AU741268B2

AU741268B2 - Method and apparatus for supplying an optimised quantity of catalyst to a core shooting machine

Info

Publication number: AU741268B2
Application number: AU75421/98A
Authority: AU
Inventors: Christoph Genzler; Heinz Josef Hemsen
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 1997-06-04
Filing date: 1998-05-22
Publication date: 2001-11-29
Anticipated expiration: 2018-05-22
Also published as: DE19723314C1; EP0986442B1; CN1265614A; WO1998055249A1; AR015384A1; KR20010013424A; ATE234698T1; JP2002502317A; CA2293507A1; TW396075B; DE69812354D1; EP0986442A1; BR9809723A; TR199902962T2; AU7542198A; ZA984468B

Description

WO 98/55249 PCT/GB98/01509 METHOD AND APPARATUS FOR SUPPLYING AN OPTIMISED QUANTITY OF CATALYST TO A CORE SHOOTING MACHINE This invention relates to a method and apparatus for the supply of an optimised quantity of catalyst to a core shooting machine for the manufacture of cores and moulds for casting processes wherein the catalyst is extracted from a pressurised vessel in liquid or gaseous form and is mixed with a purging gas before it is introduced into the core shooting machine.

Methods are known for the manufacture of cores for casting processes. The application of amines as catalysts for the manufacture of cores according to the urethane Cold Box Process is described in the special issue of Giesserei 78 (1991), volume 11, pages 372 to 374. In this known method for core and mould production a moulding material is used containing a benzyl ether resin (ortho-phenol resol) and an isocyanate which is cured with a tertiary amine catalyst. As the catalytic effect of the amine is particularly advantageous in the gaseous phase, tests were carried out using trimethylamine (TMA) whose boiling point is about 3 OC, and with which, for this reason, curing is possible in a relatively simple manner with a gaseous amine. The accelerating effect of a tertiary amine by the formation of reactive transitional compounds during the polyurethane reaction is described by the following reaction equation -RN=C=O (CH 3 3 N Isocyanate TMA (+)(CH3)3 OH-R'-OH

N(CH

3 3

N(+)(CH

3 3

OR'-OH

Polyol Polyurethane WO 98/55249 PCT/GB98/01 509 2 When making cores by this known method it is disadvantageous that the tertiary amine is fed to the core shooting machine considerably in excess of the required amount. Although it has been shown that the application of trimethylamine makes it possible to advantageously reduce the amount of amine used by about 50% in comparison to other amines, the application of trimethylamine still has associated disadvantages. One problem is the extreme nuisance created by the odour which makes it essential that all parts of the equipment used are absolutely leak proof. All pipework must there be insulated at relatively high expense.

A method for the manufacture of cores for casting processes is described in DE 19706472.8 in which gaseous trimethylamine is conducted through parts-of a metering device and then, in a concentration of from 0.01 to 0.12 wt-% based on the quantity of sand used per core, it is conducted into the core shooting machine, and is there brought into contact with the sand.

According to a preferred embodiment of this method it is envisaged that the gaseous trimethylamine is exposed to a purging gas. In general according to the method described in DE 19706472.8 it is envisaged to take the trimethylamine from a pressurised vessel and conduct it to the core shooting machine by means of a conduit. A connector is located in the conduit for the purging gas which in this manner is brought into contact with the catalyst. However it is disadvantageous when using this method that the quantity of catalyst which is conducted to the core shooting machine decreases as a result of a decrease of the pressure in the pressurised vessel. Therefore the addition of and/or the setting for an optimised quantity of catalyst is not possible. Furthermore, it is disadvantageous that the pressure at which the mixture of catalyst and purging gas is conducted to the core shooting machine is relatively low, as it is not possible to conduct the mixture of catalyst and purging gas through the core shooting machine at the desired speed.

The object of the invention therefore is to provide a method and apparatus for adding an optimised quantity of catalyst to a core shooting machine for the production of cores or moulds for casting processes in which it is ensured that the core shooting machine is exposed to the optimised quantity of catalyst in the. shortest possible time.

According to the invention there is provided a method for the supply of an optimised quantity of catalyst to a core shooting machine for the manufacture of cores or moulds for casting processes in which a catalyst is extracted from a pressurised vessel in liquid or gaseous form and is mixed with a purging gas before it is introduced into the core shooting machine, wherein firstly an optimised S quantity of catalyst and secondly the purging gas at a pressure of 0.1 to 10 bar are fed into a pressure container, the pressure container is then closed so that the :i catalyst and purging gas are mixed in the pressure container, and the resulting S mixture is introduced into the core shooting machine.

As used herein the term "core shooting machine" shall be understood to see.*: include devices or apparatus used in foundries for the manufacture of moulds for casting processes.

*so• The catalyst may be* for example a tertiary amine (such as trimethylamine), methyl formate, sulphur dioxide or carbon dioxide. The method is particularly useful for producing cores or moulds using a benzyl ether resin and an isocyanate and a tertiary amine such as triethylamine as catalyst.

A gas bottle may be used for example as the pressurised vessel containing the catalyst. Usually air is used as the purging gas but other gases, for example carbon dioxide, may be used. The supply of purging gas to the pressure container at 0.1 to 10 bar makes it possible to adjust the pressure in the pressure /ontainer within the range from 0.1 to 10 bar. Advantageously the catalyst supply takes 4e through a valve. The optimised quantity of catalyst WO 98/55249 PCT/GB98/01509 4 depends on the size of the core or mould being produced, and is determined in advance on the basis of various parameters for a particular core or mould.

Surprisingly it has been shown that in the process of supplying an optimised quantity of catalyst to a core shooting machine according to the invention it is possible in advantageous manner to conduct the optimised quantity of catalyst through the core shooting machine in an optimised time. The relationship between the quantity of catalyst on the one hand, and the quantity of purging gas on the other hand, which is adjusted to between 1 1000 and 1: 10000 can be held constant while the mixture of the two is flowing through the core shooting machine. In this manner disadvantageous variations in pressure may be avoided. The optimised time is the shortest time which is necessary for the mixture to flow completely through the core shooting machine, and it is regulated by means of the pressure in the pressure container.

In a preferred embodiment of the method of the invention the catalyst in gaseous form is heated in the pressurised vessel to 3 to 80 OC to facilitate contact between the catalyst and the purging gas.

According to another preferred embodiment of the method of the invention the catalyst is conducted to metering bellows in liquid form before being fed in gaseous form to the pressure container. The use of the metering bellows is advantageous because although heat is extracted from the surroundings during the transformation of the catalyst from the liquid to the gaseous form the metering bellows remain able to continue to function .over extended periods of operation when compared with other conveying equipment. It is particularly advantageous that the metering bellows can be installed in a relatively simple manner because older core or mould production plants can be adapted to use this embodiment of the method of the invention.

According to a further preferred embodiment of the method of the invention trimethylamine is used as the catalyst, and it is advantageous that when using trimethylamine the quantity of catalyst can be kept relatively.small because the nuisance from odour when cores are subsequently stored before use can largely be avoided.

According to a further preferred embodiment of the method of the invention, after the mixture of catalyst and purging gas have been introduced from the pressure container into the core shooting machine additional purging gas is fed into the core shooting machine via the pressure container. This measure has the additional advantage that it results in purging of the core shooting machine, and the core or mould, and appreciably reduces any nuisance due to the odour from the catalyst.

o According to a further feature of the invention there is provided apparatus for the supply of an optimised quantity of catalyst to a core shooting machine for the manufacture of cores or mould for casting processes comprising a S pressurised vessel for containing the catalyst, means for determining the quantity of catalyst in the pressurised container, means for conducting the catalyst to a conduit for supplying the catalyst to a core shooting machine, and means for supplying a purging gas to the apparatus, wherein the apparatus also has a pressure container located between and connected to the pressurised vessel and the supply conduit, and the purging gas supply means is connected to the pressure container, the apparatus further comprising valves to close the pressure S* container, so that an optimised mixture of catalyst and purging gas present in the pressure container may be introduced into the core shooting machine.

If desired the apparatus may also have a heater for heating the catalyst in the pressurised vessel.

Such apparatus is suitable for use when the catalyst in the pressurised sel is in gaseous form. When the catalyst in the pressurised vessel is in liquid form the apparatus may have metering bellows located between the pressurised vessel and the pressure containei so that the catalyst may be transformed into the gaseous form before being fed into the pressure container.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:- Figure 1 shows schematically apparatus used for producing cores of moulds by a known method in which a catalyst is exposed to purging air.

Figure 2 shows schematically apparatus according to the invention for supplying an optimised quantity of catalyst to a core shooting machine using the method of the invention and Figure 3 shows schematically apparatus according to the invention for o1.: 15 supplying an optimised quantity of catalyst to a core shooting machine using the method of the invention, wherein the catalyst is used in liquid form.

Referring to Figure 1, a catalyst is contained in a pressurised vessel which may be a simple gas bottle, and the pressurised vessel is located 20 on scales in order to determine its contents. The pressurised vessel can oo be heated by means of heater In the production of a core or mould the S. catalyst is conducted through a valve into supply conduit which leads ooodirectly to the a core shooting machine (not shown). A purging gas is introduced directly into the supply conduit through conduit With decreasing pressure in the pressurised vessel the quantity of catalyst which reaches supply conduit is reduced. Furthermore, in order to prevent the purging gas from being introduced into the pressurised vessel through the open valve the pressure selected in the conduit for the purging gas cannot be too great. The pressure which exists in the supply conduit is therefore insufficient to conduct the quantity of catalyst through the core shooting machine in as short a time as is S desirable.

Referring to Figure 2, a catalyst is contained in a pressurised vessel which may be a simple gas bottle, and the pressurised vessel (11) is located on scales (12) in order to determine its contents. The pressurised vessel (11) can be heated by means of heater A previously determined optimum quantity of catalyst is introduced via first valve (14) into pressure container (15) and first ,alve (14) is closed. Purging gas is supplied to the pressure container (15) through conduit (16) via second valve (17) at a pressure of 0.1 to 10 bar. Second valve (17) is then closed and third valve (18) is opened so as to introduce the mixture of catalyst and purging gas which is present in the pressure container (15) into supply conduit (19) and into the core shooting machine (not shown).

Figure 3 shows similar apparatus to that shown in Figure 2 but the apparatus also has metering bellows (20) an additional fourth valve (21) located between first valve (14) and pressure container (15) and there is no heater. When the apparatus is used liquid catalyst in the pressurised vessel (11) is conducted through S first valve (14) into the metering bellows (20) where the catalyst is transformed from the liquid to the gaseous state. First valve (14) is then closed and fourth valve (21) is opened, and the gaseous optimised quantity of catalyst is introduced into the pressure container while the second valve (17) and the third valve (18) remain closed. After the fourth valve (21) has been closed the second valve (17) is opened and purging air is introduced into pressure container The third valve (18) is then opened and the mixture of catalyst and purging gas is introduced to a core shooting machine (not shown) via supply conduit (19).

Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should It be taken as, an acknowledgment or any form of suggestion that that prior art sfo part of the common general knowledge in Australia.

Claims

1. A method for the supply of an optimised quantity of catalyst to a core shooting machine for the manufacture of cores or moulds for casting processes in which a catalyst is extracted from a pressurised vessel in liquid or gaseous form and is mixed with a purging gas before it is introduced into the core shooting machine, wherein firstly an optimised quantity of catalyst and secondly the purging gas at a pressure of 0.1 to 10 bar are fed into a pressure container, the pressure container is then closed so that the catalyst and purging gas are mixed in the pressure container, and the resulting mixture is introduced into the core shooting machine.

2. A method according to claim 1 wherein the catalyst in gaseous form is heated to 3 to 800C in the pressurised vessel. *0

3. A method according to claim 1 wherein the catalyst in liquid form is conducted to metering bellows before being fed in gaseous form to the pressure container. o" 0:00 20

4. A method according to any one of claims 1 to 3 wherein the catalyst is e trimethylamine.

A method according to any one of claims 1 to 4 wherein after the introduction of the mixture of catalyst and purging gas into the core shooting machine additional purging gas is fed into the core shooting machine through pressure container.

6. Apparatus for the supply of an optimised quantity of catalyst to a core shooting machine for the manufacture of cores or mould for casting processes comprising a pressurised vessel for containing the catalyst, means for determining CIAtt-the quantity of catalyst in the pressurised container, means for conducting the P:\OPER\Axd\75421-98spe doc-49/10/01 -9- catalyst to a conduit for supplying the catalyst to a core shooting machine, and means for supplying a purging gas to the apparatus, wherein the apparatus also has a pressure container located between and connected to the pressurised vessel and the supply conduit, and the purging gas supply means is connected to the pressure container, the apparatus further comprising valves to close the pressure container so that an optimised mixture of catalyst and purging gas present in the pressure container may be introduced into the core shooting machine.

7. Apparatus according to claim 6 wherein the apparatus has means for .heating the catalyst in the pressurised vessel.

8. Apparatus according to claim 6 wherein the apparatus has metering bellows located between the pressurised vessel and the pressure container so that the 15 catalyst may be transformed into the gaseous form before being fed into the pressure container.

9. A method substantially as hereinbefore described with reference to the accompanying drawings, excluding Figure 1. 2

10. An apparatus substantially as hereinbefore described with reference to the accompanying drawings. DATED this 9 th Day of October, 2001 Foseco International Limited by its Patent Attorneys ,4.2AVIES COLLISON CAVE