EP0000402A1 - Process for the manufacture of insulating construction boards - Google Patents

Abstract

In the production of insulating plates, a mineral fiber plate pre-bonded with an organic binder with a density of at least 0.15, preferably 0.2 g / cm 3 with an aqueous slurry of a binding clay, the particle size of which is at least 80%, preferably 90% below 2 µm and which splits off its chemically bound water in the temperature range from 400 to 650 ° C, completely soaked, then dried at temperatures above 105 ° C, preferably by microwave radiation, and after drying at temperatures above 400 ° C, but below the transformation temperature of the one for the production The mineral fibers used in the pre-bound mineral fiber board are preferably annealed in a reducing atmosphere. It is advisable to use a binding clay that consists of the following minerals:

The impregnated plate can be subjected to another impregnation locally, preferably at its edges, before drying.

Description

The invention relates to a method for producing insulating building boards and is based on a method in which a mineral fiber board prebound with an organic binder on a plastic basis is impregnated with an aqueous slurry of an inorganic binder and then warm-dried.

Insulating plate should generally be understood to mean a heat and / or sound insulating plate which can also be used as a fire protection plate if necessary.

In such a method, for example has become known from US Pat. No. 3,551,276, find suspensions of clay mineral substances, such as bentonite and / or kaolin or ball clay in combination with boric acid, for impregnating glass fiber felts pre-bound with phenolic resins or water glass or with colloidal SiO _2, or - plates with densities from 0.08 to 0.14 g / cm 'use. In addition, inert fillers in the form of prophyllite and water repellents, predominantly based on silicone, can be added to the inorganic binders. The glass fiber bodies impregnated in this way are dried and cured at temperatures between 218 and 288 ° C.

A similar process can also be found in DT-AS 1 619 131. The known processes particularly aim to produce mineral fiber products with high temperature resistance. According to the teaching of US Pat. No. 3,551,276, a hydrophobizing agent based on silicone can be added to the impregnating binders consisting of bentonite, kaolin and / or ball clay and boric acid, the impregnated molded body then being dried at about 240 ° C. This addition then serves to achieve sufficient moisture resistance of the products.

However, such insulating boards have only a limited area of use because they do not have the high mechanical strength that is generally required. Insulating building boards with the required high mechanical strength values can only be produced in the form of asbestos silicate boards, whereby asbestos fibers, hydraulic cements or calcium hydroxide with the addition of quartz powder or other silicate substances are first mixed with water to form a mash. This slurry is then dewatered and the filter cake thus obtained is pressed and hydrothermally hardened. The bending strengths of such plates are between 50 and 100 kp / cm 'at plate densities of 0.65 to 0.8 g / cm'. The compressive strengths are in the range from 30 to 70 kp / cm ² .

However, such plates have serious disadvantages. Since such plates are generally machined, i.e. sawn, milled or sanded, this process releases very fine asbestos fibers into the air, which are harmful to health because they can cause cancerous diseases of the respiratory tract. In some countries, the use of such insulating boards is therefore already prohibited.

In addition, these plates do not lead to sufficient temperature resistance because the calcium hydrosilicate used only has a temperature resistance of approx. 400 ° C. At higher temperatures, the mechanical strength of such insulating building boards decreases and cracks can form in the board.

Finally, these plates also contain a considerable proportion of water-soluble, in some cases strongly alkaline, substances, so that the effect of moisture can lead to salt efflorescence on the surface of the plates.

According to US Pat. No. 2,717,841, the prior art also includes a method for producing an insulating plate for wall and ceiling constructions with flame-retardant properties. According to this method, a glass fiber layer pre-bonded with a plastic binder with a density of 0.11 g / cm ^{3 is} first impregnated with an inorganic binder slurry consisting of hydraulic cements or gypsum, but preferably of magnesium oxide chloride cement (Sorel cement). After the excess of the binder suspension has been suctioned off, the moist plate is dried at 232.degree. The product obtained has a density of 0.28 to 0.3 g / cm ^3. The density can be increased up to a value of 0.5 g / cm ³ . However, this plate also does not meet the requirements that an asbestos silicate plate already achieves in terms of compressive and flexural strength.

The invention seeks to remedy this. The invention, as characterized in the claims, solves the problem of specifying a method by which it is possible to exceed the compressive and flexural strength values of asbestos silicate boards without accepting the negative properties of the asbestos fiber boards bonded with cement to have to.

In the method according to the invention, a mineral fiber board bound with organic binders is deliberately used, the density of which is already selected to be as high as possible. This leads to the advantage that this plate already has good dimensional stability during the impregnation and drying process activity receives. In addition, such a high degree of compaction of the starting fiberboard, due to the favorable ratio of fiber content to binding clay, has a particularly advantageous effect on achieving the required strength properties of the end product, which not only has excellent compressive and flexural strength, but also an outstanding splitting strength. Another advantage results from the fact that the elastic modulus of this product is influenced favorably.

• - das Bindevermögen des Tones muß, damit die geforderten Plattenfestigkeiten erreicht werden können, sehr hoch sein, die Trockenbiegefestigkeit des Bindetones sollte, gemessen nach DIN 51030, nicht weniger als 30 kp/cm² betragen;
• - der Restkornanteil von 10 bis 20 Gew.-% darf nicht mehr als zur Hälfte über 15 µm liegen;
• - das Strukturwasser, das als OH-Gruppen im Kristallgitter des Tones eingebaut ist, muß im Temperaturbereich von 400 bis 600°C abgespalten werden. Dadurch verliert der Ton seine Redispergierbarkeit in Wasser und die Tonbindung in der Platte wird wasserunempfindlich.

The binder clay used for the impregnation of the mineral fiber board, which must have a small grain size of at least approx. 80%, preferably 90% by weight below 2 gm, is expediently selected according to the following criteria:

• - The binding capacity of the clay must be very high so that the required plate strengths can be achieved, the dry bending strength of the binding clay, measured according to DIN 51030, should not be less than 30 kp / cm ² ;
• - The residual grain fraction of 10 to 20% by weight must not be more than half over 15 µm;
• - The structural water, which is incorporated as OH groups in the crystal lattice of the clay, must be split off in the temperature range from 400 to 600 ° C. As a result, the clay loses its redispersibility in water and the clay binding in the plate becomes insensitive to water.

After a series of investigated clay mineral substances, fine and colloid clays from secondary deposits have proven to be the most suitable.

These clays preferably consist mainly of the following minerals:

The chemical composition of the clays fluctuates in the range of the following weight fractions:

The thermal treatment provided according to the invention in the range between 400 ° C. and the transformation temperature of the mineral fibers used for the production of the prebound mineral fiber board achieves a complete water resistance of the insulating building board. At the same time, the flammable organic constituents in the form of resins, lubricating oils, wetting and dispersing aids are removed by the temperature treatment medium in the manufacture of the mineral fiber base plate or impregnation process with the clay suspension have got into the plate, largely driven out again.

The end product can not only no longer ignite, but also no longer glow and can therefore be regarded as an absolutely non-flammable material according to DIN 4102.

Preferably, in the process according to the invention, the starting material for the mineral fiber board is one with a maximum fiber diameter of 6 nm. When using coarser fibers with a diameter of more than 6 ₄ m, the clay suspension can be introduced more easily into the fiberboard, since the fiber cavities in the plate are relatively large and therefore, even when using coarse-grained clays when impregnating such a plate, there is no fear of a filter effect However, the final strengths achieved, in particular the splitting strength of a mineral fiber board produced in this way are considerably lower than in the case of a comparable board whose starting material consists of finer fibers. The reason is probably to be seen in the fact that coarse fibers in the production process of the starting plate are deposited much more in layers than is the case with fine fibers, and the degree of matting of coarse-fiber layers with each other is much worse than with plates made of finer fibers.

It has been shown that the temperature treatment between 400 ° C and the transformation temperature of the pre-bound for the production Mineral fiber board used mineral fibers a remarkably high increase in the compressive and bending strength values and the elastic modulus of an average of 30 to 45% compared to the values that did not occur in the heat-treating boards.

It was also found that this unexpectedly high increase in strength can only be determined when temperatures below the transformation point of the mineral fibers used to produce the starting plates are used. In the basalt fibers selected as the exemplary embodiment, this transition temperature was 620 to 640 ° C. If this temperature was exceeded, there was a significant deterioration in the panel strength, particularly with regard to flexural strength and elasticity behavior.

This reduction in the strength properties is due to the fact that due to oxidation of the mineral fibers, during which a conversion of the FeO present in the fibers into Fe ₂ 0 ₃ takes place, the fibers become largely embrittled and thus the actual function of the fibers as a scaffold of the building board to give a high bending and tensile strength and elasticity is lost. The conversion of iron oxide under the influence of atmospheric oxygen is strongly temperature-dependent and proceeds particularly intensively when the transformation point is reached, at which the fiber softens.

This undesirable oxidation reaction in the treatment of mineral fiber plates filled with binding clay in the temperature range mentioned can be In a further embodiment of the invention, this is practically completely eliminated if the temperature control and dwell time are further adjusted so that, on the one hand, the crystal water is almost completely eliminated from the binding clay and, on the other hand, the carbon, which is the residue from the combustion of the organic constituents in the Temperature treatment between 400 and 650 ° C forms, is not yet completely burned out. This phenomenon can be further improved by the fact that the temperature treatment in this temperature range takes place in a reducing atmosphere, that is to say by appropriately setting the flame in the case of furnaces operated with gas or heating oil, or by installing a vessel with powdered graphite or graphite rods in the furnace chamber when using electrically heated ovens.

In a further embodiment of the invention, the impregnated plate can be subjected locally to another impregnation before drying, this additional impregnation advantageously being carried out at the edges of the plate. In the area of double impregnation after drying and heat treatment at temperatures above 400 ° C, but below the transformation temperature of the mineral fibers used for the production of the pre-bonded mineral fiber board, reinforced areas are obtained which are used for picking up nailing, milling grooves and working out springs or tines and the like, can serve. In this way, you can make shapes in particular at the edges, which allow the direct connection of one plate with the subsequent plate and a complete seal of any gaps and also the Increase the strength of such a composite panel.

If one proceeds in a further development of the invention from a double-strong plate and splits it into two plates after soaking, drying and tempering, two plates are obtained, each with a smooth and a rough surface. The smooth surface can be wallpapered immediately, while the rough surface can be plastered well. In this way, a panel is created with two options for surface cladding, which is of particular advantage in construction.

Starting from an at least approximately double-strong plate, the same can be split into two plates before soaking, and this gives the advantage that the impregnation process, provided that the gap side comes up when soaking, is facilitated.

Finally, in a further embodiment of the invention, drying can be carried out by microwave radiation. This avoids a drying gradient from the outside in, which inevitably occurs, for example, when drying with warm air. Rather, drying is achieved from the inside out and thus a uniform structure of the finished plate.

The invention will be explained in more detail below with the aid of exemplary embodiments:

Example I

In a basalt mineral fiber sheet with a width of 120 cm and with a weight per unit area of 5 kg / m ³ , an aqueous phenol-formaldehyde resin solution with a solids content of 4.5% by weight was uniformly sprayed in using the shaft method. The amount of binder sprayed was 4.2 kg / m ² .

The moist fibrous web was then pressed in a plate machine between two perforated metal strips to a thickness of 25 mm to form a plate and at the same time dried and cured with hot air at 200 to 220 ° C. The plate thus produced had a density of 0.2 g / cm ³ . The resin content was 3.6% by weight of solid, based on the weight of the plate.

Immediately after leaving the plate machine, the strand of plates thus produced was passed into a flooding device, where an aqueous suspension of binding clay was sucked into the mineral fiber plates from above with the aid of a vacuum applied to the underside of the plates, until the plate was completely saturated. The impregnated plate was then passed on a conveyor belt into a drying oven and dried there with circulating air at 200 ° C. It was then heated for 10 minutes at 580 ° C. or 20 minutes at 480 ° C. in an oven heated with natural gas with a reducing flame.

Example II

A mineral fiber plate pre-bonded with resin, which was saturated with the binding clay suspension, was passed over a suction box before drying, where the excess binding clay was removed from the fiber cavities of the plate by applying negative pressure. Otherwise the procedure was as in Example I.

Example III

The plate saturated with binding clay suspension was passed between two pressure rollers, the excess of the clay suspension being almost completely pressed out of the plate.

Otherwise, the process was carried out according to Example I.

When carrying out the process according to Example II and Example III, the amount of water to be evaporated when drying the plates could be reduced considerably and the drying time could be shortened considerably.

In all three exemplary embodiments, the binding clay suspension used was prepared in a turbo mixer by slurrying a powdery or lumpy binding clay of type FC from Didier from Gruenstadt in water. The viscosity of the suspension was adjusted to 6 to 12 cP by adding sodium polyphosphate salts as liquefying agents.

• - in Abhängigkeit von angestrebten Raumgewichten des Endproduktes
• - in Abhängigkeit davon, ob nach dem Auffüllen der Platte mit der Bindetonsuspension der Überschuß aus der Platte abgesaugt werden sollte oder nicht.

The solids concentration of the suspension was between 15 and 60% by weight and was chosen:

• - Depending on the desired density of the end product
• - Depending on whether the excess after filling the plate with the binding clay suspension should be sucked out of the plate or not.

Table 1 shows a compilation of different process procedures and the achievable or achieved values, whereby a detailed description of this table is not necessary because of the detailed information of the process steps and the corresponding values.

Claims (10)

1. A process for the production of insulating boards, in which a mineral fiber board prebound with an organic binder based on plastic is impregnated with an aqueous slurry of an inorganic binder and then dried warm, characterized in that starting from a mineral fiber board prebound with an organic plastic binder having a density of at least 0.15, preferably 0.2 g / cm ³ , this mineral fiber plate with an aqueous slurry of a binding clay, the particle size of which is at least 80%, preferably 90% below 2 μm and which is in the temperature range from 400 ° C. to 650 ° C. splits off its chemically bound water, completely soaks and after drying at temperatures above 105 ° C at temperatures above 400 ° C, but below the transformation, formation temperature of the mineral fibers used for the production of the pre-bound mineral fiber plate. 2. The method according to claim 1, characterized in that one with a maximum fiber diameter of 6 microns is used as the starting material for the mineral fiber board. 3. The method according to claim 1 or 2, characterized in that the tempering process is carried out in a reducing atmosphere. 4. The method according to one or more of the preceding claims, characterized in that the binder clay used mainly from the following Minerals

5. The method according to claim 4, characterized in that the composition of the binding clay used is in the range of the following parts by weight:

6. The method according to one or more of the preceding claims, characterized in that the impregnated plate is locally subjected to another impregnation before drying. 7. The method according to claim 6, characterized in that the repeated impregnation is carried out at the edges of the plate. 8. The method according to one or more of the preceding claims, characterized in that from a double strong plate and this is split into two plates after soaking, drying and tempering. 9. The method according to one or more of claims 1 to 8, characterized in that a double-strong plate is assumed and this is split into two plates before soaking. 10. The method according to one or more of the preceding claims, characterized in that the drying is carried out by microwave radiation.