AU2005203130A8

AU2005203130A8 - Binding agent system based on water glass

Info

Publication number: AU2005203130A8
Application number: AU2005203130A
Authority: AU
Inventors: Thomas Steinhauser
Original assignee: Minelco GmbH
Current assignee: LKAB Minerals GmbH
Priority date: 1999-10-29
Filing date: 2005-07-19
Publication date: 2008-09-11
Anticipated expiration: 2019-10-29
Also published as: AU2005203130B2; AU5713999A; AU2005203130A1

Description

I

P001 Section 29 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Binding agent system based on water glass The following statement is a full description of this invention, including the best method of performing it known to us: 1 -2- Binding agent system based on water glass SDescription ^C The invention relates to a binder for producing core moul- Sdings for foundry purposes.

Binders form part of a moulding material which, under certain conditions such a moistening, swelling and silicate formation, ensures the bonding between the individual grains of sand. Apart from pure swelling binders and ceramic binders, use is also made of chemical binders based on water glass or on synthetic resin, which binders react to one another and harden in the process.

Prior art binders are either not sufficiently stable or they have undesirable side effects and/or generate waste products which place the environment at risk. It has therefore been found that an advantageous comprise consists in moulding materials which, via dehydration, form solid phases and harden in the process. However, it is not always easy to control the hardening processes in such a way that they first occur in the core box. Especially in modern core forming machines, there exists a risk of early hardening of the moulding sand. In consequence, the required good flow properties of the sand while flowing into the core box are not always achieved.

It is the object of the present invention to develop a binding agent additive for moulding sands, which additive has the desired properties and, in particular, is suitable for being used in core moulding machines.

In accordance with the invention, the objective is achieved 3 O by the characteristics listed in the Claims.

The new binding agent system based on water glass consists n of an aqueous alkali silicate solution of the general com- C positiont xSiO0 x yM 2 O x zH 2 O, with M representing the alkali ions Li* K* or Na* and is characterised in that it additionally contains a hygroscopic base. In an advantage- Sous embodiment, the hygroscopic base is provided in the n form of a sodium lye in the ratio of 1 4 to 1 6. If the C modulus of Na20/SiOz amounts to 2.5 to 3.5 with a solid Ssubstance content of 20 to 40 it is possible, under any C operating conditions, to prevent the moulding sand from hardening prematurely. According to a preferred embodiment it is proposed to provide the hygroscopic base in the form of a 30% sodium lye in an aqueous solution. To be able to control the hygroscopic properties, it is preferable to use a surface-active substance. If the surface-active substance is added to the binding agent system in the form of silicone oil with a boiling point of 250 the flowing ability of the moulding sand can be improved considerably. In an advantageous embodiment, an emulsion solution with 8 to silicone oil with reference to the quantity of binder is added to the binding agent system.

Below, the invention will be explained in greater detail with refernce to a comparative example, using a core moulding machine according to Figure 1, which is designed as follows: The core moulding machine consists of a vertically arranged housing A to which there is flanged a horizontal air inlet B. The air inlet is controlled by an air inlet valve 1 with a large surface, and there exists an increased air pressure in the air storage tank 5. When opening the air inlet valve 1, the air pressure reaches the machine chamber 10 of the housing A, in which chamber 10 there is vertically arranged a slotted sand cylinder 6. The sand cylinder 6 is connected to a sand storage container 3 which can be emptied via a slide 4.

-4- V~ When the air inlet valve is actuated, sand is conveyed from the slotted sand cylinder 6 into the moulding head 7 with the sand exit opening, and enters the core box 8, with a Score sand ventilator 9 ensuring the compaction of the core Ssand 11.

To be able to assess the moisture content of the moulding sand, a moisture measuring device is integrated into the T air exit valve 2. By using this assembly, it was found that 0 the moulding sand in accordance with the invention achie- I ved much higher moisture contents and thus an improved Sviscosity and an improved flowing ability of the moulding CA sand.

Claims

1. A binding agent system based on water glass, consi- vsting of an aqueous alkali silicate solution of the general composition: xSi02 x yM20O x zH 2 0, with M re- presenting the alkali ions Li*, Kor Na*, characterised in that the binding agent system additionally contains a hygroscopic base.

2. A binding agent according to claim 1, characterised in that the hygroscopic base is added in the form of a sodium lye in the ratio of 1 4 to 1 I 6.

3. A binding agent system according to any one of the preceding claims, characterised in that the modulus of Na 2 O/SiO 2 amounts to 2.5 to with a solid substance content of 20 to

4. A binding agent system according to any one of the preceding claims, characterised in -6- In that the hydroscopic base is added in the form of a 30% sodium lye in an aqueous solution.

A binding agent system according to any one of the Co preceding claims, characterised in that for the purpose of controlling the hygroscopic 0 properties, there is added a surface-active substance.

6. A binding agent substance according to any one of the C preceding claims, characterised in that the surface-active substance is added in the form of silicone oil with a boiling point of _>250

7. A binding agent system according to any one of the preceding claims, characterised in that there is added an emulsion solution with 8 to silicone oil relative to the quantity of binding agent. DATED this 19th day of July 2005. VAW aluminium A.G. WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN. VIC. 3122.