CS215406B1 - Foundry binder - Google Patents

Description

The invention relates to a foundry binder based on an alkali metal silicate solution, which is useful in all systems of self-curing core and molding compositions cured with powder or liquid hardeners.

Hitherto known binders of self-curing core and molding compositions based on an alkali metal solution, such as water glass, treated with, for example, starch hydrolyzate, powdered starch, sulphite leach, molasses and the like, or in combination with other substances such as cellulose derivatives acids and the like can be advantageously used in systems cured with powdered hardeners containing calcium silicates or liquid hardeners based on aldehydes or organic esters.

However, their disadvantage is that in order to achieve a sufficiently rapid increase in the strength of the molding compositions and a sufficient amount of their handling and final strengths with time, they must be; the content in the mixture is very high, eg 6.5 to 9% in a calcium silicate cured system or, for example, 4.5 to 6% in a liquid aldehyde-based hardener system. This also results in a simultaneous increase in the content of both types of hardener. Moreover, these binders cannot be used at all in the formulations of the curing compositions based on organic ester liquid curing agents, or the technological parameters of these mixtures, such as their surface quality and strength, are not operationally sufficient. There are also known waterglass binders adapted for molding compositions with liquid esters based on organic esters whose content in the mixture may be reduced to 3 to 3.5%, but these binders, on the other hand, do not comply with a mixture of liquid alcohols of a number of aldehydes and for mixtures with calcium silicates, it does not allow the reduction of their high content in the mixture. In addition, none of the known waterglass binders removes the typical drawbacks of liquid hardener formulations, which are long plasticity intervals even at relatively high compressive strengths, resulting in deflections, deformations and fractures of higher weight cores.

The above-mentioned drawbacks are overcome by the alkali metal silicate foundry binder according to the invention, which comprises from 0.1 to 10% glycols, the glycol being mono-, di-, tri and polyethylene glycol or a combination thereof.

By mixing the glycols with alkali metal silicate solutions already during production, i.e. before mixing with quartz sand and before adding any hardener, eg cement slag or liquid hardeners, they can also react perfectly to form a homogeneous, structured solution the binders of the hitherto unknown effect, i.e., the molding compositions with the binder according to the invention, at a reduced loading rate, achieve 40 to 70% higher compressive strengths compared to molding compositions with untreated waterglass.

The foundry binder prepared according to the invention satisfies equally well all binder systems, i.e. cured powdered calcium silicate hardeners or liquid hardeners based on esters or aldehydes, regardless of the weight of the molds or cores produced. It reduces the plasticity interval of the molding compositions to an operationally negligible minimum, thus avoiding deflections, deformations and fractures of the more massive and complex cores or molds.

I Long-term operational tests have shown that; The self-curing mixtures with the binder according to the invention achieve, with all types of hardeners, sufficiently fast growth of strength with time and sufficiently low abrasions, even when the binder content in the mixture is reduced. ! For example, in a curing composition cured with liquid aldehyde-based hardeners such as glyoxal, the binder content of the invention can be reduced by 1 to 2.5% while reducing the hardener content by up to 5%, and the curing composition cured with calcium sulfates can be reduced of the invention by 0.5 to 1%, the abrasion of the mold or core surfaces being reduced by 15 to 20%.

If an exceptionally high quality surface of the molds or cores is required, 0.1 to 0.9% starch hydrolyzate may be added to the binder of the invention.

Example of binder production according to the invention:

1. sodium water glass ......... '. 95% diethylene glycol ........... 4% water ........... 1%

2. Sodium water glass .......... 95% mixture of di- and triethylene glycol (2: 1) .. 1%

Claims (1)

SUBJECT Foundry binder based on both silicate and alkali metal solutions, characterized in that it contains from 0.1 to 10% glycols, i.e. monoethylene glycol, diethylene215406 and starch hydrolyzate solution. . . . 0.9% J water ................ 3.1% The binder is prepared in a mixing vessel equipped with an efficient mixing device by first dosing water glass and adding diethylene glycol and water with vigorous stirring. The course of reactions is! can be accelerated by raising the temperature up to 100 ° C. The specific weight of the resulting binder is e.g. , An example of the composition of a molding composition with a binder according to the invention is also quartz sand. 100 wt. 3 parts by weight of the binder according to the invention. parts' Liquid ester-based hardener i. 0.3 wt. parts The molding mixture is prepared on a special continuous mixer with an output of 101 mixture / h by simultaneously adding together with quartz sand a binder and an ester-based liquid hardener into the mixer. The molding mixture thus prepared is continuously discharged into jade or molds where and after about 40 minutes of spontaneous solidification, it reaches a handling strength allowing disassembly of molds or jars and preparation for final casting. i Comparison table of crushing strength of molding _; i mixtures: I j Molding The molding material mixture even with a binder in accordance with a conventional water ^[! invention glass; ! time in minutes strength in kPa 40 660 560 60 1 060 715 J20 1 160 1 080 240 1 840 1 510 24 h 2 500 1 830 OF THE INVENTION glycol, triethylene glycol, polyethylene glycol or combinations thereof.