DD212444A1 - FORMAL SEALANT FOR ALUMINUM DIE CASTING - Google Patents

Abstract

The subject of the invention is a mold release agent for aluminum diecasting based on aqueous compounds containing phosphorus compounds. The invention goal is, via a novel mold release agent a wesentl. To increase the service life of the molds. It is the object of the invention to develop a mold release agent for aluminum diecasting with improved wetting of the mold surface and at the same time an antioxidant and anticorrosive action. The mold release agent is wesentl. characterized by a content of a salt of Dithiophosphorsaeure u. an alkylamine as an effective composition, an alkyl ether sulfate or ethoxylated alkylphenol as an emulsifier u. on a polyol as a release agent.

Description

Mold release agent for die-cast aluminum

Field of application of the invention

The invention relates to a mold release agent for aluminum die casting based on phosphorus compounds containing aqueous emulsion.

Characteristic of the known technical solutions

In metal die casting, liquid metal is forced into a mostly two-part mold in which the melt solidifies. The casting must be easy to remove after opening the mold without damaging its surface or mold. This can only be achieved by applying a mold release agent to the mold before the molten metal is pressed into the mold. Such a mold release agent has a number of requirements. Thus, even when applied in a small layer thickness, a high separation effect must be ensured. No deposits should form on the surface of the mold or casting. The release agent must completely and evenly wet the surface of the mold and also reach hard to reach parts. The release agent should not cause corrosion either on the fitting or on the mold, but should provide a protective effect in addition to the release force. Furthermore, the release agent should be composed so that when applied to the warm form or in contact with the liquid metal no dangerous, harmful or annoying vapors arise.

It is extremely difficult to meet all the requirements mentioned at the same time. Often, the improvement of one property leads to the deterioration of another, so mold release agents are often used only for certain technologies or metal alloys.

It is known that in aluminum die casting with paste-like mold release agents based on waxes good demolition can be achieved (DD-PS 19615). The disadvantage here is the polluting and harmful to health of the resulting at the casting temperature between 640 ⁰ C and 75O ⁰ C decomposition product. In addition, because of the high viscosity of these pasty agents, a manual application to the mold is required, which precludes automation of the die casting process.

For use in high-pressure die casting machines, liquid mold release agents are required which, owing to their low viscosity, can be sprayed and thus can be applied quickly and uniformly to the mold. As such release agents, e.g. known solid or pasty compositions, dissolved in organic solvents (hydrocarbon fractions, such as gasoline, kerosene or kerosene, etc.) used (see, for example, DE-AS 2,107,103). In their application, however, there is an increased risk of fire or a significant health risk by in the. Room air discharged components or their decomposition products.

As further liquid release agents, aqueous emulsions of solvent-active mixtures are increasingly used. They contain as active components u.a. Hydrocarbons, salts and esters of carboxylic acids, substituted phenolates, polysaccharides, mono- and polyamines, sodium silicates, phosphoric acid and phosphorous acid esters, alkoxyalkylsilanes, graphite and talc.

For example, in DE-OS 2,604,710 describes the use of an aqueous emulsion 'of mixtures of esters of pentaerythritol and a monocarboxylic acid with a nonionic emulsifier and small amounts of phosphoric acid as a mold release agent.

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From DE-AS 1 558 115, the use of an aqueous size of a polystyrene emulsion, polyethylene, a secondary alkyl sulfonate, carboxymethyl cellulose and sodium O-phenylphenalate, optionally with the addition of graphite, as a mold release agent for aluminum die casting known. However, the aqueous release agent emulsions used hitherto have the disadvantage that when they are applied, the casting molds are subjected to greater stress, for example due to low lubrication of the ejection substances, and corrosion problems, inter alia, also occur in the storage of the molds. The corrosion protection requires additional treatment of the mold surfaces. So will. For example, in DE-AS 2,242,837 claimed the preparation of a corrosion protection by iodination, subsequent introduction of elemental sulfur with an organic solvent and subsequent heat treatment. Another method is based on the treatment of the mold in a salt bath of 90 % borax and 10 % zirconia at 950 ⁰ C (DE-AS 2 010 323).

Object of the invention

The aim of the invention is to achieve over a novel mold release agent for aluminum diecasting based on phosphorus compounds containing aqueous emulsions, using commercially available components, a substantial increase in service life of the molds, compared to the previously applied. -Th aqueous release agents.

The technical problem which is solved by the invention

The invention has for its object to develop a mold release agent for aluminum die casting based on phosphorus compounds containing aqueous emulsion with respect to the previously applied aqueous release agents, improved wetting of the mold surface and at the same time to develop antioxydant and anticorrosive effect.

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Features of the invention

There was found a mold release agent for aluminum die casting based on phosphorus compounds containing aqueous emulsion. The mold release agent is characterized by a content

between 0.5 and 1.5% by mass of a salt of dithiophosphoric acid of the general formula

' ^X ' _rn +

wherein R. and R _{0 are} identical or different alkoxy radicals - \ d

with 4 to 12 carbon atoms or the bivalent

Radical -NH-CO-NH-CO-NH- and M ^{n +} denote a zinc, magnesium, aluminum or alkylammonium ion, and

between 0.5 and 1.0% by weight of an alkylamine of the general formula R 1 -NH _O , in which R represents an alkyl radical having 12 to 24 carbon atoms, as an effective composition,

- between 0.05 and 0.2 mass%

an alkyl ether sulfate or ethoxylated alkylphenol as emulsifier,

- between 0.5 and 5.0% by mass

a polyol, preferably a sugar, a methylcellulose, glycerol or a water-soluble starch, as a release agent.

The mold release agent according to the invention may additionally contain between 2.0 and 5.0% by weight of graphite.

It is particularly advantageous to start from release agent concentrates, for example as can be seen from the following exemplary embodiments, which in the case of the user with water or

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aqueous polyol solutions are diluted. This reduces in particular the transport effort from the manufacturer to the user. The release agent concentrates are storage stable.

By means of the mold release agent according to the invention are good to very good demolitions at error-free surface of the castings and at the same time significantly longer service life of the molds, due to the antioxidant and anticorrosive effect of the mold release agent achieved.

embodiments

The invention will be explained in more detail by the following embodiments, but the invention is not limited to these examples.

The mold release agent was tested on die casting dimensions of aluminum alloys, with the emulsions being applied to the hot molds automatically or by hand. The surface of the castings was light yellowish to brownish without error and only at high levels of polyol. It was assumed that release agent concentrates, which are diluted with water or aqueous polyol solutions.

Concentrate A

100 g of zinc di-ethylhexyl dithiophosphate 100 g of fatty amine C ₂₀

20 g emulsifier MF

30 g graphite 750 ml water

Concentrate B

100 g zinc dinonyl dithiophosphate 100 g fatty amine C ₅₀ 20 g emulsifier MF 780 ml water

59 a3 y

Folyole

1. sugar (10% aqueous solution)

2. Methylcellulose (10% aqueous solution)

3. Glycerol

4. starch, soluble (5% aqueous solution)

Below are some proven separation solutions:

Release agent I

100 ml of concentrate A

50 ml of methylcellulose (10% aqueous solution) 850 ml of water

Release agent II

50 ml of concentrate A

50 ml of methylcellulose (10% aqueous solution) 900 ml of water

Release agent III

100 ml concentrate A, 50 ml glycerol 850 ml water

Release agent IV

100 ml of concentrate B 100 ml of sugar (10% aqueous solution) 800 ml of water

Claims (2)

J Λ Κ Μ Λ * "W w * t Sri ^"1 indungs of entitlement 1. mold release agent for aluminum die casting based on phosphorus compounds containing aqueous emulsion, characterized by a content
- between 0.5 and 1.5% by mass a salt of dithiophosphoric acid of the general formula wherein R. and Rp denote identical or different alkoxy radicals having 4 to 12 carbon atoms or the bivalent radical -NH-CO-NH-CO-NH- and M ^{n +} a zinc, magnesium, aluminum or alkylammonium ion,
and between 0.5 and 1.0 mass% an alkylarain of the general formula R 1 -NEL, in which R 1 denotes an alkyl radical having 12 to 24 carbon atoms, as an active composition, - between 0.05 and 0.2 mass% an alkyl ether sulfate or ethoxylated alkyiphenol as emulsifier, - between 0.5 and 5.0% by mass a polyol, preferably a sugar, a methylcellulose, glycerol or a water-soluble starch, as a release agent. 2. mold release agent according to item 1, characterized by an additional content of graphite between 2.0 and 5.0% by mass.