HU198140B - Powder composition suitable for producing liquid mould and core facing matters of aqueous medium - Google Patents

Abstract

The present invention is so-called. a powder composition suitable for the production of wet slurries used to protect the surface of foundry molds and cores. The powder composition comprises 90 to 95% by weight of filler, preferably zirconium silicate or alumina or graphite, 0.5 to 5% by weight film-forming material, preferably dextrin or carboxymethylcellulose sodium, with a viscosity of 0.1 to 1% by weight. modifying agent, preferably polysaccharide, 1 to 5% by weight suspension stabilizer, preferably mineral bentonite powder, and 0.02 to 0.6% by weight activating agent. As an activating agent, 0.01 to 0.3% by weight of a water-soluble alkali metal salt, preferably sodium carbonate or potassium carbonate, or sodium phosphate, and 0.01 to 0.3% by weight of a water-soluble magnesium salt, preferably magnesium chloride or magnesium sulfate, or 0.01 to 0.3% by weight of magnesium oxide. -1-

Description

FIELD OF THE INVENTION The present invention relates to a powder composition suitable for the production of aqueous liquid liquid foundry mold and core coating materials.

The powder composition comprises a finely ground filler, a film-forming agent, a viscosity modifier, a suspension stabilizer, and an activating agent.

In industrial practice, powdered compositions, commonly referred to as "powder fescue", are added to water to form liquid dies for coating the surfaces of molds and cores used in the casting of iron, steel and non-ferrous metals. The purpose of the coating is to make the coating of the wet beds harden the surface of the molds and cores on the one hand, and thus the sinter. eliminate spillage and prevent the molding material from burning on the casting surface and thus allow the formation of a clean casting material ·

The powder compositions should conveniently contain all of the components which, when suspended in water, provide good coating properties of the aqueous lozenges.

In addition, it is required that the wet bed: - does not sediment during storage, or if slightly sedimented, the sediment is loose and easy to mix;

- be easy to apply by sauce, brush, spray or other means;

- do not run on a vertical surface during application and during application;

- to form a perfectly smooth coating on the surface of the mold or core, and of uniform and desired thickness.

Only those wet beds which have high suspension stability and at the same time have beneficial rheological properties can satisfy the above requirements. Therefore, worldwide, there is extensive research in the field of powder formulations that can be used to provide these desirable properties for aqueous lozenges.

According to Baier, J. (GlESSEREI 59, 5-14-115 (1972)), mineral bentonite is used as a suspension stabilizing agent in aqueous fecals, especially sodium bentonite, which is also mined in some places.

Aqueous bedding made with mineral bentonite is generally advantageous for coating surfaces of molds and cores due to their high suspension stability, but has the disadvantage that their stability is not accompanied by favorable rheological properties. Another disadvantage is that the coatings made with them are prone to cracking.

It is an object of the present invention to provide a powder composition which can be formulated with a water-based suspension having a high stability and at the same time advantageous rheological properties in a suspension in water and thereby providing a non-cracking coating.

The present invention is based on the discovery that when a powder mixture containing a finely ground filler, film-forming agent, viscosity modifier and suspension stabilizer is added in a specific ratio of 2 activating agents, the powder composition can be formulated with aqueous lenses having the desired stability and properties.

In our research we found that alone. the use of activating agents ensures that the two most important rheological requirements are met: the lowest possible plastic viscosity and the highest possible Bingham yield strength.

It is known that measures to increase the yield point simultaneously increase the plastic viscosity, which is disadvantageous for wet beds.

In contrast, it has been found that with small amounts of activating agents, the Bingham yield strength can be increased without simultaneously increasing the plastic viscosity.

FIELD OF THE INVENTION The present invention relates to a powder composition for the production of aqueous media, liquid foundry molds and core coatings (so-called aqueous bedding) comprising a finely divided filler, film-forming agent, viscosity modifier, suspension stabilizer and 0.02 to 3.6% by weight of activator. contains material.

The filler may be any refractory tin or carbonaceous ground, preferably zirconium silicate, alumina alumina or graphite, which is a crystalline form of carbon in the hexagonal system.

As the film-forming agent, any water-soluble macromolecular material, preferably carboxymethylcellulose sodium, hydroxyethylcellulose or dextrin, which is an acid, enzyme or thermal decomposition product of starch, may be used.

A water soluble polysaccharide produced by Xantomonas campestris, such as Rhodopol 23, commercially available from Rh.one-Po ulenc, may be used as a viscosity modifier.

The suspension stabilizing agent used is a water-wettable rocky aggregate containing any clay mineral, preferably mineral bentonite, of which montmorillonite is the major clay mineral.

The activating agent may be a water-soluble alkali metal salt, preferably sodium carbonate, sodium phosphate or potassium carbonate, and a water-soluble magnesium salt, preferably magnesium chloride or magnesium sulfate, and magnesium oxide.

In preparing the powder composition, the finely ground air-dry components are added in any order to an effective powder mixer and then homogenized by vigorous stirring.

The most important advantages of the powder composition according to the invention are as follows:

I. Contains only water-soluble or water-soluble components,

2. when suspended in water, it forms a slurry which does not settle at all or only slowly and does not form a hard sediment which is difficult to mix at the bottom of the container.

3. the aqueous bed made of it has beneficial rheological properties,

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4. the coating obtained by the use of an aqueous slurry of powder mixture does not crack.

The powder composition of the present invention is illustrated by the following examples, which are not limited to the claims.

The weighed materials are stirred until they form a homogeneous powder composition.

This powder composition can be formulated with an aqueous slurry as described in Example 1 and dry-dried.

Example 1

The following components are weighed in any order into a Lódige powder mixer with a capacity of 2001:

94.03 parts by weight of eucon grits 1.00 parts by weight of dextrin 0.20 parts by weight of polysaccharide

4.50 parts by weight of natural bcntonite powder 0.18 parts by weight of sodium carbonate 0.09 parts by weight of magnesium oxide

The weighed materials are stirred until a homogeneous powder composition is formed.

100 g of the powder composition are suspended in vigorous stirring in 60 g of water and allowed to stand for one hour. The aqueous slurry thus prepared is applied to the mold or core by dipping, brushing or spraying and dried by drying or drying.

Example 2

The following components are weighed into a Lödige powder mixer with a capacity of 2001:

92.05 parts by weight of graphite powder

4.50 parts by weight of dextrin 0.30 parts by weight of carboxymethylcellulose sodium 3.00 parts by weight of natural bentonite 0.12 parts by weight of sodium carbonate 0.03 parts by weight of magnesium oxide

The weighed materials are stirred until they form a homogeneous powder composition.

100 g of the powder composition are suspended in 100 g of water with vigorous stirring and allowed to stand for one hour. The aqueous slurry thus prepared is applied to the surface of the fprina or seed by dipping, dipping or spraying and dried by drying or drying.

Example 3

The following components are weighed into a Lödige powder mixer with a capacity of 2001:

94.02 parts by weight of eucon grits 1.00 parts by weight of dextrin 0.20 parts by weight of polysaccharide

4.50 parts by weight of natural bcntonite powder 0.20 parts by weight of sodium phosphate 0.08 parts by weight of magnesium chloride

Example 4

The following components are weighed into a Lödige 200l powder mixer in any order:

92.01 parts by weight of graphite sheet

4.50 parts dextrin 0.25 parts polysacchard 3.00 parts natural bcntonite powder 0.15 parts sodium phosphate 0.09 parts magnesium sulfate

The weighed materials are stirred until they form a homogeneous powder composition.

From this polycarbonate, an aqueous slurry can be prepared as described in Example 2, and a dry coating is applied thereto.

Example 5

The following components are weighed into the Lödige 2001 powder mixer in any order:

94.00 parts by weight of eucon grits 1.00 parts by weight of dextrin 0.20 parts by weight of polysaccharide

4.50 parts by weight of natural beutylite milliliter 0.25 parts by weight of potassium carbonate 0.05 parts by weight of magnesium oxide

The weighed materials are stirred until they form a homogeneous powder composition.

This powder composition can be used to form an aqueous slurry on the mats described in Example 1 and dry dry them.

Example 6

Comparative suspension stability studies were performed to confirm the benefits of the powder composition of the invention.

The invention Γ. A powder composition was prepared which did not contain an activating agent (sodium carbonate and magnesium oxide) but zirconium alkali, bentonite powder, dextrin and polysaccharide.

Each powder composition was weighed four times (100 g) and suspended in water (60 g) with vigorous stirring.

Aqueous bed suspensions were poured into a 30 cm long and 3 cm diameter glass slide. The settling tubes were then sealed with a rubber stopper and placed in a vertical position,

198,140, and the bed suspensions were allowed to settle for 12, 24, 36 and 48 hours.

We then examined the number of times the settling tube had to be rotated 180 ° to resuspend the sediment. 5

The experimental results are shown in Table I.

Table 1

---.-- 10

Rotations required for resuspension Seating times ----------- Time i. The aqueous Fekecs activating agent containing a nonaqueous Fekecs Example ¹⁵

12 1 3 24 1 7 36 2 17 48 5 41

The experimental results clearly show that an aqueous slurry of powder composition containing the activating agent (0.18 parts by weight of sodium carbonate and 0.09 parts by weight of magnesium oxide) forms a much easier resuspendable sediment than the comparator sample.

Example 7

The aqueous activator compound prepared according to Example 6 and the non-activator comparator prepared in water were tested on a RHEDTEST-2 35 rotary viscometer at 20 ° C. A rogram of the two samples was determined. followed by Bingham's yield point and its plastic viscosity.

The results of the experiments are shown in Figs. Table 40 to 40 glazes.

II. spreadsheet

rheological parameter An aqueous bed of Example 1 is used An aqueous bed containing no activating agent Bingham's yield strength, 28 less than 1 Pa Plastic { ' b viscosity, 10 less than 5! inPa s

It is apparent from the data in the table that the aqueous bed prepared from the powder composition of Example 1 of TaMany preferably has a Bingham yield of about 30% compared to the comparative sample, while its plastic viscosity does not exceed the very preferred 10 mPa.s.

Claims (1)

Patent Claim Point A powder composition for aqueous liquid foundry molds and cores comprising 90-95% by weight of a finely divided filler, preferably zirconium silicate or alumina or graphite, 0.5-5% by weight of film-forming material, preferably dextrin or carboxylic acid. methylcellulose sodium, and 0.1 to 1% by weight of a viscosity modifier, preferably polysacliaride and i-5% by weight of a suspension stabilizer, preferably a mineral bentonite powder and an activating agent, characterized in that 0.01-0% as an activating agent. 3% by weight of a water-soluble alkali metal salt, preferably sodium carbonate or potassium carbonate or sodium phosphate, and 0.01-0.3% by weight of a water-soluble nickel salt, preferably magnesium chloride or magnesium sulfate, or 0.01-0, Contains 3% by weight of magnesium oxide.