Binding agent for mineral wool and mineral wool product bonded therewith

0001The present invention relates to a bound mineral wool product according to claim 1.

0002For binding mineral wool, in particular rock wool and glass wool, it is known since long to apply a phenol-formaldehyde resin based binding agent onto the fibers, preferably in the dropping pipe subsequent to the defiberizing machine.

0003Hereby the prior art binding agent is preferably sprayed onto the fibers as an aqueous solution or a dispersion, respectively, whereby the phenol-formaldehyde resin is then further polymerized due to still relatively high temperatures of the fibers on the fiber surface and links the single fibers with each other by the polymerization process, in particular at crossing points of fibers, because the fibers lying over each other on a crossing point are quasi embedded there by solidified resin droplets and, therefore, hinder or prevent the displaceability of the single fibers among one another.

0004As is known, mineral wool products are used as a protection against heat, coldness, sound or fire, and are, for the predominant part, classified as nonflammable according to DIN 4102. For this purpose the level of organic - i.e. combustible or smoulderable - material, therefore, needs to be kept at a minimum.

0005Another criterion along with the nonflammability is the mineral wool products' resistance to fire stress, which is of special importance for use of these products as a fire-protection element.

0006As is known, the fire resistance is defined by the period of time by which, upon a particular rise of the temperature on one side of the fire-protection element, e.g. a fire-proof door, the other side of the fire-protection element remains below a defined limit of temperature, for example 180°C. The hold-up time in minutes of the fire-protection element until reaching the temperature limit on the cold side results in the fire resistance class, whereby according to DIN 4102, part 5, the classification for example of fire resistance class T 30 means a hold-up time of 30 minutes, T 60 a hold-up time of 60 minutes, etc.

0007In the past layer structures were used to obtain high fire-protection levels, such as for example in the <patcit id="pcit0001" dnum="DE3824598A"><text>DE-A 38 24 598</text></patcit>, which uses as a fire-protection layer a mixture of a dehydrating hydroxide, such as aluminium hydroxide, and waterglass or silica sol, which is arranged as connective layer between two bodies of bonded mineral wool.

0008The german utility model <patcit id="pcit0002" dnum="DE29507498U"><text>DE-U 295 07 498</text></patcit> discloses a teaching extending the above, which discloses a fire-protection element with a layer structure, which comprises a center layer of inorganic material, which releases water upon influence of temperature and remains dimensionally stable and is arranged between the outer layers of bonded mineral wool as a prefabricated half-stuff.

0009<patcit id="pcit0003" dnum="EP748777A"><text>EP-A-748 777</text></patcit>, <patcit id="pcit0004" dnum="DE4024727A"><text>DE-A-4 024 727</text></patcit> and <patcit id="pcit0005" dnum="US4073849A"><text>US-A-4 073 849</text></patcit> describe binding agents for fibres comprising a thermoplastic resin and a phenotic resin.

0010<patcit id="pcit0006" dnum="EP668391A"><text>EP-A-668 391</text></patcit> and <patcit id="pcit0007" dnum="EP669418A"><text>EP-A-669 418</text></patcit> describe binding agents for glass fibres comprising a polymer mixture and a flame proofing agent.

0011Said prior art has been well approved, but naturally increased layer thicknesses are required, to obtain satisfactory fire resistance levels.

0012If the fire-protection layers cited in the prior art were omitted, then the risk will occur that the mineral wool of the fire-protection element used would become sintered at possible high fire temperatures, whereby-the fire-protection element loses its efficiency relatively fast. On the other hand, it depends on the nature of the used mineral wool by which temperatures sintering of the mineral wool occurs.

0013Hereby especially a mineral wool is of great interest which shows a very low biological durability. The judgement of such mineral wools is defined in the prescriptions of the TRGS 905, which has been. published by the <u>Bundesministerium für Arbeit.</u> Such mineral fibers may become sintered for example at temperatures of above about 700°C.

0014<patcit id="pcit0008" dnum="US5389716A"><text>US 5 389 716</text></patcit> and <patcit id="pcit0009" dnum="US5484653A"><text>US 5 484 653</text></patcit> disclose a binder system for mineral wool products comprising a mixture of a fire resistant latex and an aqueous aldehyde condensation polymer-based thermosetting resin. The fire resistant latex is halogenated and preferably also carboxylated. In addition, the binds system of <patcit id="pcit0010" dnum="US5389716A"><text>US 5 389 716</text></patcit> and <patcit id="pcit0011" dnum="US5484653A"><text>US 5 484 653</text></patcit> disclose flameproofing agents such as ammonium polyphosphates.

0015Therefore, it is the object of the present invention to treat lower melting wool by simple means in such a way, in particular compared to basaltic mineral wool, that insulating materials and fire-protection elements, respectively, are produceable, the fire-resistance of which meets the requirements according to DIN 4102, part 5.

0016The object above is solved by a bound mineral wool product according to claim 1.

0017As at least one thermoplastic homo- or copolymer, that is cross-linkable with phenolic resin, phenolic resin as well as at least one flameproofing agent are incorporated in the binding agent according to the invention, high fire-resistance levels reveal which correspond at least to those, which were obtained with conventional fire-protection elements made of basalt wool.

0018Surprisingly it became apparent that, although organic substances, namely homo- or copolymers cross-linkable with phenolic resin, are added to the binding agent, whereby one skilled in the art would rather expect a deterioration of the fire-protecting behaviour, with for example plates of mineral wool bonded with the binding agent according to the invention having a melting point &lt; 1000°C, e.g. a glass or rock wool having KI ≥ 40 according to TRGS 905, temperatures above 1000°C became possible without sintering or melting the fibers as would have been expected.

0019At present, the mechanism hereof is not yet clear, but it seems, however, without being limited thereto, that decomposition products of the thermoplast cross-linked with the phenolic resin and the flameproofing agent, so-called crack-products, react with the fibers at high temperatures above 500°C, whereby it could be imaginable that carbon is incorporated in or attached to the fibers such that the fibers undergo a chemical conversion.

0020If plates of mineral wool which are bonded with the binding agent according to the invention are produced, serial experiments for classifying the fire-resistance time according to DIN 4102, part 5, reveal that surprisingly high hold-up times of up to 90 minutes are achieved.

0021Important herewith is, that a thermoplastic homo- or copolymer cross-linkable with phenolic resin is used, which then cross-link with eachother on the still hot fibers by being sprayed onto the fibers in the dropping pipe subsequent to the fiber insulation, such that a mixed resin comprising phenolic resin and thermoplastic polymer evolves.

0022Thus, a mixture consisting of thermoplastic homo- or copolymer, cross-linkable with phenolic resin and the phenolic resin, has also importance per se, although it is not part of the present invention, because such a binding agent also exhibits increased temperature resistance without a flameproofing agent and, apart from that, also results in improved properties of the mineral wool, because the brittleness of the total mineral wool product is reduced and, thus, an improved fiber breakage strength in the individual mineral wool products is provided.

0023Particularly suitable as thermoplastic homo- or copolymer cross-linkable with a phenolic resin those according to claim 2 have been approved; here in particular, acrylic resins, polyvinyl acetates, polyurethanes as well as their homo- and copolymers, but especially copolymers based on acrylic acid esters also using acrylonitriles, are excellently suited for the purposes of the present invention.

0024Thus, according to claims 3 and 4, phenolic resins, i.e. the conventionally known phenol-formaldehyde condensation products as well as phenol-urea condensation products or phenol-formaldehyde-urea condensation products, may be used as suitable phenolic resins for the purposes of the present invention.

0025Preferred flameproofing agents according to claim 5, are ammonium polyphosphates.

0026These have been very well approved in practice.

0027Furthermore, additives according to claim 6 may of course be added depending on the intended application of the mineral wool product to be produced.

0028Particularly effective additives for increasing the temperature resistance of bonded fibers, which are free from suspicion of causing cancer according to TRGS 905, e.g. ≥ KI 40, have been shown to be the so-called fiber stabilizers.

0029The known stabilizers china clay and silica sol stabilize the mineral wool fibers and prevent excess shrinkage at high temperatures but, surprisingly, in context with the present invention it was found, that a considerable increased stabilization of the fibers is provided, if metal oxide nanogels and/or ceramic and glass powder, respectively, are added to the binding agent.

0030Due to interaction of the organic substances contained in the binding agent according to the present invention, in particular the thermoplastic polymers, the fibers of rock wool, for example, crystallize at temperatures above about 700°C. The fibers maintain their shape essentially, their surface appears somewhat roughened, and they show themselves as being crystalline in a polarization microsope.

0031This could be a mechanistic explanation for mineral wool KI-40, which is bonded with a stabilizer-containing binding agent, endures temperatures of up to about 1000°C without being sintered or even being melted.

0032It was shown, that stabilizers comprising colloidal metal oxides, especially nanogels and/or ceramic and / or glass particles according to claims 7 to 9, which are added to the binding agent, are particularly advantageous.

0033A further benefit of using fiber-stabilizers according to the claims 7 to 9 is, that the higher the proportion of the stabilizers is the less flameproofing agents are required to obtain the same temperature resistance and fire strength of bound mineral wool products.

0034A preferred embodiment of the present invention uses at least 10 % of phenolic resin relative to the dry mass of the binding agent.

0035The subclaims 11 and 12 represent preferred quantitative compositions of the binding agent used for the present invention.

0036The subclaims 14 to 15 represent preferred embodiments of the mineral wool product of the present invention.

0037Further benefits and features follow from the descripiton of embodiments of the present invention.

Example 1

0038For production of a further binding agent according to the present invention at first the following components were blended to a flameproofing compound: <ul id="ul0001" list-style="none" compact="compact"><li>60 parts water</li><li>65 parts of an ammonium-polyphosphate flameproofing agent</li><li>50 parts of a copolymer based on acrylic acid ester also using acrylonitrile as a thermoplastic polymer cross-linkable with phenolic resin, and then</li><li>175 parts of said flameproofing compound were mixed with 50 parts phenolic resin such that a solids content of about 40 % was provided.</li></ul>

0039After that, this blend was sprayed in a known manner onto the KI 40 fibers in the dropping pipe.

0040Mineral wool plates to be used as fire-protection elements for fireproof doors have also shown in the fire-resistance test to have a hold-up time of at least 90 minutes according to DIN 4102, part 5.