SU825263A1 - Cold hardenable mixture for producing casting moulds and cores - Google Patents

Description

The invention relates to foundry, in particular, to the composition of mixtures for the manufacture of cores and molds that are curable in cold rigging. The cold-hardening mixture (who), containing a refractory base, phenolic resin, aromatic sulfonic acid, aminosilane and the addition of semi-aquatic gypsum 113, is known in the XTC as a binder, and phenol cmrla is relatively expensive and highly toxic. XTC is also known, which contains a refractory filler, an acid catalyst, an alkyl aryl sulfonate and a lower amount of urea CMOjjB .. (0.5-2.5 wt.%). Due to the low resin content, such XTC has improved sanitary and hygienic properties, however, its scope is limited due to the lower heat resistance. Closest to the proposed technical essence and the achieved result is TCS, containing a refractory filler, a urea resin, a sulfite yeast mash and an acid hardener C3j. This mixture has a higher heat resistance than mentioned earlier, due to the presence of a sulfite yeast brew in its composition, and for the same reason it is not sensitive to fluctuations in the clay content of the filler. However, the mixture is characterized by an increased resin content, which leads to significant toxic gases, especially when casting and embossing the forms, i.e. the mixture has a low in comparison with the best samples of XTC sanitary and hygienic characteristics. The latter can be improved by selecting the resin content at the lower limit. (1.5 wt.%, But at the same time, the thermomechanical properties of rods and molds from HTS are impaired. The purpose of the invention is to improve the sanitary-hygienic characteristics of the mixture while maintaining its thermomechanical properties. The goal is achieved by the fact that the cold-hardening mixture for the manufacture of casting cores and molds, includes refractory filler, urea resin, sulphite yeast mash and acid hardener, additionally contains calcium sulphate hemihydrate at the following ratio of ingredients,

weight.%:

Refractory filler 100 Carbaglide resin 0.8-2.0 Sulfite yeast b; razka 1.0-3.5 Acid hardener, calculated on the dry matter 0.2-0.5 Calcium sulfate hemihydrate 1.0-3.0

As an acid hardener, the mixture contains an aromatic sulfonic acid, preferably benzenesulfonic acid crystalline hydrate.

. An example of a product based on potkha calcium sulfate hydrate is hemihydrate gypsum.

When the content of calcium sulfate hemihydrate is below the lower and above the upper limits of its positive effect on the stabilization of the thermomechanical properties of the HTS with a lower content of urea resin in the mixture is not observed.

The proposed HTS is prepared as follows.

. First get a complex hardener. For this, crystalline hydrated benolesulfonic acid (as an initial solid, is dissolved in a sulphite-yeast mash (RBD), using a

the ratio of ingredients Sleep 1,03, 5 weight.h. SBD - 0.2-0.5 weight.h. the original solid benzene sulfonic acid}.

The addition of gypsum is introduced into dry sand and stirred for 1 minute, then resin is added and mixed for another 1 minute, after which the complex hardener is introduced and after 0.5–1 minutes of mixing, the HTS becomes ready for use.

In tab. 1 shows the composition of the proposed CTS and known in table. 2 - properties of these mixtures.

Compositions 1-3 and 5 illustrate the physico-mechanical parameters of the proposed CTS in the curing process, compounds 4-6 - thermomechanical properties. From a comparison with similar properties of the known Cs} XTS (compare mixtures 4c7, 5c8 and 6c9 / it follows that the heat resistance of both CTS is about the same, but in the proposed one it was achieved with a carbamide resin content of 1.5 parts by weight (respectively 0.038% of free formaldehyde in CTS) whereas in the known one it was achieved with a higher content of urea smrlts - 2.5 parts by weight (respectively 0.0625% of free formaldehyde in the HTS). It follows that the proposed HTS has improved sanitary and hygienic properties.

Thus, the proposed mixture provides improved sanitary and hygienic working conditions without compromising the thermomechanical characteristics of the rods and shapes.

Table

Quartz sand K016A 100 100 100 100 Urea resin (UCS) 0.8 0.8 2.0 1.5 Sul Fitnozhrozhva 1.0 3.5 3.5 1.0 beer Benzene sulfonic acid (initial solid) 0.2 0.5 0.5 0.2 Building gypsum. . (semi-aquatic) 1.0 3.0 3.0 1.0 100 100 100 100 100 1.5 1.5 2.5 2.5 2.5 2.5 2.0 3.5 1.0 1.0 2.0 4.0 0.5 0.5 0.2 0.4 0.6 2.0 3.0

table 2

Claims (3)

Claim 1. Cold-hardening mixture for the manufacture of foundry cores and molds, including a refractory filler, urea resin, sulphite-yeast mash and acid hardener, characterized in that, in order to improve sanitary and hygienic properties, it additionally contains calcium sulfate hemihydrate 50 ounce in the following ratio of ingredients, parts by weight ·. Fireproof weight gain 100 55 Carbamide resin 0.8-2.0 Sulphite-jitter chewy mash 1.0-3.5 Acid hardener in terms of dry weight 60 society 0.2-0.5 Calcium sulfate hemihydrate 1.0-3.0 • 2. The cold hardening mixture according to claim 1, which is characterized in that it contains aromatic sulfonic acid as an acid hardener. • 3. Cold hardening mixture according to paragraphs. 1 and 2, characterized in that as aromatic sulfonic acid it contains <crystalline benzol sulfonic acid’s hydrate’’ ......