SU926842A1 - Antisticking ink for molds and cores - Google Patents

Description

Fused quartz in the following ratio of ingredients, May. %:

Fused quartz67.0-71.4 Polymethylphenylsiloxane resin1.8- 2.5 Polyvinylbutyral0.9- 1.4 Acetic acid0.3-0.6 Technical Acetone10-12 Synthetic ethyl EthylOstal

Polymethylphenylsiloxane resin K-9 (TU6-02-907-74) is a white powder, well soluble in acetone, possessing high heat resistance, is used as a bond for suspension with various fillers. When used as a lacquer, it does not form strong films on particles of a refractory filler introduced into the lacquer. When introduced into the paint together with other polymers, the strength of the films is bound, it increases.

Polyvinyl butyral (PVB) is an adhesive dry (GOST 9439-73) white powder, soluble in 646 solvent or ethyl alcohol and not soluble in acetone. When introduced into the paint in small amounts together with another polymer of high heat resistance, it acts as a stabilizer (surfactant substance) of the bonding film; In the presence of various acids (including acetic acid) in PVB solutions, the slow process of polycodensation (structuring) proceeds with an increase in the viscosity of the solution, and consequently, with an increase in the sedimentation stability of the suspension.

Ethyl synthetic alcohol (GOST 11547-76) is a clear liquid with high dissolving power and rather low viscosity.

Technical acetone (GOST 2768-69) is a clear liquid, used as a solvent, which has a high dissolving ability for many polymers, including with respect to binding K-9 (1.5 times higher than the dissolving capacity of ethyl alcohol) , and low viscosity (4 times less than the viscosity of ethyl alcohol and 2 times less than the viscosity of toluene - the main component of the solvent 646).

Due to the low viscosity in non-stick paints, a better distribution of the binder on the refractory filler grains is achieved, which means a higher durability of the coating, its adhesion to the mold material, and better penetrating and covering ability of the foundry paint. Acetone mixed with solvent 646 forms a combination of solvents (acetone is polar, and toluene, which is the main component of solvent 646, is non-polar), i.e. the medium in which the structural-mechanical stabilization of polymer films most fully develops. binder (K-9) and stabilizer (PVB), resulting in high sedimentation stability of the suspension.

Acetic acid 98% (GOST 61-75) -white liquid, when introduced into polymethylphenylsiloxane resin K-9 causes a slow process

its polycondensation, i.e., acts as a hardening catalyst.

Fused silica with a vitreous content of at least 95% silicon dioxide, is obtained

by fusing quartz glass sand at 2000-2200 ° C and then crushing the lump to a state of powdered white powder with a grain size of not more than 0.15 mm.

Comparison of the properties of zircon concentrate and fused quartz shows that, due to the smaller bulk mass of fused quartz (more than 2 times lighter than zircon), introducing it into the suspension instead of

zircon (in the same amount) allows to obtain the same high rates of sedimentation stability of the suspension without the use of aerosil emulsifier; and a little less than average

the linear expansion coefficient of fused silica in combination with its property of softening (to acquire plasticity) at temperatures above 1000 ° C contributes to obtaining a dense protective

crusts of the coating without cracks and delaminations even in the most thermally loaded nodes of the mold.

Cooking nonstick paint

begins by displacing the dry components. Fused quartz, resin K-9 and Polyvinyl butyral are loaded into the mixer in the required ratio and mixed for 20-30 minutes. Wherein

a conglomerate of polymer particles of resin K-9 and PVB envelops the particles of fused silica, i.e., the process of inflowing polymers (binder and stabilizer) to the refractory filler takes place.

In a separate container, a combined solvent (ethyl alcohol-acetone) is prepared in the ratio determined by the paint composition.

The mixture of dry components is introduced into the combined solvent while stirring the medium in a paddle mixer at 30-40 rpm for 30-40 minutes until a homogeneous

suspension density. Acetic acid is introduced in a predetermined amount into the prepared suspension immediately before it is put into use. The compositions and properties of the paint according to the invention are shown in Tables 1 and 2.

Table 1 Paint is applied to the surface of the molds.

and rods with a brush or spray.

To obtain thin-walled castings, the paint is applied in a single layer, the density of the paint 5 being 1.9-2 g / cm.

For large thick-walled castings, the paint is applied in two layers, while the density of the first layer (penetrating) is 1.6-1.7 g / cm, and the second one is 1.9-10 2 g / cm 3.

The drying time of the paint in air is determined from the moment the sample is painted to the time it is acquired with a layer of transportable transportable coating, when there is no mortar on the surface when transferring the sample manually or by mites. For all paints, the drying time is within 16-28 minutes.

table 2

As can be seen from table 2, composition No. 2 is optimal (the paint has better sedimentation stability).

On castings made using the paint according to the invention, in all cases, burns are easily removed using a pneumatic tool after heat treatment of the castings. When used in thermally loaded nodes, there are separate inclusions of burns, which, after heat treatment, are easily separated in the process of shot-blasting cleaning and for its separation no manual treatment with pneumatic tools is required.

The implementation of the invention will increase the strength and heat resistance of the paint while maintaining its high sedimentation stability, as well as reduce the cost of paint, improve sanitary and hygienic working conditions and reduce burnout on massive castings.

Claims (2)

1. USSR author's certificate Yao 384595, cl. B 22 C 3/00, 1971. 2. USSR author's certificate for application No. 2534151 / 22-02, cl. B 22 C 3/00, 1977.