DE2606487A1 - Material for filtration, sealing or insulation at high temp. - made from suspension of inorganic fibres loaded with silica gel - Google Patents

Abstract

Mouldings are continuously prepd. from inorganic fibres, esp. of ceramics, asbestos, minerals, slag, basalt and/or glass, in parent patent, the fibres opt. being mixed with organic fibres, the prepn. employing a reduced pressure. In the addition, the fibres are subjected to extensive disentanglement, pref. by agitation in air, and then ionically adjusted to a neutral pH, loaded with silica gel, pptd. with anionic starch, and the homogeneous dispersion poured continuously onto a transporter sieve, followed by overhead dehydration using reduced pressure to form a continuous sheet without using heavy pressure rollers, after any shaping which may be required, the material is dried. Sheet is produced 25 mm thick or thicker, suitable for mouldings resistant to high temp. and employed for insulation, sealing, or filtration.

Description

Process for the continuous production of molded parts

inorganic fibers The invention relates to a method for continuous Manufacture of molded parts from inorganic fibers, especially ceramic fibers, such as oxide fibers or aluminum silicate fibersN but also e.g. asbestos, stone, slag, Basalt or glass wool, individually or in a mixture with one another, possibly also in a mixture with organic fibers, using a vacuum on a transport sieve, e.g. a cardboard machine, preferably without a counter pressure roller (format roller). Included you can in particular mineral fiber webs of any thickness up to and over 25 mm received.

Insulation, sealing and / or filtering materials based on of inorganic fibers are in different embodiments according to different Methods made. The temperature resistance depends primarily on the melting point of the fibers, while the insulation ability mainly depends on the specific gravity or density not only of the fibers, but also of the Density of the molded body produced is determined. Molded body from loosely laid, in some way bound or quilted fibers indicate relatively low specific weight, but good insulation properties, however, they have the disadvantage that they have a low inherent strength to have.

Are the fibers solidified to a large extent or with each other connected, as is the case, for example, in the asbestos industry in the manufacture of Asbestos paper and / or cardboard is done using the conventional Hatschek method, when it is carried out using concentric format rollers, many thin ones If layers are pressed onto one another, the strength increases, but it does so also the specific weight or the density. Deteriorates with increasing density the insulation effect, since the layers pressed against each other increase the thermal conductivity is increased.

The same applies to very temperature-resistant inorganic fibers, especially synthetic fibers, such as silicate or oxide fibers, what means that their excellent high temperature resistance to impact of temperatures of more than 10000C when using the above Methods for isolation purposes does not apply.

To make high-temperature-resistant fibers into molded parts with good insulating properties and high intrinsic strength while avoiding the disadvantages described above to process, one has gone over to the fibers from an aqueous slurry, which optionally contains additives of organic or inorganic binders Applying a vacuum, i.e. by means of a suction effect, to solidify.

For the production of plates, cones, pipes, bowls or the like the fibers are sucked from an aqueous slurry into a mold. The mold itself is connected to a vacuum device. There will be more or less regularly the fibers on the mold surface with the formation of molded parts distributed and solidified. When performing this method, which the Form is mostly immersed into the fiber liquor from above, there are deviations in the layer thickness and the specific weight of the molded parts are unavoidable.

Panels are mainly produced in the manner described.

With this method, there are limits to their size, which are around 500 x 1000 mm with a panel thickness of about 5 to 25 mm.

The greater the thickness and size of the panels, the greater the density differences to.

Another disadvantage of this known method is that it can only be carried out discontinuously. Furthermore, there is fiber depletion the fiber liquor in the containers is a problem. This fiber depletion or degradation the concentration of fibers per volume of the liquor causes irregularities of the molded parts produced. The production output produced molded parts per unit of time) is also minor when performing this method.

The invention has therefore set itself the task of providing a method for to create continuous production of molded parts from inorganic fibers, which does not adhere to the disadvantages outlined above. This task is carried out at the process of the type described at the outset is achieved by a fiber liquor continuously in homogeneous distribution on a transport sieve and dewatered by vacuum creating an endless fiber web that can be transported further, from which individual pieces with the desired size are cut off, which optionally further deformed, preferably still in the green state.

The dissolution of the fibers and the homogeneous distribution with formation a fiber liquor can be in large containers, for example from 4 to 6 m3, under Stirring can be carried out, for example in a "pulper". Preferably served one is so-called "Buftrührer", which are very susceptible to breakage Gently break down synthetic fibers and distribute them homogeneously in the fiber liquor. Synthetic fibers are particularly prone to breakage, which result from the melt flow of silicates, Quartz, metal oxides, glass, basalt, kaolin or the like have been produced.

Of particular interest are those that are still temperature-resistant Fibers based on aluminum oxide or aluminum silicate, such as those found under under the name Kaowool are on the market, without any foreign fibers, as they are based on them Way, the temperature resistance of these products can be used particularly well can.

Asbestos can also be used to create very loose, specifically light but dimensionally stable Lay fleeces. In the case of rock wool, slag wool, and glass wool, the fibers are preferred either in short-cut form, for example in a length of 2 to 3 mm used, or the digestion with a ttSuftrührertt is carried out for a long time, so that a particularly good loosening with partial foaming of the liquor is achieved. Here are also foaming agents, which of course are general can be used of particular interest, for example surface-active Agents or gas-generating agents.

The dehydration is preferably carried out in such a way that the vacuum is kept almost the same or even gradually increased. Through the Increasing drainage of the fiber web is known to be the resistance of the web against the passage of air from above into the suction box always less, so that with the same Suction power in all suction boxes the vacuum from suction box to suction box is lower will. In practice, the vacuum level or an increase in the vacuum level can be maintained Way to be carried out that under the transport sieve flat vacuum boxes with increasing vacuum power can be arranged. The number of stitches of The transport sieve is preferably chosen in such a way that neither the fibers pass through too much water passes through before the vacuum is applied. It are suitable basically screens such as those used in asbestos cardboard manufacture, whereby Bronze sieves or plastic sieves can be used.

Furthermore, the vacuum is preferably at a distance from the run-up point applied to the fiber liquor, for example at a distance of 3 to 5 m of the sieve depends essentially on the downstream dryer output. The thickness of the web is set on the headbox.

The sieving speed is, for example, approx. 1 m / min at 1800C Dryer temperature and a dryer duct length of approx.

20 metres. The concentration of the fiber liquor is about 0.5 to 4 % By weight, in particular 1 to 2% by weight, depending on the desired thickness of the web. As functional The addition of a binder has proven to be particularly useful for all mineral fibers the use of about 40% silica sol, which is in an amount from 0 to 6%, in particular 2 to 6%, based on fiber weight is added, depending on which Hardness of the finished web is desired. A gas propellant can also be used to support the loosening up. When it is used, the Amount expediently 0.1 to 1% by weight, based on water, in particular about 0.4% by weight.

Basically, no counter-pressure or format roller is used to not to compact the web in the usual way. You can, however, on the top of the fiber web during dewatering one roller or more rollers with little Let the contact pressure take effect. In doing so, not only is the water drain, but also the formation of a flat surface and the achievement of a uniform one Thickness and thus density of the molded part promoted.

The lateral limitation of the endless fiber web is done by letting it run along for example, 5 to 10 cm thick and 6 to 8 cm wide soft rubber belts. To the Prevent the transport sieve from sagging at appropriate intervals Carrier rollers provided. The web width is, for example, 2.10 m the fiber web produced can be adjusted by adjusting the concentration accordingly and / or amount of the fiber liquor running up on the transport sieve and / or through the speed of the sieve can be regulated.

According to the invention it is possible to use fiber webs with a width of more than 2 m and different thicknesses.

About irregularities in the fiber liquor running onto the transport wire With regard to the concentration of the fibers, the liquor is removed from the digestion tank fed to the sieve via, for example, 3 to 5 overflow and underflow baffles. Included adjustment wheels allow differentiated height adjustment for the fleet and underflow.

The fiber web produced is preferably down to a dry content dehydrated from 30 to 55 e. Sheets are cut out of the web that are not are further deformed, so you can also dewater to higher dry contents carry out. If the parts cut off from the sheet are then further deformed, then a lower dry content of approx. 25 to 35% is more favorable.

Preferably, the fiber liquor fed to the transport screen gas propellants and / or binders added in the usual amounts. As a binder A: 4 above silica sol is preferably used.

The "green" fiber web produced in the manner described above is in a downstream drying oven, which is set to 160 to 2000C, for example or above is set to dry. After leaving the drying oven it will show the material has a moisture content of less than 1% and can be cut in any way will.

The fiber web can also be narrowed before passing through the drying oven Tracks are cut by means of a circular knife, knurled wheel or the like. The outer edges of the "green" web can be trimmed in front of the drying oven. The side trimming before going through the furnace has the advantage that the resulting Wet waste added to the next liquor batches without affecting the recipe can be.

The green fiber web can be formed, for example, by the Sieve is guided over moving, for example curved documents or otherwise receives a shape deviating from the flat shape. For example, if part of the (cut) web over a semicircular in the transverse direction of the screen Sieve profile guided, you get endless half-shell-shaped pipe insulation, which in this form can be dried and thus solidified and the before or after can be cut into any length after drying. From the "green" fiber web pieces of any size can of course be cut out or punched out, which, as already mentioned, by suitable deformation of the screen itself or by On or in additional compression or suction molds to form parts with the desired Configurations can be shaped.

That way you can. z.3. also slider for liquid Metals, insulation bodies for heat spirals or the like or, for example, hemispherical ones or form spherical segment shapes and manufacture them in a fast work cycle. The so generated Molded parts are then placed in the drying oven dried and solidified.

The check and test values are shown below in tabular form a test plate produced by the method according to the invention with a thickness of 5 mm as well as one according to the discontinuous process described at the beginning produced test plate with the same thickness: continuous discontinuous Process Process Loss on ignition 4 - 5 * 8 Shots content 21.7% 24% Tensile strength 5.7 kg / cm2 2.25 kg / cmZ compressive strength 1.51 kg / cm2 0.7 kg / cm2 ball indentation hardness 50-70 / 100 30-70 / 100 Density 200-230 kg / m3 190-240 kg / m3 The invention enables manufacture an endless fiber web with the same layer thickness and the same specific weight as well as the same mechanical strength values. It can be very fragile Use high-temperature-resistant inorganic fibers, for example from melt flow manufactured fibers, with molded parts with good insulating properties and high mechanical properties Intrinsic strength can be obtained. With regard to the larger than paper fibers Length of the fibers used according to the invention, their higher specific weight as well as their greater susceptibility to breakage and their more difficult ones Entanglement, it was surprising that the inventive method in the outlined can be carried out in a simple manner and molded parts with the desired properties mentioned supplies. The density of the molded parts produced according to the invention can be up to 0.25 g / cm3 without losing the inherent strength.

Fiber materials include, for example, fibers made from kaolin, aluminum oxide, Zirconium oxide, quartz, basalt or mixtures of such fibers in question, which optionally can also contain organic fibers. That according to the invention is of particular value Process also for the production of asbestos panels with a specific weight from 0.4 to 0.6 g / cm3, which was previously used as an insulating material according to the Hatschek method produced insulating panels with higher density. As already mentioned glass fibers, basalt fibers or slag wool can also be used for production of molded parts, also if necessary after adding organic fibers, use.

Claims (11)

Claims Process for the continuous production of molded parts made of organic fibers, in particular ceramic fibers, asbestos fibers, stone fibers, Slag fibers, basalt fibers and / or glass wool, optionally mixed with organic fibers, using a vacuum, characterized in that one subjects the fibers to a thorough breakdown, preferably with buffer stirring, preferably having the fibers ionically neutral and at a practically neutral one adjusts pH, then charges with silica gel and then precipitates with anionic starch, the fiber liquor is continuously distributed homogeneously on a transport screen leaves and by vacuum to produce an endless further transportable fiber web drained from above without significant roller pressure and the running, green Fiber web. optionally further deformed and then fed to a dryer. 2. The method according to claim 1, characterized in that the Performs drainage by constant or increasing vacuum. 3. The method according to any one of claims 1 to 2, characterized in that that manie used fiber liquor by dissolving or opening up the fibers with a pulper or using air stirrers. 4. The method according to any one of claims 1 to 3, characterized in that that the vacuum is applied at a distance from the point of contact of the fiber liquor. 5. The method according to any one of claims 1 to 4, characterized in that that you can adjust the strength of the fiber web by appropriate setting the concentration of the fiber liquor flowing onto the transport wire is regulated. 6. The method according to any one of claims 1 to 5, characterized in that that the dewatering of the fiber web up to a dry content of 30 to 55% performs. 7. The method according to any one of claims 1 to 6, characterized in that that a gas-blowing agent and / or a binder is added to the fiber liquor. 8. The method according to claim 7, characterized in that the Binder in an amount of up to 6 wt. °, b, based on the fiber, is used, with in particular 40% silica sol is used. 9. The method according to claim 6, characterized in that the gastric agents in an amount of 0.1 to 1%, in particular in an amount of about 0.4%. 10. The method according to any one of claims 1 to 7, characterized in that that you roll on the top of the fiber web during dewatering with a low pressure can act. 11. The method according to any one of the preceding claims, characterized in that that one can deform the green. Fiber web, if necessary after parts of the same, carried out continuously by appropriate training of the support sieve.