JPH0680150B2 - Coating composition for refractory coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applied to a graphite-based refractory, particularly a nozzle for continuous casting,
It is used in the steel and steel industry by forming a coating film.

(Prior art) Conventionally, immersion nozzle, long nozzle,
For refractory materials such as long stoppers, the mainstream of the material has shifted from silica graphite to alumina graphite, which has high corrosion resistance, but it is still present. Embrittlement is inevitable.

Further, there is an increasing demand for improvement in productivity and long life of the continuous casting method, and accordingly, stable physical properties of refractory materials are desired. Therefore, at present, these graphite refractories are currently coated with a coating material for forming an antioxidation layer in advance to prevent embrittlement due to oxidation. For this purpose,
Due to the severe operating conditions of graphite-based refractories, alkali silicates (potash glass, water glass, etc.) have been mainly used as the binder, and paints containing various types of frits and fillers have been applied.

(Problems to be solved by the invention) When a conventional coating material containing alkali silicate as a main binder is used, it is necessary to provide heat for a long time in consideration of spalling for drying after coating, and refractory materials. There was a problem that the carbon dioxide gas in the air and the coating film reacted with each other before being used, and the coating film was cracked or peeled off. Further, since the graphite-based refractory has a strong lipophilicity, there is a problem in the penetration and adhesion of the water-based paint. Further, since the binder itself does not have water resistance, there is a problem that the binder dissolves and flows out when stored in a place with high humidity for a long time. When a refractory product having a defect in these coating films is used, oxidative embrittlement of the refractory product progresses from the defective portion of the graphite-based refractory product, which may seriously hinder operation.

on the other hand. From the usage conditions, in recent years, with the improvement in productivity and the spall resistance of the graphite-based refractory itself, it is possible to use refractory without preheating or to give sufficient preheating time to make the coating ceramic. The number of cases in which the layer is used after it has been reduced, and there is also a demand for forming the antioxidant layer without preheating.

An object of the present invention is to form a coating film having excellent adhesion and weather resistance on a graphite-based refractory material, and to obtain a coating material exhibiting coating film physical properties having heat resistance and oxidation resistance in a wide temperature range. is there.

(Means for Solving Problems) In the present invention, the solution is to have an alcohol-dispersed silica sol, a synthetic resin, a glass frit and orthoclase as essential components in the coating composition.

Each of the constituents of the present invention will be described below.Silica sol is also referred to as colloidal silica, which is a colloidal solution in which ultrafine particles of high-molecular-weight silicic acid anhydride are dispersed in a solvent, a water-dispersible type, alcohol. There is a dispersion type, but in the present invention, it refers to an alcohol dispersion type silica sol.

In the present invention, the synthetic resin refers to a synthetic resin miscible with the alcohol-dispersed silica sol, and is generally a synthetic resin used as a coating film forming element under the name of synthetic resin paint. Examples of synthetic resins include acrylic resins, amino alkyd resins, alkyd resins, urethane resins, epoxy resins, vinyl chloride resins, silicone resins, urea resins, phenol resins, phthalic acid resins, unsaturated polyester resins,
Examples include melamine resins and cellulose derivatives. When the resin type is classified into a solvent type, a water-soluble type, and a water-dispersed type, solvent-type and water-soluble resins can be usually used.

The glass frit is an amorphous low-melting glass crushed product generally used for producing enamels, and a commercially available product may be used.

Orthoclase is a rock-forming silicate mineral and is a potassium feldspar containing KAlSi ₃ O ₈ as a main component, and may be any one used in the pottery industry.

In addition, thickeners, dispersants, wetting agents, defoaming agents, leveling agents, mildew-proofing agents, pigments and the like which are commonly used in paints are used as additives.

Then, in order to actually prepare the coating composition of the present invention, the compounding amount as shown below is used. However, the synthetic resin with silica sol is in solid content conversion.

Silica sol 1 to 5 parts by weight Synthetic resin 1 to 10 parts by weight Glass frit 10 to 100 parts by weight Orthoclase 50 to 100 parts by weight Additives Appropriate solvent to disperse Appropriate As a function of each component, silica sol is bonded. It functions as one of the agents and has better water resistance than conventional alkali silicates, and it melts into glass with other fillers when used.

The synthetic resin acts as another binder and has a role of imparting water resistance and moisture resistance to the coating film before use and improving the spall resistance of the refractory.

Glass frit and orthoclase are merely fillers when the coating film is dried, but when used, glass frit and orthoclase co-melt together to form a dense glass phase, together with SiO ₂ which is an essential component of silica sol. Prevent refractory oxidation.

(Function) The coating composition of the present invention is applied to a refractory at room temperature and dried,
Wait for the next action depending on each component when using.

Synthetic resin and silica sol have water and moisture resistance as a coating film from room temperature to 400 ° C, and silica sol acts as a coating film binder from 400 ° C to glass frit melt (700 ° C to 800 ° C) have. And from 800 ℃ to 160
Up to about 0 ℃, glass frit, silica sol, and orthoclase melt sequentially and have an antioxidant effect.

(Example) Hereinafter, the effect of implementation will be described with reference to Examples 1-2 and Comparative Examples 1-6 shown below.

The formulations of Examples 1-2 and Comparative Examples 1-4 are shown in Table 1 below. In the table, the components are alcohol-dispersed silica sol having a solid content of 30%, synthetic resin composition is vinyl acetate / acrylic resin in Example 1, and phenol resin composition in Example 2 and Comparative Examples 1 to 4, The glass frit with a melting temperature of 750 ℃ ~ 800 ℃, orthofeldspar is a raw material for the ceramic industry, which is commercially available. Is the amount of xylene used for dispersion. Numerical values are expressed in parts by weight.

Further, Table 2 shows the formulations of Comparative Examples 5 to 6 in which the conventional coating material for coating is alkali silicate as a binder. The numerical value indicating the blending amount is parts by weight.

The coating compositions of Examples and Comparative Examples having the above composition are applied to a graphite refractory (immersion nozzle) after the refractory is sufficiently dried. The coating composition was applied using a brush, and the application amount was about 1 Kg / m ² (wet state). Drying after coating was carried out at 80 ° C. for 1 hour in Example 1, and at 150 ° C. for 2 hours in Example 2 and Comparative Examples 1 to 4.
The thus-processed product was used as a test body for the firing test.

In the firing test, using a gas furnace (LP gas), the test body was heated from room temperature to 1000 ° C in about 10 minutes in an oxidizing atmosphere, and then heated to 1300 ° C in about 20 minutes to perform a firing test. In the firing test, the surface condition after firing was visually confirmed.

To check the water resistance, use a thin slice of graphite-based refractory (5
X 10 x 1 cm) with the entire coating composition applied and dried, then
IS K5663 Synthetic resin emulsion paint A water resistance test and an alkali resistance test stipulated in Type 1 were performed. For moisture resistance, the same as above, hang the test piece in a glass bottle with a thread, put water in the bottle to the extent that it does not touch the test piece, and put it in an atmosphere at 50 ° C for 1
Leave for months. Observe the change in the coating film in this state (100% humidity).

The above test results are shown in Table 3 below.

As can be understood from the results in Table 3, the coating composition of the present invention does not cause any abnormality even if it is baked without preheating. Further, since there is no problem in water resistance, alkali resistance and moisture resistance, the coating film does not have any defects before being used.

Furthermore, when an example is illustrated, in Example 3, in place of the vinyl acetate / acrylic resin of Example 1, a urethane resin (solid content
40%) and a curing agent with an external ratio of 20% relative to the weight of the urethane resin was used together. In Example 4, a water-soluble epoxy resin (solid content 50%) and a water-soluble melamine resin (solid content 77%), which were similarly synthetic resins, were mixed at a solid content ratio of 9: 1.

The coating and drying of the refractory material was carried out at 80 ° C. for 1 hour in Example 3, and at 150 ° C. for 30 minutes in Example 4. After that, various tests were performed in the same manner as in Example 1. The results are shown in Table 4.

From the results of Examples 3 and 4, even when the kind of synthetic resin is changed, the physical properties of the paint when used in the conventional paint are water resistance, alkali resistance,
It is understood that any composition having no problem in moisture resistance can be used in the coating composition of the present invention.

(Effects of the Invention) According to the coating composition of the present invention, since it is not water-based, it has excellent penetrability into refractories, the drying time can be shortened, and water that causes spalling does not remain. Moreover, due to its excellent water resistance, alkali resistance, and moisture resistance, coating film defects do not occur during storage, and even if the coated refractory is used without preheating, pinholes, sagging, cissing, etc. will not occur. No, no sport.

Therefore, it has become possible to provide a graphite-based refractory material with high productivity, which does not cause a problem of long or short storage period.

Claims (1)

[Claims] 1. A coating composition for refractory coating, which comprises, as essential components, an alcohol-dispersed silica sol and a synthetic resin that is not water-dispersed as a binder, and glass frit and orthoclase as fillers.