wool blanket are not shown in Figs. 1-5 because they do not differ from the standard equipment described in the prior art.

The essential feature of the embodiments according to the invention is to be seen in the fact that a marking device is provided in the area of the curing oven 3, the compression unit 7, or upstream thereof.

According to the embodiment of Fig. 1, the marking device is part of the conveyor de- vice 4 in the curing oven 3, and is designed such that the conveyor panels 11, so-called flights, which are interjointed to form a loop conveyor belt, have a surface structure 18 which complements the structure required as mark 20 on the finished mineral wool body 2.

In the embodiment shown, the mark 20 takes the form of the lettering"ISOVER", by way of example. However, any other kind of mark, e. g. pictograms, numbers, bar codes or the like is conceivable..

The mineral wool product 2 is marked by the device according to the embodiment of Fig. 1 in the following way: as the mineral wool blanket 1 passes through the curing oven 3, the surface structure 18 of the conveyor panels 11 is imprinted in the surface of the mineral wool blanket as it cures, so that surface impressions and/or incisions are left which give the fully cured mineral wool product 2 a relief surface. To this end it is preferable if the sur- face structure 18 and the conveyor panels 11 in general are of perforated design, because in order to cure the binder, hot air is blown from underneath up through the conveyor panels 11. The relief surface represents the mark 20, since when the marked surface of the mineral wool product 2 is exposed or viewed appropriately from the side, the relief surface throws a shadow which produces a visible mark 20.

In another embodiment, shown in Fig. 2, a relief surface serving as mark 20 is likewise formed on the finished mineral wool product 2. In this case, however, the surface of the mineral wool blanket 1 is not structured by embossing the blanket 1 with the conveyor device 4 in the curing oven 3, but earlier on, while the mineral wool blanket 1 is being compressed prior to reaching the entrance 6 to the curing oven 3. To this end, a marking device is provided as part of the compression unit 7, which precompresses the mineral wool blanket 1 before it enters the curing oven 3. In the embodiment shown, the compres- sion unit consists of a pair of spaced rolls 9 and 12, which, by means of the space between them, determine the thickness of the mineral wool blanket 1. The roll 12 located on the side of the mineral wool blanket 1 to which the mark 20 is to be applied has on its cylindri- cal surface a surface structure 17 which again complements the mark 20 to be produced in the mineral wool blanket 1. Roll 12 also has a heating means (not shown) and can thus be heated. When the mineral wool blanket 1 passes through the compression unit 7, the sur- face structure 17 is pressed into the surface of the mineral wool blanket 1, producing corre- sponding depressions therein. At the same time, the heating means heats roll 12 to a tem- perature which causes initial curing in the surface zone of mineral wool blanket 1, so that the depressions made in the surface of the mineral wool blanket 1 by the surface structure

17 of roll 12 are fixed. The reason for this is that the hot roll 12 causes the binder to cure in the surface zone, thus immobilising the mineral wool fibres and strands in the position they have assumed; the large number of points within the mineral wool at which crosslinks have formed prevent any further free movement of the mineral wool fibres and strands. To shape the thus pre-treated mineral wool blanket 1 with the at least partially cured surface layer or skin on one side into the final mineral wool product 2, the mineral wool blanket 1 may then undergo additional compression before it is cured in a curing oven 3.

Fig. 3 shows an alternative embodiment of the device according to the invention for the production of mineral wool products; this embodiment includes a marking device 13 which is provided in addition to the compression unit 7 and the curing oven 3 and which is lo- cated upstream of these in the zone from which the mineral wool blanket 1 is fed towards the curing oven 3. The marking device 13 comprises a chain conveyor with a loop con- veyor belt 16 which is guided around two idle rolls 14 and 15. On chain belt conveyor 16 embossing elements 27 are provided which in turn have a surface structure that comple- ments the mark 20 to be applied to the mineral wool product 2.. The embossing elements 27 generate depressions and incisioins on the surface of the mineral wool blanket 1, and these are again fixed by virtue of the fact that the heated chain belt conveyor 16, or at least the heated embossing elements 17, cause at least a restricted surface zone of the mineral wool blanket 1 to cure, as was the case in the embodiment of Fig. 2. However, according to the embodiment of Fig. 3, unlike that of Fig. 2, the mineral wool blanket lwith its at least partially cured surface relief is pre-compressed by compression unit 7 in a subsequent, in- dependent step. In the embodiment of Fig. 3, therefore, the marking device 13 and the compression unit 7 are independent and separate components of the device according to the invention for producing mineral wool products.

Fig. 4 shows yet another embodiment, in which, as was the case in the embodiment of Fig. 3, the marking device 19 is located upstream of the compression unit 7 and the curing oven 3, in the zone from which the mineral wool blanket 1 is fed towards the curing oven 3. However, this embodiment differs from that of Fig. 3 in that the marking device 19 does not generate any depressions or incisions in the surface zone of the mineral wool blanket 1, but is a spraying device which sprays-via spray nozzles 21-a marking agent onto the

surface of the mineral wool blanket 1 to be marked ; the marking agent may be a colorant, for example, or an agent which becomes a marking agent by reacting with the binder or with the mineral wool or by undergoing a phase change. Since the binder has not yet cured at this stage, and the mineral wool has not yet been compressed, the agent sprayed onto the surface can very easily penetrate into the mineral wool and be deposited in areas close to the surface. As a result of subsequent compression and curing of the mineral wool blanket 1, the added agent is practically enclosed in the finished mineral wool product 1. The mark 20, however, is still clearly visible. To ensure clearly defined and localised application of the marking agent to the mineral wool blanket 1 it may be helpful to additionally insert a stencil between the spray nozzles 21 and the surface of the mineral wool blanket 1. A stencil of this kind has not been depicted in the embodiment shown. If the spray is applied at regular intervals to the mineral wool blanket 1 passing underneath, regularly spaced marks will be produced thereon.

Another form of marking device 23 located upstream of the compression unit 7 and the curing oven 3 is shown in Fig. 5. In this case, the marking device 23 consists of a feed mechanism 24 and a positioning mechanism 25. The feed mechanism 24 comprises a ro- tatable reel onto which an insert 26 to be embedded as mark 20 in the mineral wool prod- uct 2 is wound. In the embodiment shown, the positioning mechanism 25 is a roll 25 with which the insert 26-in the embodiment shown a mineral wool tape printed with the mark -is positioned on the surface of the mineral wool blanket 1. The insert 26 is pressed by the downstream compression unit 7 into the mineral wool blanket 1 and subsequently, during curing in the curing oven 3, forms firm crosslinks with the mineral wool by way of the binder. Instead of printed mineral wool tape it would also be conceivable to use a coloured tape-for example black tape-which has the marks in punched-out form.

Each of the two parts a) and b) of Fig. 6 show a cross-section of a mineral wool product 2 according to the invention, in both cases with a mark 20 on one side of the product 2. The mineral wool product 2, the body of which has an essentially rectangular cross-section, has a surface layer 22 surrounding the entire mineral wool body. The surface layer 22 is char- acterised in that it forms the boundary layer between the mineral wool fibres and strands on the one hand, which are firmly crosslinked in the mineral wool with the binder, and the

surrounding medium on the other hand. Unless it is scrutinised microscopically, the surface layer 22 is seen to have an essentially dense and smooth surface. As shown in Fig. 6a, the marked side of the mineral wool product 2 has depressions and incisions which are clearly recognisable against the essentially dense and smooth surface; the surface layer 22, how- ever, is continuous, i. e. dense and smooth, along the depressions and incisions. This is ex- plained by the fact that the final compression and curing of the mineral wool blanket and thus also of the surface layer does not take place until after or, at the earliest, during the structuring of the surface of the mineral wool blanket 1 (Fig. 6b).

The same applies to the embodiments in which the mark is produced by means of an added marking agent or a marking agent which is formed during curing, or by means of embed- ding an insert 26. Here too, the mark 20 is firmly incorporated in the surface layer 22 or directly beneath it, the surface layer 22 remaining smooth and dense. This means that there are no troublesome foreign substances on the outside of the surface layer 22 and thus out- side the mineral wool body 2.

Figure 7 shows an insulator element 1'which consists of a mineral wool mat 2'and a wire- mesh-like support 3'that is fixed to the mat by stitching. In the lower section of the insu- lator element shown, four coloured twined yarns 4', 5', 6und 7'can be seen located be- tween the mat 2'and the screen-like support 3'. Each of the four threads shown in this em- bodiment can have one of the colours red, blue, yellow or black. Information about the product-for example, information about the manufacturer, the product name, and physi- cal and mechanical properties of the insulator element-are encoded in the sequence of colours of the threads 4', 5', 6'and 7' (e. g. blue-blue-black-red). Details as to what in- formation the different colour combinations stand for is provided by the manufacturer to whoever is recovering and recycling the insulator elements.

Figure 8 shows diagrammatically how the threads 4', 5', 6'and 7'are inserted between the mat 2'and the support 3'.

In the standard production process, the mineral wool mat 2'is advanced in the direction of the arrow via a roll 8'. The material for the support 3', in the form of a wire mesh, is ad-

vanced to the mat 2'via the roll 8'and fixed to the mat by means of a unit 9', for example a stitching device.

In addition, the coloured threads 4', 5, 6'and 7'serving as the mark, which are rolled up on reels 10, are fed between the mat 2'and the support 3', between which they are clamped.