SU68593A1 - Method of making fasteners for sand core masses - Google Patents

Description

In the production of casting, mainly drying oils are used as anchors for sand cores. The disadvantages of drying oils are: their high gas working ability, high temperature, the need for drying the rods, and the long duration of drying.

A method is proposed for the manufacture of a fixative for sand core masses based on carbamide resins by dissolving crystalline urea in formalin containing urotropin admixture. The solution is heated to boiling and neutralized by cooling with ammonia. From the mixture obtained, caroamide resin is separated by known techniques.

Ammonia is used in the manufacture of a resin to bind free formaldehyde and stabilize the resin. Such resin may be stored 5; and transported in wooden or glass containers for up to 4 months without a significant change in properties.

If it is necessary to lower the drying temperature of the rods below 100 ° (to 20-60-), a hardener is added to the urea resin before manufacturing the core mixture, for example, sodium phosphate, ammonium chloride or ammonium sulfate, Petrov contact, lactic acid or any other KHCJibm hardener in an amount of from 2 to 15. (from the weight of the resin.

Rods with irimenepia as a carbiticum resin fixer and its mixtures are obtained with high mechanical strength up to 12kg / sl1, low gas-forming ability and no smell of formaldehyde.

The process for obtaining carbamide resins is very simple and available for the conditions found in the workshop.

Examples are cooked; Yeni carbaloid resins and rod masses:

PRI me R. I, Cooking with s oly

Berets 100 weight parts pure urea crystalline and solution 223

It is found in 250 parts by weight of 37% formalin with an admixture of 10 parts by weight of technical urotropine.

The solution is heated to boiling, maintained at boiling for 30-40 minutes, after which it is cooled and neutralized with ammonia to PH - 7.2-7.8. The consumption of 15% ammonia is about 30-80 parts by weight.

Example II Preparation of core mixture

The resin solution, diluted or not diluted with water, is mixed with pre-moistened sand in runners or other mixers for 10-20 minutes. The dose of the resin liquid solution is 1-3% by weight of sand, depending on the requirements of the rods.

From the resulting core mixture, the cores are molded in the usual way and dried at a temperature of 180- 200 °.

When cooled, the rods are ready for use.

P rome nil

To the resin obtained by the method described above, as a diluent, plasticizer, etc., are added, for example, sulphite bard, casein solutions in ammonia, synthetic or natural latexes, glyptal resins, glycerin.

The dose of these substances, depending on the requirements for the rods, can range from 1 to 75% by weight of the resin.

A resin mixed with one or more of the listed substances is added to the core mixture in an amount of 1-3% by weight of the applied sand. Molded rods are dried according to the mode specified in example P.

Example IV |

Any carbamide resin is pre-dried in a Krause spray dryer. The resulting powdered resin is mixed on runners with sand in an amount of 0.5-1.5% by weight of the sand. Sand should have a moisture content of up to 5%.

Further, the manufacturing process of core masses is carried out as indicated in Example II,

Subject from. bratis

A method of making a fixer for sand core masses based on carbamide resins, wherein crystalline urea is dissolved in formalin containing urotropin admixture, the mixture is heated to boiling and, after cooling, neutralized with ammonia, after which the resin is separated by known techniques.