DK155658B - - Google Patents

Description

DK 155658B

The invention relates to a process for the preparation of a hydrothermal-curing, asbestos-free, refractory mold body of calcareous and siliceous 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 process for the production of 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, in which molds with high flexural strength and fireproof can be manufactured.

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This object is fulfilled by the method of claim 1.

The process according to the invention can be used for the preparation of all kinds of mold bodies, for example plates, blocks and pipe lengths. It is particularly suitable for the manufacture of building boards and is referred to in the following description. However, it should be noted that the term "building board" is used in the broadest sense ie. as a term for slabs 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 cellulosic 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, "ramie" and bagasse .

In addition, the mixture can be added to inorganic fibrous reinforcing materials. Depending on the additional reinforcing materials and also on the use to which the moldings of the invention are to be used, the reinforcing material may contain anything from 5 to 100 weight percent cellulose fibers. However, although the cellulose fibers are mainly used for reinforcing purposes, they impart some of the fireproof to the moldings 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 these include mineral fibers such as glass fibers (including alkali-resistant glass fibers), slag wool fibers and rock wool fibers, ceramic fibers, alumina fibers, and zirconia fibers.

DK 155658 B

3 metal wires. 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 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 (ie, a material containing reactive silica, e.g. PFA (powdered fly ash), quartz sand, clay or diatomite) and calcareous components (i.e. any mineral). or 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 can be 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 formed body. 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 mixture used in the process include granulated, cellular or fibrous fillers such as perlite, silica, clay and clay wastes, carbonates such as lime, dolomite and magnesium carbonate, wollastonite and other calcium silicate fillers. These may be present in an amount of 1-50 wt.

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4 conducting solids content. It should also be noted that silica, clay and clay wastes when they contain reactive silica can constitute a component of the binder.

In the process according to the invention, an aqueous slurry of the mixture can first be prepared according to a variant. 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, ), wetting agents (e.g., detergents), and hardening agents (e.g., calcium chloride and lignosulfonates).

The slurry can then be formed into slabs by any method of making building slabs of 20 fiber reinforced cement. These methods are, for example, (a) the Hatschek method, (b) the Magnani method, (c) the use of a simple press, and (d) the Pourdrinier method, in which all the plates are dewatered to a degree so that they are light. 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 35 thus formed leave the area covered by the movement of the distributor rollers, they are further drained by the vacuum boxes.

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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. The plates are then finished 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 be contained in the pulp, followed by the addition of the other powdered materials to form a slurry having an approximate water to 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 it is intended to produce shaped articles other than building boards, the pulp is composed so as to obtain a viscosity suitable for the particular intended preparation. 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 of 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) may be reacted or reacted prior to an autoclave with stirring to form tobermorite. The fibrous filler material glitters 35 and / or vermiculite and any other filler material is then stirred into the aqueous system of tobermorite which

DK 155658B

then brought into the desired shape, optionally autoclaved, drained and dried.

In a further embodiment, a slurry of the calcium silicate forming components, reinforcing fiber material, mica and / or vermiculite and water is prepared and this slurry is added to freshly prepared 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 fiber and 6 parts 15 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: 1: 1 solids ratio. 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 30 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 procedure described in Example 1, building panels of the

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7 the components listed in the following Table II using the conditions also set out for the autoclave treatment. The cellulose fibers were dispersed in water and ground (subjected to pulping), the other ingredients 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 having 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 (1972). This rate is given in the following Table I, in which T is the oven temperature in ° C at time t and TQ is the oven output temperature, which must be between 10 ° C and 40 ° C:

TABLE I

20 __________

Time t Temperature increase min in oven (T - TQ)

° C

25 5 556 10 659 15 718 30 821 60 925 30 90 986 120 1029 180 1090 240 1133 360 1193 35 The time taken from the beginning of heating to the appearance of the first crack was recorded in the last line of Table II below.

TABLE II

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Ingredients and properties Example 3 Example 4

Cellulose (weight percent) 12.0 10.0 5 -

Burnt lime (%) 31.8 42.0

Quartz (Z) 29.2 21.0

Vermiculite (Z) 12.0 12.0

Cement (Z) 15.0 15.0 _ .... ^ j Hatschek or Hatschek or

Fremstillingsmetode__jfagnani__Mamani

Autoclaving conditions ca ^ i3 ^ / 24h ca.9i atjn / 24h - --— 3-, .. - --------

Density (kg / m) 725 715 ^ 5 Breaking strength (N / mm ^) 12 5.5 MFT crack (minutes) 15 20 20 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 an autoclave with stirring 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 plates were measured as were the properties of plates prepared in the same manner but without any gum contents. The results are shown in Table III below. As can be seen from the values for

Claims (3)

5 TABLE III Properties Material Material - without mica with mica Density (kg / m 2) 270 285 10 Compressive strength (bar) 18.6 17.9 Bending strength (bar) 4.68 4.13 Heat shrinkage (%) 950 ° C 2.95 1.30 1000 ° C 4.50 2.20 15 A process for preparing a hydro-thermosetting, asbestos-free, refractory mold body of calcareous and siliceous components, cellulose fibers and, where appropriate, inorganic fibers, known by the addition of the mixture to vermiculite and / or mica, and the calcareous ones. and the silicon-containing components are reacted in an autoclave before and / or after 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 30% by weight of the total amount of binder and fiber. 35