DE2331159A1 - PROCESS FOR MANUFACTURING CASTING MOLS AND CASTING CORES AND PROCESSLY MANUFACTURED PRODUCTS - Google Patents

Description

Dr.-i _nß . Dipi, Phy ₈ . OSKAR KÖNIG Patoni _& n-.valt

Deutsche Bank AG F - .. ·

Con "o No. 6: ί OC 3 <

TplefOP: (0711) 62 85 Gl '., "

'irWramm · Koerufpnt 7000 STUTTGART-I. Klüpfels.raße G Postscheck S.gt.64. , -

^p Poatfach 51

3335

AUTOMATISME & TECHNIQUE Arcueil (VaI de Marne) France

Process for the production of casting molds and casting cores as well as products manufactured according to the process.

The present invention relates to a method for the production of casting cores and molds as well as to molds and cores made using this process.

Various manufacturing processes for casting molds and casting cores are already known. There are two in these procedures To distinguish between categories: the so-called "Karmkasten" -

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Process and the so-called "Kaltkasteri process".

As far as the "hot box" method is concerned, it is particularly the "hot box" method in which a Mixture of sand and a liquid thermosetting resin and a hardening agent is used. Under the influence of heat (treatment at a temperature of 100 to 300 ° C for a certain period of time) the hardening the core or the shape achieved.

Another "warm box" process is called "croning" or "Shell Molding" processes.

According to this procedure, the sand is previously coated with a "Novclak" resin and a crosslinking agent (hardening agent) such as hexamethylenetetramine coated (mixed). Under the influence a heat treatment at 200-300 ° C, the mixture is hardened for a certain period of time.

The major drawbacks of these "hot box" processes consist on the one hand in the required heat consumption / to the temperature of the box during a certain time on the Bringing the above values and on the other hand in the resulting difficulties for handling the boxes.

_{The so-called “silicate CO 2} ” process has long been known as the “cold box” process. According to this process, the molding sand is mixed with a silicate and the core is hardened in such a way that carbon dioxide is passed through the sand-silicate mixture, which causes the binder to harden and fixes the shape of the product to be manufactured.

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Another "cold box" method is the so-called "ASHLAND" method. The mixture to be formed consists essentially of molding sand to which a resin is added, which under the influence of a catalyst such as Triethylamine or dimethylethylamine, is polymerizable. When the mixture into the molding cavity was introduced, passes, one in the same a gas, such as carbonic anhydride with the addition of a Catalyst a, whereby a rapid hardening of the polymerizable resin added to the mixture caused will.

This process offers numerous advantages (no temperature increase, Possibility of high production output), but also has serious disadvantages because the The catalysts used have an unpleasant odor and even a certain toxicity, which makes one forced will take precautions to prevent the curing gas from spreading in the atmosphere, as well because molding devices must be provided which ensure good distribution of the hardening gas, thereby complicating the construction of these devices will. . . . . "

Finally, in the "cold box" method, so-called. "Self-curing" process known. These procedures exist that the molding sand contains a binding agent, generally a synthetic resin, and a reactant, which is produced by a * multiple contact causes the binding agent to harden when »is mixed.

"-Ver be £ * lead either FTLE" These ^H Selbsthärtungs procedure »it slow" setting "when the nature

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of the binder used and the type or concentration of the reactant cause the curing to be slow occurs, or they are referred to as "rapid setting processes" when the choice of binder as well as the Choice of the reactant lead to rapid hardening.

However, the "slow setting" processes can only be used for very large parts that are not large Production output must be taken into account.

In contrast, the "rapid setting" methods can be used for small parts that require high production rates are required, but unfortunately the life of the prepared mixture is extremely short (a few seconds) and thus the risk of premature hardening in the nucleation facilities and the need for complete emptying of the core box after each filling process. These conditions make the application of the "self-curing" process with rapid Setting considerably restricted.

The invention aims to remedy these disadvantages of the known methods and in particular a "cold box" method to create with rapid self-curing, at which the life of the mixture compared to the known Process is increased considerably, so that this life is suitable for industrial series production and the It is possible to manufacture cores and molds, no matter how complicated their shape is and what number of cores or molds are in the same box, this process also having all the advantages of the "self-cure" process compared to the "hot box" process or hardening gas process maintains.

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To this end, the invention relates to a manufacturing method for casting cores and molds, which is characterized in that a mixture of molding sand, binder and Reactant prepares at low temperature and the mixture under this low temperature condition up to their introduction into the box and then this temperature influence no longer apply to the mixture.

According to the invention, it is particularly useful to make the process so that a mixture of molding sand, binder and a reactant at low temperature and under a controlled atmosphere and that this mixture under withstand these low temperature and controlled atmosphere conditions until they are placed in the box, then the Leaves cooling (air conditioning) and control of the atmosphere and possibly increases the temperature moderately.

In many cases it can be useful to expose the mixture introduced into the box to temperatures, which are moderately above normal room temperatures.

The purpose of the temperature increase that is made after the mixture has been introduced into the box is to provide the time for setting to decrease the mix. This increase in temperature is therefore only used when it is necessary to achieve the required To ensure production output and it is generally only low.

The control of the atmosphere can advantageously in general essentially consist in the possibilities of oxidation Eliminate mixture.

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The preparation of the mixture and the maintenance of its low temperature under a controlled atmosphere can be based on can be achieved in different ways. You can, for example, expediently air-conditioning devices or cooling devices use and introduce an inert gas into the air-conditioned or cooled enclosure. In the same way one can Introduce a certain amount of dry ice into the mixture preparation and storage enclosure, and at the same time the two desired effects, namely cold and controlled atmosphere can be brought about.

According to another feature of the invention, the preparatory process can and storage temperature of the mixture expediently be of the order of 4-5 ° C.

According to a preferred embodiment of the invention, this is Binder a synthetic resin, preferably a phenoplast, aminoplast, Polyester, purane resin or a mixture of such resins,

According to a preferred development of the invention, the reactant can be a hardener (hardener). This hardener can preferably be a compound that has an acidic organic or mineral or organo-mineral function

Below are some examples of such connections:

Example of a hardener with an acidic organic function; Paratoluenesulfonic acid

Examples of compounds having an acidic mineral function : phosphoric acid;

a salt, ζ. B. ammonium chloride, which is capable of releasing an acid.

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Example of a hardener with acidic organo-mineral

Function:

a combination or complex of an organic acid and a mineral salt, for example an organic one Acid and a mineral salt according to the preceding examples.

In a preferred embodiment of the invention wijd as Reagent a catalyst, preferably an amine, is used.

The invention is illustrated below with the aid of mixing examples which can be used to implement the process suitable:

1st example

You mix molding sand with a binder in the form of a synthetic resin, preferably a phenoplast, aminoplast, polyester, furan resin or a compound of these resins. Man gives a hardener with an acidic organo-mineral function at.

The preparation of the mixture and its storage up to the point of view their use take place at a temperature of under ^ r 5 ° C and under a neutral atmosphere, for example under a Nitrogen atmosphere.

The mixture is placed in a core box, its temperature is kept at approx. 45 ° C.

One minute after placing the mixture in the box the core can be removed from the mold and it has the desired Hardness and durability characteristics.

Pie used can be composed as follows: 100 parts by weight of white silicon sand; 0.8 to 3 parts by weight of binder; [A hardening agent of a weight which is 5 to 30 percent by weight of the weight of the binding agent.

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2nd example

Molding sand is mixed with a binder in the form of a synthetic resin and is a reaction or crosslinking agent, for example a polyisocyanate, and a catalyst, for example a tertiary amine.

During its preparation and storage, the mixture is kept at a temperature below 5 ° Γ and under an inert atmosphere then it is placed in a core box, the temperature of which is of the order of 45 ° C lies. The desired hardening is achieved 3 minutes after filling the box.

The mixture can have the following composition: 100 parts by weight of white silicon sand;
0.4 to 1.5 parts by weight of binder;
0.4 to 1.8 parts by weight of reactant; Catalyst (amine) in the gas state in the amount required for curing.

Of course, the invention is not limited to those described above Examples of execution are limited, since there are other types of execution and forms can operate without departing from the scope of the invention

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Claims (12)

- 9 - Claims 1. A process for the production of casting cores and molds, characterized in that a mixture of molding sand , binder and reactant is produced at low temperature and the mixture is kept under this condition of low temperature until it is introduced into the box and then this temperature influencing the mixture no longer applies. 2. The method according to claim 1, characterized in that rr.ar. the preparation of the mixture is carried out under a controlled atmosphere and the mixture under this condition of the controlled atmosphere until it is placed in the box and then omits the control of the atmosphere. 3. The method according to claim 1 or 2, characterized in that after introducing the mixture into the box Exposing the mixture to temperatures that are moderately above normal room temperatures. 4. The method according to claim 2 or 3, characterized in that the controlled atmosphere is a non-oxidizing atmosphere is. 5. The method according to any one of the preceding claims, characterized characterized in that the mixture is kept at a temperature below 5 ° C. during its preparation and storage. 6. The method according to any one of the preceding claims, characterized characterized in that synthetic resin-based agents, preferably phenoplasts, aminoplasts, polyesters, furan resins, be used. 309883/0464 -lo- BATH ORIGINAL 7. The method according to any one of the preceding claims, characterized in that the reactant is a hardening agent (Harder) is. 8. The method according to claim 7, characterized in that the hardening agent is a compound having an acidic function is. 9. The method according to any one of claims 1 - 8, characterized in, that the reactant is a catalyst. 10. The method according to claim 9, characterized in that the catalyst is an amine. 11. The method according to any one of claims 1-10, characterized in that that the reactant is a crosslinking agent, 12. Casting molds and casting cores, manufactured according to the method one of claims 1-11. 309883/0464