SU1090482A1 - Moulding sand for producing shell moulds and cores in heated tooling - Google Patents

Abstract

1. MIXTURE FOR PRODUCING FOUNDRY CORES AND shell mold IN HEATED tooling comprising a refractory filler and novoldChnuyu resol phenol resin and an anti-friction additive, differing ayuscha in that, to reduce the length of cure and reduce the tendency of shell molds and cores flaking, and also increase their strength in the hot state; the mixture contains oligomer with lUHsii as a Novolac phenol-formaldehyde resin; “LLTKZ); i, K; tavi i ik ' iJ iOIi 4 with a molecular weight of 300-500, modified with a mixture of carboxylic fatty acid and aromatic sulfonic acid, taken in a mass ratio

Description

The invention relates to a foundry industry and relates to mixtures based on phenol-formaldehyde resins intended for the manufacture of shell molds and cores in a heated tooling. A mixture containing a refractory filler, novolac phenol-formaldehyde resin, together with hexamine and technological additives, is known, and the bond is used as a solution in an organic solvent f1 1. When the metal is poured into molds from this mixture, you emit a large amount of nitrogen-containing volatile substances , resulting from thermo-oxidative destruction of hexamine, which leads to the formation of sieve porosity in castings. Also known is a mixture containing a refractory filler, phenol-formaldehyde novolac and resole resins, water-wax dispersion and hexylene C 21. Methenamine is also used as a hardener in this mixture, therefore the task of eliminating the harmful release of nitrogen-containing substances during the pouring of metal forms is not solved. It is not possible to exclude urotropine from the composition of this mixture, since this sharply deteriorates the strength characteristics of the mixture in a hot state. The closest to the invention in its technical essence and the achieved result is a mixture for the manufacture of casting shell molds and cores in a heated equipment Gz, containing a refractory filler, novolac and rezol phenol-formaldehyde resins and antifriction additive in the form of calcium stearate with the following ratio of components, wt.%: Novolac resin 0 , 9 Resolna resin 2.1. Calcium stearate 0.1-0.5 Refractory filler Others In the Czj mixture, the mass ratio between rezol and novolac resins is 70:30. When the metal is poured into molds made on the basis of this mixture, there is no emission of nitrogen-containing volatile substances. However, the strength characteristics of this mixture in hot condition are low due to the high content of resole resin. It is not possible to increase the content of novolac resin, since the curing of the novolak in this composition is due to the metnol groups of the resole resin, and as the amount of novolak is increased, an uncured resin per composition is obtained. The mixture is also characterized by a low cure rate, as a result of which is long. The low rate of curing of the shell molds and cores causes an increased scrap during their manufacture due to peeling at the moment of removing excess uncured mixture. The aim of the invention is to reduce the duration of curing and reduce the tendency of shell molds and cores to peel off, as well as increase their strength in a hot condition. To achieve this goal, the mixture is used to make foundry shell molds and cores in a heated snap-in, including refractory filler, novolachnaya and resol phenol-formaldehyde resins and antifriction additive, contains as a Novolac phenol-formaldehyde resin an oligomer with a molecular weight of 300-500, modified by The fatty acid carboxylic acid and aromatic sulfonic acid taken in a mass ratio of (320): 1 with the following ratio of ingredients, wt,%: Novolac phenol-formaldehyde resin in the form of an oligomer with a molecular weight of 300-500, modified with a mixture of carboxylic acid fatty and aromatic sulfonic acids, taken in a mass ratio of (3-20): 1 Phenol-formaldehyde resole resin Antifriction additive Fireproof floor; The rest As an antifriction additive, the mixture contains a water-wax dispersion with a wax content of 40-44 wt.% Of dry residue. Introduction to Novolac Resin Mixture c. The noted features allow, due to its high reactivity, to increase the content of the resin resin in the composition of the mixture and to implement such conditions for the correlation of the Novolac and Resole resins, under which, due to the combined action of the mechanisms of thermal and acid curing, a compacted mesh of spatial polymer is formed. Therefore, the proposed mixture has high strength properties in a hot state without the use of urotropin in the composition of the plated mixture. At the same time, gas-mixing of the mixture decreases and, accordingly, the surface quality of the castings is improved due to the elimination of scrap and sieve porosity. Ball samples made from these mixtures contain in the surface layer of nitrogen at the level of the prototype. The increased reactivity of the novolac resin provides rapid curing and uniform shell strength over the cross section, while the tendency of the shell mold to peel off when removing excess mixture is significantly reduced. The necessary properties of the mixture can be achieved only by modifying the novolac resin with a carboxylic acid of a fatty series and with an aromatic sulfonic acid in aggregate at their mentioned weight ratio. Adipic acid, salicylic acid, succinic acid, glutaric acid, anthronic phenylenthranyl sulfonyl acid, maleic acid, H-hydroxybenzoic acid and other acids, which are characterized by the addition of a polar functional group to the carboxylic group (-NKL - OH, -COOH). Benzosulfonic acid, p-toluenesulfonic acid and others can be used as an aromatic sulphonic acid. Wavelength resin with molecular weight less than 300 is celled during transportation and storage. which necessitates the introduction of an additional crushing stage before its use. A resin with a molecular weight greater than 500 has a high viscosity, which is why it is poorly distributed over the surface of sand grains, which requires increased consumption to provide the required 1x strength properties of the mixture. When the mass ratio of the fatty carbonic acid and aromatic sulphonic acid is more than 20: 1, the process of polycondensation of phenol with formic aldehyde leads to the formation of a resin with a molecular weight of more than 500. At a mass ratio of the carboxylic acid of the fatty series and aromatic sulphonic acid, less than 3 : 1 with polondensation of phenol with formaldehyde-. a resin with a molecular mass of less than 300 is formed with a guide, which has a low reactivity, as a result of which the strength characteristics of the mixture are low. When the content of the novolak in the mixture is less than 1.5%, the strength characteristics of the mixture and the rate of its curing are low, which results in a prolonged scrap due to flaking at the time of removal of excess uncured mixture. When the content of novolak in the mixture is more than 4.2%, the resole resin ceases to act as a curing agent in relation to the novolak, and the mixture becomes unsuitable for use. A water-wax dispersion with a dry residue content of 40-44 wt.%, Used as an antifriction additive, prevents caking and clodiness of the packaged mixture during storage and improves its flowability. Novolac phenol-formaldehyde resin used in the proposed mixture is obtained as follows in a way. In a three-necked flask equipped with a stirrer, phenol, formaldehyde in the form of a 37% aqueous solution, carboxylic acid, and hydrochloric acid in the form of a 7.25% aqueous solution are loaded in the required amount. The reaction mixture is heated to boiling, maintained at a boiling point of 40-60 minutes, the required amount of sulphonic acid is introduced, then cooled to and the vacuum dryer is carried out to a dropping temperature of 75-95 ° C. The proposed method provides a 300-500 molecular weight Novolac resin. The plated mixture is prepared as follows. The sand, heated to, is mixed in a mixer with a novolac resin for 30-60 seconds, then a liquid resol resin is added, alternated for 15 seconds. A water-drip dispersion is then introduced and stirring is continued until the mixture becomes free-flowing. Total cladding cycle for 3 min. The compositions of the clad mixtures are given in Table 1. The technological properties of the plated mixtures 1–4 are given in Table. From the Table 2 table it follows that the use of a Novolac resin, modified in the composition of the clad mixture

Table 1 26 of a mixture of fatty carboxylic acid and aromatic sulfonic acid in a weight ratio of 3: 1 20: I in combination with a cutting resin and with an optimum ratio of components allows to obtain a more favorable complex of properties of the clad mixture as compared to the prototype: strength in mountains as the state increases 1.3-2.2 times, the peeling force increases 2.8-7.3 times, the duration of the curing cycle of the curing is reduced 1.4-1.5 times, the quality of the surface of the castings does not deteriorate. The expected economic effect is 5.3 rubles. for 1 ton of good to pour.

Quartz sand On 2K016A

Novolac phenol-formaldehyde resin (modified with a mixture of acids) with molecular weight

300 400 500

Phenol formaldehyde resin

SFZH-3032 1.55 brands

ANN NEMODIFICIERS Novolachna phenol-formaldehyde resin Water-wax dispersion 0, 50

Calcium Stearate

96.60 9-6.50

1.50

1.80 2.10

0.21

0.90

0.90

0.10

0.50

Strength at hot stretching, mPa2.9

Peel force (pull-off force of uncured shell), MPa 0.22

Thickness formed

for 15c shell, 7.3 mm

0.02 0, -03 0.03 0.02

table 2

Claims (2)

1. MIXTURE FOR MANUFACTURE OF CASTING SHIELDS AND RODS IN HEATED EQUIPMENT, including refractory filler, novolac and rezol phenol-formaldehyde resins and an antifriction additive, characterized in that, in order to shorten the curing time and increase the core and reduce the incline their strength in the hot state, the mixture contains, as novolac phenol-formaldehyde resin, an oligomer with a molecular weight of 300-500, modified with a mixture of carboxylic acid a power series and aromatic sulfonic acids, in a weight ratio of (3-201: 1, with the following ratio of ingredients, wt.%: Novolac phenol-formaldehyde resin in the form of an oligomer with a molecular weight of 300-500, a modified mixture of fatty carboxylic acid and aromatic sulfonic acid, taken in a mass ratio (3-20): 1 1.5-4.2 Resol phenolophore ¹ maldehyde resin Anti-friction additive Refractory filler 0.2-1.8 0.1-0.9 Rest 2. The mixture according to claim 1, characterized in that as an antifriction additive it contains a water-wax dispersion with a wax content of solids AO44 wt.%.