CS250368B1 - Lightweight fiber insulation elements and manufacturing method - Google Patents

Abstract

The solution relates to lightweight fibrous products based on inorganic fibers and binders, designed for high working temperatures. The purpose of the invention is to increase the binding ability of the binder used and to increase both the handling and assembly strength of the finished products, as well as their heat resistance. This purpose is achieved in elements consisting of 50 to 92% by weight of inorganic fibers, 5 to 25% by weight of finely dispersed additives, formed by a mixture of kaolin and fly ash from the production of crystalline silicon, 1 to 15% by weight of colloidal silicon dioxide, 1 to 10% by weight of organic binder and 0.01 to 0.5% by weight of organic flocculent, preferably polyacrylamide. The production of these elements proceeds as follows: first, an aqueous suspension of inorganic fibers, finely dispersed additives, organic binder and flocculant is prepared, the suspension is partially drained on a screen dewatering machine, the wet carpet formed is immediately treated with at least one coating of colloidal silicon dioxide solution, the excess liquid is sucked off the carpet and, if necessary, used for re-coating, and the carpet is dried and cut into the required formats after passing between pressure rollers.

Description

The present invention relates to lightweight fibrous insulating elements based on inorganic fibers and binders intended for high working temperatures and to a process for their preparation.

Inorganic fibers in the form of free wool; felt, mats, boards, etc., are used for a variety of insulation purposes. Their non-flammability and good heat resistance create good conditions for applications at elevated temperatures. Namely, aluminosilicate fibers prepared by pulping fused silica-alumina mixtures or aluminosilicate melts allow deployment at operating temperatures of about 1200 ° C and above. Products made of these fibers are used for lining the interior of various types of furnaces and thermal aggregates, such as progressive insulation in metallurgy and foundry, etc. Additives of suitable binders are used for the preparation of the products mentioned above. The type of binder is chosen depending on the required properties of the element in terms of handling and behavior in operating conditions under the influence of vibrations, gas flow, etc., further with regard to technological requirements, economics etc. Where products from inorganic, especially aluminosilicate fibers increased heat resistance, inorganic heat-resistant binders should be used. Colloidal solutions of some oxides, such as SiO2, Al2O3, and the like, have proved to be particularly suitable for this purpose. Usually applied silicon dioxide is used in the form of aqueous salts having a particle size of approximately 10 to 100 μΐη, stabilized in an alkaline or acidic region. Inorganic binder products are prepared from aqueous suspensions of fibers and binders by dewatering in sieve forms or by papermaking on an endless sieve. A disadvantage of forming the inorganic fiber elements and the aforementioned inorganic binders, in particular a colloidal silica solution, according to the latter method, is that, without complete recirculation, large binder losses occur in the underwater waters; moreover, colloidal silica tends to migrate to the surface layers when drying the wet fiber mat, causing inhomogeneous bonding of the products. It has therefore been proposed to use a pre-gelation of the SiO 2 sol by the action of solutions of some salts, such as aluminum sulfate, to improve the entrapment of the binder in dewatering the suspension and suppressing migration. However, binder gelation results in a substantial reduction in its binder power and, moreover, worsens filtration and limits the amount of sol that can be introduced into the component suspension. In order to increase the inorganic binder content in the manufacturing and thereby improve their mechanical heat properties, it has been proposed to introduce sol S102 sol by sieve only into the molded wet fiber carpet containing a gelling additive and finely dispersed material added to further improve the binder trapping level. Despite the fact that it is possible to introduce more colloidal silica into the article, the problem of its reduced bonding ability due to gelation and hence the low handling strength of the resulting elements remains.

The aforementioned drawbacks are eliminated with the lightweight fiber insulating elements according to the invention which comprise 50 to 92% by weight of inorganic fibers, 5 to 25% by weight of finely dispersed additives consisting of a mixture of kaolin and flakes from the production of crystalline silicon, 1 to 15% by weight of colloidal silica, 1 to 10% by weight of organic binder and 0.01 to 1.0% by weight of organic flocculants, preferably polyacrylamide.

In the production of the lightweight fiber insulating elements according to the invention, it is best to first prepare an aqueous suspension of inorganic fibers, finely dispersing additives, organic fibers, finely dispersing additives, organic binder and flocculant, the slurry partially drained on a sieve dewatering machine. the carpet is immediately treated with at least one coating of the colloidal silica solution, the excess liquid is sucked out of the carpet, and optionally used for re-coating, and the carpet is dried and cut to the necessary formats after passing between the pressure rollers.

The presence of an organic binder introduced into the fibrous carpet ensures high handling and assembly strengths of the resulting boards. The incorporation of S1O2 sol into the fiber carpet by frosting limits its overall consumption and allows at the same time to achieve a relatively high colloidal silica content in the product and hence high heat resistance. Due to the presence of the mixed dispersion additive, the addition of inorganic salts, namely aluminum sulphate, as the gelling agent for the S1O2 sol, can be reduced or eliminated as a further component. It has been found that the presence of a finely dispersed mixture of kaolin and fumed silica falling off in the production of crystalline silicon, together with an organic polyacrylamide-based flocculant, in the wet fiber carpet, also ensures a reduced tendency to migrate on drying product. Thus, it is possible by the method of the invention to introduce larger amounts of inorganic binder into the article, to suppress the inhomogeneous bonding of the article, to reduce the losses of S1O2 sol in the underwater waters and to provide good mechanical properties in handling and heat.

It is expedient to use a mixture of kaolin and S1O2 in a ratio of approximately 1: 1 as a dispersant. Furthermore, it is expedient for binder to be uniformly distributed by colloidal silica immediately after the main fraction of ka2 5 O 3 Ε 8 , allow suction rollers to pass through the squeezing rollers before starting suction. The liquid from the suction device downstream of the irrigation node, which may contain a portion of the excess colloidal SiO2, may optionally be recirculated and, after treatment, reused for icing.

Among the organic binders, it is possible to use preferably starch, lubricated starch or derivatives thereof, or some synthetic polymers in the form of aqueous dispersions. A good drainage and carpet forming process on the screen promotes the presence of an organic flocculant in the initial suspension of the components.

By using the composition and method for producing the lightweight fiber insulating elements of the present invention, an evenly bonded, sufficiently strong and manageable product is obtained which, due to the presence of a higher proportion of inorganic binder, retains good physico-mechanical properties even at higher temperatures. In the case of the use of aluminosilicate fibers, rigid plates are thus obtained, suitable, for example, for the lining of the furnaces of industrial furnaces with a high flue gas flow rate, etc. It is also possible to use a mixture of aluminosilicate and mineral fibers; In this case, a product having a higher temperature resistance than mineral wool itself can be used for insulation at operating temperatures up to 1000 ° C, preferably for the back insulation layers of industrial furnace linings.

The invention will be further elucidated by means of practical examples thereof.

Example 1

In a 30 L laboratory mixer, 330 g of aluminosilicate fibers, 30 g of kaolin, 30 g of SiCl 2, 8 g of starch in the form of 5% wax, 0.4 g of polyacrylamide-based organic flocculant in the form of 0.5 % solution and suspension was brought to a volume of 20 L by filtration molding in an aspirator

Claims (3)

SUBJECT 1. Lightweight fiber insulating elements prepared by drying a dewatered wet carpet of inorganic fibers, binders and additives, characterized in that it consists of 50 to 92% by weight of inorganic fibers, 5 to 25% by weight of finely dispersed additives consisting of a mixture of kaolin and ground crystalline silicon, 1 to 15 wt.% colloidal silica, 1 to 10 wt.% organic binder, and 0.01 to 0.5 wt.% organic flocculant, preferably polyacrylamide. Light fiber insulating elements according to claim 1, characterized in that it contains up to 3% by weight of an inorganic gelling agent, preferably aluminum sulphate. 3. Lightweight 30 X 30 cm borosized fiber insulated, perforated bottom, fitted with a fine sieve, a wet carpet was prepared which was poured over a 10 percent 1 liter colloidal silica solution, leveled several times with gentle pressure and the excess liquid retained was aspirated with using a vacuum under the sieve. After drying at 110 ° C, the resulting board exhibited uniform bonding throughout the thickness. The bulk density of the plate was 195 kg. m ~ ³ , flexural strength 0.45 MPa, after 2 hours annealing at 1000 ° C 0.25 MPa. Example 2 400 g of aluminosilicate fibers, 60 g of kaolin, 60 g of SiO2 20 g starch and 50 ml of a 0.5% polyacrylamide solution were mixed in 20 l of water. After draining the obtained suspension of components, the wet carpet was poured over with 300 ml of 20% S1O2 sol and after repeated pressure and suction of excess liquid was steamed and dried at 105 ° C. The uniformly bonded board obtained had a bulk density of 238 kg. m- ³ , flexural strength of 0.9 MPa, after 2 hours, annealing at 1000 ° C 0.5 MPa. Example 3 200 g of aluminosilicate fibers, 200 g of type B mineral wool, 50 g of kaolin, 50 g of SiO2 drift, 20 ml of a 50% aqueous dispersion of styrene-butyl acrylate polymer, 100 ml of a 10% aluminum sulphate solution and 20 ml were mixed in 20 l of water. 0.5% polyacrylamide solution. After draining the suspension obtained, the wet carpet was poured over 900 ml of 15% S1O2 sol and after repeated pressure the excess carpet liquid was aspirated. The obtained wet plate was dried at 105 degrees Celsius. The resulting uniformly interconnected plate exhibited a density of 217 kg. m ³ , flexural strength 0.55 MPa, after 2 hours annealing at 1000 ° C 0.35 MPa.