FI71334B - SKYDDANDE BELAEGGNINGSSKIKT - Google Patents

Description

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Protective coating

The present invention relates to a protective coating layer to prevent dust and / or water-induced extraction and / or the spread of fire.

The object of the present invention is to make it possible to prevent dusting, casting with water or the spread of fire by coating products or objects per se with a protective layer which can be easily removed mechanically.

Industry is often forced to use outdoor storage for dusty products, making the environment easily polluted in windy weather. In addition, both dusty and non-dusty products are stored outdoors in places where snow and rain can damage the products or cause the extraction of toxic substances or substances intended to give the products a certain characteristic. For example, large quantities of gravel and sand are stored outdoors to prevent slipping during the winter. Salt has been mixed with this gravel to prevent the heaps from coalescing, making the gravel / sand inaccessible. However, during varying periods of rain and shelter weather, water passes through the heaps, causing the water to extract salt, so that the frost protection is removed and the heaps freeze together.

Other examples are carbon stocks, which often dust and smoke down into the environment, especially in coal mines.

In certain cases, it is desirable to provide the products with a non-permanent fire protection layer, for example in connection with welding work carried out near flammable material.

Previously, protective layers of carbon stocks have been proposed (U.S. Patent 4,269,721) in which a gypsum layer is formed on top of the store.

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However, the disadvantage of gypsum is that it is water-soluble, which is why the protective layer dissolves as it is poured, for example, by water in the form of rain.

Other protective layers of sodium chloride, clay and water are also known (U.S. Pat. No. 3,896,039), which, however, have the same disadvantages as gypsum because they are water-soluble and thus do not provide protection in external storage.

In addition, the product does not solidify quickly enough, which is another requirement for outdoor storage.

Still other anti-dust layers are known (GB patents 1,245,165, 1,267,621 and 1,267,617), in which case hygroscopic salt and e.g. gypsum are mixed with water and applied to the products which it is desired to prevent dusting. These layers are also water soluble.

GB patent 1,391,115 discloses a method for preventing dusting in rock extraction, in which the rock is cast with an aqueous solution of a polysaccharide such as guar gum, sodium carboxymethylcellulose. This solution may provide temporary protection against dusting but not permanent protection.

SE application 7603820-7 discloses a flame retardant protective layer consisting of an inorganic component comprising an alkali metal silicate, an aqueous solution of clay and asbestos fibers, and an organic component comprising carboxylmethylcellulose, a starch ester and / or an aqueous solution of dextrin, the organic component being other percent of the total. However, such a mixture has e.g. too long curing time,> 48 hours.

The requirements for the protective layers used for external protection include that it must be effectively protected from moisture, preferably within a few hours and at the latest within 24 hours, that it must not dissolve within a reasonable time, which means 6-8 months, that it must be 3 71334 environmentally friendly and the coated product must be damaged and must be easily removable so that the stored products are easily accessible. In addition, when storing cheap products, protection must not be too expensive.

It has now surprisingly proved possible to meet the requirements of the present invention, which is characterized in that it contains, in addition to gypsum, cement and ethylhydroxyethylcellulose, the weight ratio of gypsum: cement does not exceed 6: 1, and the amount of water required to solidify gypsum and cement. the amount is 0.2-3% by weight of the water used.

Other features of the invention will become apparent from the appended claims.

Example 1

An aqueous (r) solution of 1% ethylhydroxyethylcellulose (Bermocell® E 481, Berol Kemi, Stenungssund, Sweden) was prepared.

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The mixing vessel, which held 7 m, was then charged with a total of 5 m consisting of 44 parts of CaSO 4 * 2H 2 O, 22 parts of cement and 34 parts of said 1% aqueous ethylhydroxyethylcellulose solution. The total weight was 6.7 tons. The mixture was homogeneous by stirring with a melasixer for 1 hour.

This slurry, which had a viscosity of about 1000 cPs, was sprayed onto a sand reservoir containing about 1200 sand, first pouring the peak and then the sides. The applied layer dried quickly and was hard after about 11 hours. The average thickness of the protective layer was about 5 mm. The protective layer was completely stable after 20 hours, practically insoluble in water and had a water permeability after solidification of 1.10 μm / second.

Examples A-D

For comparative purposes, various coating layers containing other components were prepared as described below.

_ _ ττ ~ _ 71334 4 A. 200 g H 2 O 200 g CaSO 4 · 2H 2 O 100 g cement 5 g carboxymethylcellulose B. 240 g K 2 O 60 g CaSO. · 211 „0 r 4 2 20 g cement 20 g bentonite C. 40 g α-hemicellulose 20 g bentonite 140 g CaSO 4 · 2H 2 O 200 g K 2 O D. 175 g H 2 O 200 g CaSO 4 · 2H 2 O 100 g cement 3 g carboxymethylcellulose A and D mixtures gave stable protective layers only after more than 2 days. The mixtures of B and C solidified within a reasonable time of 10-24 hours, but were both water soluble.

In the preparation of the mixtures according to the present invention, only the amount of water which is bound by the layer on solidification, i.e. which is mainly absorbed by the cement, is suitably added. Suitable viscosities during manufacture, transport and application are 500-1500 cPs.

The amount of ethylhydroxyethylcellulose used as a binder may be 0.2-3% in aqueous solution. When larger amounts are used, the aqueous solution cannot be treated due to swelling of the cellulose derivative. The amount of cellulose in the product can, of course, be high, but in that case it also tilts it considerably. The weight ratios between gypsum and cement should be about 3: 1, but never more than 6: 1, because the solubility then becomes too high and the physical strength decreases. Due to the cost, the amount of 5 71 334 gypsum is suitably not less than the amount of cement.

The gypsum used must not be too large, but must have a principal particle size of less than 0.25 mm and all particles less than 1 mm.

The gypsum mentioned in the examples has been dihydrate gypsum,

CaSO 2 · 2H 2 O, but also anhydrite gypsum or hemihydrate gypsum can be used. With the latter grades, stronger solidification and bonding occurs when the gypsum changes to the dihydrate form. When using anhydrite gypsum and semi-hydrate gypsum, the amount of water in the mixing step must be slightly increased. However, the total amount in the final floor is the same.

Up to 2% by weight of CaCl 2 can be added to the protective layer product to accelerate curing.

Depending on the type of storage and product, the storage location and a few other conditions, the thickness of the protective layer may vary between 1-10 mm, preferably about 2-5 mm.

When manufacturing takes place on site at the warehouse, it can be difficult to determine the appropriate viscosity for the product. Therefore, it has proved suitable to perform a funnel test, i.e., to fill the funnel with solution and to measure the time of fast or slow emptying of the funnel. The viscosity of a product having a composition of 225 g CaSO 2 · 21 ^ 0.75 g cement, 1.5 g ethyl ethylhydroxyethylcellulose and 180 g water is considered suitable.

This product flows through a funnel with a height of 80 mm, an upper diameter of 120 and a lower diameter of 14 mm in 50 seconds. If the amount of water is 170 g, the time is 90 seconds, and if the amount of water is 190 g, the time is 35 seconds.

Claims (4)

1. The composition of the gypsum plaster, which comprises a mixture of gypsum and ethylhydroxyethylcellulose gypsum, a coloring agent of plaster: cement in an inverter of 6: 1, the same water content of the cast iron formulation, 2-3% by weight of water. A protective coating layer containing gypsum, characterized in that it contains, in addition to gypsum, cement and ethylhydroxyethylcellulose, the weight ratio gypsum: cement not exceeding 6: 1, and the amount of water required for solidification of gypsum and cement, the amount of ethylhydroxyethylcellulose being 0.2 -3% by weight of water used. 2. The method of application of claim 1 is to provide a plaster: cement is 3: 1. Protective coating layer according to Claim 1, characterized in that the weight ratio of gypsum: cement is 3: 1. 3. The use of caffeine in the manufacture of caffeine, which may involve the use of CaCl 2. 2 Protective coating layer according to one or more of the preceding claims, characterized in that it additionally contains CaCl 2. 2 Protective coating layer according to one or more of the preceding claims, characterized in that it is applied with a layer thickness of 1 to 10 mm, preferably 2 to 5 mm. 4. The shielding cap is preferably set aside from the main patent, the sheaves being shown with a spacing of 1-10 mm, with a pitch of 2-5 mm.