CS252664B1 - Mixture for making ceramic and refractory products - Google Patents

Abstract

The mixture contains, as a temporary firming agent, from 2 to 6 wt. % of sulphite liquor, concentrated to 50 to 60 wt. % of dry matter.

Description

The present invention relates to a composition for the manufacture of ceramic and refractory products, in particular abrasive tools consisting of a filler, a binder and a temporary strengthening agent.

A number of different ceramic and refractory products, in particular abrasive tools, are manufactured by adding to the base material, a filler such as silica sand, fireclay, fired flake, sintered magnesite, corundum or silicon carbide, a binder component, binder. The binder used is usually of a ceramic nature, as it contains various frits and glass in addition to kaolin and clay, providing the products with the desired properties, structure, water absorption, hardness and strength after firing.

Therefore, a temporary binder must be used to ensure the unbonded handling strength. The temporary bonding agent used must not deteriorate the color of the product or degrade the base filler or cause other problems with the subsequent firing of the product. It must not have any physiological or biological harmful effects, nor must it have any odor in order not to impair the working environment.

Among the known substances currently used as temporary binders, various urea-formaldehyde resins, acrylate dispersions, water glass, paraffin emulsions, phenol-formaldehyde resins and others are known.

Dextrin in the form of a powder or a 30% solution, or both, is predominantly used in many manufacturing fields, particularly in the manufacture of abrasive tools. Test specimens, pressurized at 20 MPa, have an average flexural strength of 0.8 MPa after 20 hours of drying at 20 ° C and are considerably brittle.

The main drawback of this production method is that, besides the low strength, dextrin, which is a product of roasting starch derived from potatoes, is an important food product.

It is further known to use a powdered sulphite liquor from which a solution with the desired binding effects is prepared. Compared to dextrin, a bending strength of 1.0 MPa is achieved. The low flexural strength as well as the very difficult re-dissolution of the pulverulent sulphite liquor can be explained by the fact that during its production it undergoes thermal changes and degradations, thereby reducing its binding ability and solubility. The caramelization of pentosans and reaction of inorganic fractions with flue gases are very likely.

According to the invention, the aforementioned drawbacks are eliminated by a mixture for the manufacture of ceramic and refractory products, in particular abrasive tools consisting of a filler, a binder and a temporary strengthening agent consisting of sulphite leachates. It is based on the use of a sulphite liquor concentrated to 50 to 60% by weight. % solids in an amount of from 2 to 6 wt.

The advantage of the compositions according to the invention is, in particular, that a higher strength of the products is achieved immediately after formation and the strength increases by the progressive drying, which enables earlier and safer handling and storage of the semi-products. It is furthermore advantageous that the products can be dried at 25 ° C. The advantage of the concentrated leach is also its normal production in constant quality. It is the most economically advantageous of all known temporary binders used up to now. The biggest advantage is that it allows to fully replace dextrin, respectively. the starch from which dextrin is made, so that the starch can be used for food purposes and the like.

High bending strengths of up to 2.8 MPa with thickened sulphite liquor compared to 0.80 MPa of dextrin or 1.0 MPa sulphite liquor mixtures can be explained by the fact that thickening of a still aqueous sulphite liquor solution , it does not undergo thermal changes and degradation, nor does it caramelise pentosanes or react with inorganic fractions with the flue gas, thereby reducing its binding ability and solubility.

The composition according to the invention is described in more detail below on two exemplary embodiments.

Example 1

Ke 100 wt. % of a mixture consisting of 88 wt. % abrasive grain white corundum and 12 wt. % ceramic binder was added 4.0 wt. % temporary binder in the form of a sulphite liquor concentrated to 55 wt. % dry matter. The mixture was thoroughly kneaded and passed through a No. 16 sieve. The test pieces were pressed at 20 MPa and did not stick to the metal molds. After drying for 20 hours at 25 [deg.] C., the flexural strength was found to be 0.8 MPa with dextrin bodies and to 1.90 MPa with respect to Example 1, which is an increase in strength of 137.5%.

Example 2

Ke 100 wt. % of a mixture of 84 wt. % abrasive grain of green silicon carbide and 16 wt. % of ceramic binder was added 4.5 wt. % temporary binder in the form of a sulphite liquor, concentrated to 55 wt. % dry matter. The mixture was thoroughly kneaded and passed through a No. 12 sieve. The test pieces were pressed at 20 MPa and did not stick to the metal molds. After drying at 20 [deg.] C. for 20 hours, the flexural strength of the dextrin bodies was 0.51 MPa and the bodies according to Example 2 were already 1.58 MPa, which is an increase in bending strength of 210 [deg.].

Claims (1)

Mixture for the manufacture of ceramic and refractory products, in particular abrasive tools, consisting of a filler, a binder and a temporary strengthening agent consisting of sulphite liquors, characterized in that a sulphite liquor, concentrated to 50 to 60% by weight, is used. % solids in an amount of from 2 to 6 wt.