DK155658C - Process for preparing a hydrothermal curing, asbestos-free, refractory mold body - Google Patents

Description

1DK 155658 B

The invention relates to a process for the production of a hydrothermal-curing, asbestos-free, refractory building plate of calcareous and silica-containing components, cellulose fibers and, where appropriate, inorganic fibers. The moldings produced by the process are especially building boards.

U.S. Patent No. 1,239,608 discloses a process for preparing mold bodies in which perlite and vermiculite are agitated with cellulose fibers using a hydraulic or bituminous binder to produce a slurry which is dewatered and using pressure and, as appropriate. under the influence of heat is pressed into molds. The moldings made according to this method have only 15 bending strength and a very insufficient refractory.

DE Publication No. 2,411.864 discloses a method of producing fire-resistant sheet products in which short and long stack glass fibers, hydraulic cement, silica, cellulose fibers, where appropriate, perlite and / or diatomite and water are mixed into a slurry. The slurry is then formed into plates which are compressed, aged, treated in autoclave and dried. Although these plates have an improved flexural strength compared to the moldings produced in accordance with 25 DE patent specification 1,239,608, their fireproof is not satisfactory.

A method of the kind mentioned at the outset is known from DE Publication No. 1,646,962. The mold body 30 produced by this method has a large thermal shrinkage which leads to fracture of the mold body at high temperatures and thus to a low refractory.

The object of the present invention is to provide a method of the kind mentioned in the preamble to which building boards with high bending strength and fireproof can be manufactured.

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This object is fulfilled by the method of claim 1.

The method according to the invention is used for the production of building boards. However, it should be noted that the term "building board" is used in the broadest sense ie. as a term for boards which can be used for any desired construction purpose. Thus, for example, this term also includes plates used in ships and is known as ship plates.

The reinforcing cellulose fibers are, for example, fibers made from pulp for papermaking, for example, pulp made by the sulphate or sulphite process or by a mechanical process and pulp of all species from waste wood, jute, flax, cotton, straw, esparto grass, hemp, "rattle" and baggage. see.

In addition, the mixture can be added to inorganic fibrous reinforcing materials. Depending on the additional reinforcing materials and also the application to which the building boards of the invention are to be used, the reinforcing material may contain anything from 5 to 100% by weight cellulose fibers. However, although the cellulose fibers are mainly used for reinforcing purposes, they impart some of the fireproof to the building boards made according to the method of the invention. An improved refractory may be obtained by additional inorganic fibrous reinforcing materials used in conjunction with the cellulose fibers and comprising mineral fibers such as glass fibers (including alkali-resistant glass fibers), slag wool fibers and alumina fibers, ceramic fibers, alumina fibers, zirconium oxide fibers, and zirconia fibers. Any of these fibers or yarns or all of these fibers or yarns may be coated, for example, with alkali resistant materials. When these additional 3

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When fibrous reinforcing materials are used, they are preferably added in an amount of 95-0.5% by weight and preferably 40-10% by weight relative to the total weight of fibrous reinforcing materials.

The water-curing inorganic binder is an autoclave-treated or non-autoclave-treated combination of silica-containing components (i.e., a material containing reactive silica such as PFA (powdered fly ash), quartz sand, clay or diatomite) and calcareous components (i.e., any mineral, raw material) waste product containing more than 30% CaO, eg burnt lime). The mixture can also be added to cement.

The inorganic binder is preferably added in an amount of 70-90% by weight of the total weight of binder and fiber.

In the process of the invention, mica and / or vermiculite are added to the mixture in an amount up to 50% by weight relative to the total solids content of the mixture. A particularly important result of the use of vermiculite and / or mica in the inventive method is improved shrinkage properties of the resulting building board. A slight shrinkage at high temperatures is a characteristic which makes the sheets made according to the method of the invention particularly interesting for the construction industry.

Other fillers which may be contained in the blend used in the process include granulated, cellular or fibrous fillers such as perlite, silica, clay and clay waste, carbonate such as lime, dolomite and magnesium carbonate, wollastonite and other calcium silicate compounds. These may be present in an amount of 1-50% by weight relative to the total solids content. It should also be noted that silica, clay and clay wastes when they contain reactive silica can be a component of the binder.

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In the process of the invention, according to a variant, an aqueous slurry of the mixture can first be prepared. This aqueous slurry usually has a solids content of 3-20% by weight or more, for example 30% by weight. The slurry may be heated somewhat, for example to 25-45 ° C, and may contain small amounts of such additives as flocculants for controlling retention of starting material and as filtration aids (such as polyacrylamides), water retention aids, modifiers to the water content (e.g. carboxymethyl cellulose ethylene, wetting agents (e.g., detergents), and hardening agents (e.g., calcium chloride and lignosulfonates).

The slurry can then be molded into sheets by any method of manufacturing fiber reinforced cement building boards. These methods are, for example, (a) the Hatschek method, (b) the Magnani method, (c) the use of a single press, and (d) the Fourdrinier method, in which the plates are dewatered to a degree so that they are easy to handle. In the Magnani process, the slurry is applied to a continuous piece of felt between two driven distributor rollers. The distributor rollers are arranged on a trolley which is moved back and forth over a certain length of the device. Below the felt are a number of interconnected vacuum boxes and these are moved forward with the unbroken felt. While the water in the vacuum is removed from the slurry on the felt, the volume of the material is further increased during each passage of the distributor rollers which move back and forth. When the plates thus formed leave the area covered by the movement of the distributor rollers, they are further drained by the vacuum boxes. The plates then run through a set of oscillating caster rolls which smooth the surfaces of the plates and through which the plates get their final thickness. Pia- 5

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they are then completed and cut to the desired length.

After the sheets are made by any of these generally known methods, the binder and, where appropriate, the cement is given the opportunity to harden or bond. This is done by an autoclave treatment. The plates can then be dried immediately.

The starting slurry is usually prepared by grinding (water pulping) and dispersing the fibrous material to contain the pulp in water, followed by addition of the other powdery materials to form a slurry having an approximate water-solid ratio of 5: 1 to 10: 1. The slurry is then further diluted with water to provide a water / solid ratio of approx. 25: 1st Plates of this slurry are then prepared by dewatering on the machine used to provide a water / solids ratio of approx. 1: 1.

When intended to produce shaped articles other than building boards, the pulp is composed so as to obtain a viscosity suitable for the particular intended manufacture. Thus, in the manufacture of pipe lengths, the mass must be substantially more viscous than in the manufacture of sheets.

In another variant of the process according to the invention, the inorganic binder is formed just before it is mixed with the fibers. Thus, for example, burnt lime (the calcareous component) and quartz (the siliceous earth component) can be reacted or reacted prior to an autoclave with stirring to form tobermorite. The fibrous filler material mica and / or vermiculite and any other filler material is then stirred into the aqueous system of tobermorite which is then brought into the desired shape, optionally further autoclaved, drained and dried.

In a further embodiment, a slurry of the calcium silicate forming components, 6, is prepared

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reinforcing fiber material, mica and / or vermiculite and water and this slurry is added to freshly made tobermorite or xonotlite. The mixture is then formed, dewatered, autoclaved and dried. As previously described.

The invention will now be described in more detail by way of example, in which all of the stated proportions are by weight.

EXAMPLE 1

A mixture of 6 parts cellulose fibers and 6 parts alkali resistant glass fibers is dispersed in water, then 37.7 parts of burnt lime, 15.8 parts of quartz, 21.5 parts of diatomite and 13.0 parts of vermicult are added to produce a slurry with a water: solids ratio of approx. 10: 1. The slurry is formed into plates by dewatering on a Hatschek machine, thereby obtaining a water solids ratio of 1: 1. The shaped plates are treated in autoclave at 10.5 atm for 18 hours and the final product has a density of 710 kg / m3 and a breaking strength of 8.6 N / mm2.

Similar results are obtained when the plates are manufactured on a Magnani machine or in a press.

EXAMPLE 2

Using a similar method as in the aforementioned example, building boards were prepared on a press from an aqueous slurry containing 10 parts of cellulose fibers, 50 parts of vermiculite, 21 parts of burnt lime and 19 parts of quartz. The plates were treated in an autoclave for 36 hours at 10.5 at and they had a density of 600 kg / m 3 and a breaking strength of 6.5 N / mm 2. EXAMPLES 3 AND 4

Using the basic method described in Example 1, building boards of the ingredients listed in the following Table II were prepared using the conditions also set out for the autoclave treatment. The cellulose fibers were dispersed in water and ground (subjected to water pulping), the other 7

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Rich ingredients were added and the resulting slurry thoroughly mixed and further diluted. It was formed into plates using the methods indicated and the plates were autoclaved. The plates thus produced possessed the specified properties.

The indicated "MFT" crack test (micro fire test) was performed as follows: One block of each product with a diameter of approx. 100 mm and a thickness of approx. 10 mm was heated at the rate specified in British Standard BSS 476, Part 8 10 (1972). This rate is given in the following Table I, in which.T is the oven temperature in ° C at time t and T0 is the furnace exit temperature, which should be between 10 ° C and 40 ° C:

TABLE I

15 __

Time t Temperature increase min in oven (T - Tq) 20 25 10 15 30 60 90 120 180 240 360 556 659 718 821 925 986 1029 1090 1133 1193

The time taken from the onset of heating to the appearance of the first crack was noted in the last line of Table II below.

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TABLE II

Ingredients and Properties Example 3 Example 4 Cellulose (% by weight) 12.0 10.0 Lime (%) 31.8 • 42.0 Quartz (%) 29.2 21.0 Vermiculite (%) 12.0 12.0 Cement ( %) 15.0 15.0 Method of preparation Hatschek or Magnani Hatschek or Magnani Autoclaving conditions ca.9i ~ 10at / 24h ca.9i ~ 10at / 24h 3 Density (kg / m) 725 715 2 Fracture strength (N / mm) 12 5.5 MFT crack (minutes) EXAMPLE 5

Tobermorite-type aqueous calcium silicate was prepared by reacting ground quartz and hydrate lime at a molar ratio of Ca0: SiO2 of 0.9 to 1.0 in a stirred autoclave and under a vapor pressure of 9.44 atm.

16% by weight of stone wool fibers, 1% by weight of chopped fiberglass, 1% by weight cellulose pulp and 20% by weight of ground mica were added to the binder thus produced. The mixture was thoroughly stirred and then pressed into plates by a hydraulic press and a dewatering mold. The plates were dried at 150 ° C.

The properties of these boards were measured as were the properties of boards which were made in the same way but without any mica content. The results are shown in Table III below. As can be seen from the values for

Claims (3)

9GB 155658B shrinkage at high temperatures gives the mica-containing material a significant improvement, which in turn leads to improved TABLE III refractory. Properties Material Material without mica with Mica Density (kg / m ^) 270 285 Compressive strength (bar) 18.6 17.9 Flexural strength (bar) 4.68 4.13 Heat shrinkage (%) 950 ° C 2.95 1.30 1000 ° CO to "tf 2.20 PATE NTRRAV A process for preparing a hydrothermally curing, asbestos-free, refractory building board of 20 calcareous and siliceous components, cellulose fibers and, where appropriate, inorganic fibers, characterized in that the mixture is added to vermiculite and / or mica in an amount up to 50% by weight. the total solids content of the mixture, and that the calcareous and silicon-containing components are reacted in an autoclave before and / or after the mixing and molding. Process according to claim 1, characterized in that the mixture is added to cement. Process according to claim 1 or 2, characterized in that the inorganic binder is present in the mixture in an amount of 70-90% by weight of the total amount of binder and fiber.