CH659998A5 - Silicyl metaphosphate and use thereof in foundry articles - Google Patents

Abstract

Silicyl metaphosphate of the formula (I) specified in Claim 1 is suitable as a binding silicate component for the manufacture or treatment of foundry articles, optionally either in a mixture with aggregate or as an impregnant. <IMAGE>

Description

659 998

PATENT CLAIMS 1. Silicyl metaphosphate of formula (I)

HO

OH

O

OH

Si -

O - P -

O - Si

OH

Ö

OH

(I)

in which n = 1,2, 3 or 4.

2. Preparation for the manufacture or treatment of articles for the foundry, characterized in that the preparation consists at least partially of silicon metaphosphate of the formula (I) according to claim 1.

3. A process for the preparation of a preparation for the production or treatment of articles for the foundry, characterized by reacting a mixture of (A) a glycol ether, (B) colloidal silica sol and (C) at least partially hydrolyzed organosilicate with (D) phosphoric acid, so that an at least partially from silicon metaphosphate of formula (I) according to claim 1 existing reaction product is formed.

4. Articles for the foundry based on at least one refractory aggregate and at least one silicate component, characterized in that the silicate component is a silicon metaphosphate of the formula (I) according to claim 1.

5. A process for producing articles for the foundry based on at least one refractory unit and at least one silicate component, by combining the same, characterized in that at least one silicon metaphosphate of the formula (I) according to claim 1 is used as the silicate component.

6. The method according to claim 3, characterized by

(a) Mixing 25-40% by weight glycol ether of the formula (CnH2n + 1) OCH2CH2OH, inder = 1, 2, 3 or 4, 45-55% by weight acidic colloidal silica sol, which is at least 30% by weight available Si02 contains, and 5-20 wt .-% of a hydrolyzed organic silicate, which contains at least 40 wt .-% available Si02 and is an ethyl polysilicate, ethylene glycol monoethyl ether silicate, propyl silicate or butyl silicate, and

(b) reacting 5-25% by weight phosphoric acid having a concentration of approximately 75-85% by weight with the mixture obtained in step (a).

7. Article for the foundry according to claim 4, characterized in that it has at least one surface area in which the refractory aggregate is present together with the silicon metaphosphate of the formula (I).

8. The method according to claim 5, characterized in that the article is formed from the refractory aggregate and the silicon metaphosphate of the formula (I) is either mixed with the refractory aggregate before molding or incorporated into a surface area of the article after molding.

9. The method according to claim 8, characterized in that the article is at least partially coated with a mixture of refractory aggregate and a hybrid silicate and subsequently impregnated with silicon metaphosphate of the formula (I).

10. The method according to claim 8, characterized in that at least one surface area of the article is coated with a hybrid silicate, and in that a mixture of 10-90% by weight of concentrated phosphoric acid and 10-90% by weight is applied to the surface thus treated. Alkanol, such as isopropanol, to form silicon metaphosphate (I).

4111705.3 961968.3 957715.3 682668.3 576652.3211560 and 2 842 445. Some of the preparations described are incorporated into the molding sand or another, crushed refractory molding material as a binder or used as an impregnation or for coating a mold made from such material. The above-described silicate-containing preparations contain various other components or percentage-defined compositions and are generally effective for the intended purpose. Furthermore, some of the methods described can avoid the need to thermoset the molds, i.e. in other words, air-curable or unfired molds can be obtained. According to some known methods, however, air-curable molds are obtained, the molded skin or surface of which has an insufficient resistance to certain conditions which are frequently encountered in foundries. For example, some known formulations do not provide molded skin that can withstand the intense heat and erosion caused by the movement of the hot, turbulent metal-20 poured into the mold cavity. Other known preparations lead to multi-part skin structures that tend to crack when heated. Other known preparations allow the undesired penetration of metal into the mold stand 25 or disadvantageous chemical reactions or the splitting or breaking up of the surface of the mold cavity.

The patent holder's CH-PS 652 053 describes preparations for the manufacture or treatment of articles for the foundry; these preparations offer various advantages and contain certain silicates, namely hydride silicate and / or silicon metaphosphate, together with the refractory aggregate, which is preferably chosen from zirconium, silicon dioxide, aluminum oxide silicates, graphite, molten silicon dioxide, aluminum oxide, chromite, fibrous aluminum. 35 oxide silicates and mixtures of such substances, typically with particle diameters in the range from 10 to 3000 micrometers.

The present patent relates to silicon metaphosphate as a new substance or as part of an at least partially consisting preparation for the manufacture or treatment of articles for the foundry, a method for producing a preparation containing the silicon metaphosphate, and articles for the foundry and a method for producing such article.

The new silicon metaphosphate has the formula (I)

45

HO

50

OH

I.

Si OH

O

II

P

It

0

- 0 -

OH

I.

Si OH

- O

(I)

For the treatment and manufacture of articles for the foundry, such as casting molds, various silicate-containing binder preparations are known and z. B. in U.S. Patents 4,113,499,

in which n = 1, 2, 3 or 4, and the preparation according to the invention for the manufacture or treatment of articles for the foundry consists at least partially of silicon meta-55 phosphate of the formula (I).

According to the invention, a preparation for the production or treatment of articles for the foundry can be produced by reacting a mixture of (A) a glycol ether, (B) colloidal silica sol and (C) at least 60 partially hydrolyzed organosilicate with (D) phosphoric acid, so that a reaction product consisting at least partially of silicon metaphosphate of the formula (I) is formed.

A preferred embodiment of this method comprises

65 (a) mixing 25-40% by weight glycol ether of the formula (CnH2n + i) OCH2CH2OH, in which n = 1, 2, 3 or 4, 45-55% by weight of acidic colloidal silica sol which contains at least 30 Wt .-% available Si02, and 5-20 wt .-% of a hydrolyzed

organic silicates which contains at least 40% by weight of available SiO 2 and is an ethyl polysilicate, ethylene glycol monoethyl ether silicate, propyl silicate or butyl silicate, and that

(b) reacting 5-25% by weight phosphoric acid having a concentration of approximately 75-85% by weight with the mixture obtained in step (a).

Articles according to the invention for the foundry based on at least one refractory aggregate and at least one silicate component contain a silicon metaphosphate of the formula (I) as the silicate component. The article according to the invention preferably has at least one surface area in which the refractory aggregate is present together with the silicon metaphosphate of the formula (I).

For the inventive production of articles for the foundry on the basis of at least one refractory aggregate and at least one silicate component, which is a silicon metaphosphate of the formula (I), the article can be molded from the refractory agregate and the silicon metaphosphate of the formula (I) either before molding mix with refractory aggregate or incorporate into a surface area of the article after shaping. It can also be worked so that the article at least in some areas with a mixture of refractory aggregate and silicate component, eg. B. a hybrid silicate according to CH-PS 652 053, coated and subsequently impregnated with silicon metaphosphate of the formula (I).

In general, the silicon metaphosphate of the formula (I) for the treatment and production of casting molds and other articles for the foundry can be used as a binder or impregnating agent alone and without the addition of a refractory aggregate. The silicon metaphosphate can also be the molding sand or another aggregate, i. H. crushed refractory material, when mixing the aggregate or molding sand during its preparation for compaction to be added to a mold. The silicon metaphosphate is expediently used in an amount which gives the desired consistency. A compacted form made with silicon metaphosphate as a binder shows a higher bond strength and fire resistance than the corresponding, not so treated article. Furthermore, the treated article shows various advantages, explained below, such as faster air drying, higher raw strength and resistance to temperatures above 1650 ° C.

The term "hybrid silicate" means a silicate as it is used according to CH-PS 652 053 and z. B. is made according to the information of US-PS 3 961968. The term “raw or wet strength” here means the degree of hardness that must be achieved for the foundry with a moist or non-hardened casting mold or another article to avoid cracking, crumbling or collapse of the fresh mold.

To prepare a coating preparation, a predetermined amount of silicon metaphosphate and one of the refractory aggregates mentioned above or a mixture of such aggregates can be mixed to form a slurry which is to be applied to the surface of the mold cavity of a mold or to the surface part of a similar article to be treated which is to be treated Foundry is suitable. The mixture may also contain a predetermined amount of an additive to increase wet strength, e.g. B. polyvinyl acetate, polyvinyl alcohol or clay. The mixture may also contain a surfactant in order to better wet the aggregates during the preparation of the coating preparation. Suitable surfactants are the usual sodium soaps of fatty acids, carboxymethylcellulose, sodium sulfates, sodium tripolyphosphates and synthetic detergents, such as "Victawet" from Stauffer Chemical Company, "Wetsit" from Nopco Chemical Company and "Lestoil" from Noxell Corporation. Suitable fatty acid surfactants include “Wetanol” from Clyco Chemical

659 998

cals, Inc., "Surfact" from Casting Supply House, New York, and "Westasep" from West Chemical Products Inc. Preferred synthetic surfactants are those with a straight chain and 10 or more C chain atoms.

The production and use of silicon metaphosphate according to the invention are explained with reference to the figure and the examples below.

The figure shows a casting mold as an example of an article for the foundry.

example 1

component

% By weight

(Approximation)

Sulfuric acid (37%)

0.25

Water (distilled, deionized)

0.99

colloidal silica sol (acidic)

49.05

Ethylene glycol monoethyl ether

30.01

Phosphoric acid (85%)

11.60

Ethyl silicate, type 40

8.10

In a water-cooled reaction chamber, 0.25% concentrated sulfuric acid (37%) was combined with 0.99% distilled and deionized water. While stirring, 22.50% glycol ether was added to the reaction chamber and then immediately 8.10% ethyl silicate, type 40 (available from Union Carbide Company) was added. The mixture was then stirred for 30 minutes at a temperature carefully maintained between 20 and 27 ° C. After 30 minutes, this mixture was kept at 20-27 ° C for 48 hours, after which 49.05% acidic colloidal silica sol was slowly introduced into the reaction chamber. The mixture was then stirred for a further 2 K and the temperature of the reaction mixture was kept at 20-27 ° C, when this reaction is almost complete, a mixture of 11.60% concentrated phosphoric acid and 7.51% glycol ether is introduced and the whole thing for 30 min implemented. The final product was allowed to cool to room temperature and stored until a coating formulation was made.

Example 2

Component weight%

(Approximation)

Hydrochloric acid (37%) 0.15

Ethyl silicate, type 40 27.42

colloidal silica sol (alkaline or acidic) 10.63

Isopropanol (anhydrous 41.83

Phosphoric acid (85%) 19.94

The preparation obtained from these components was worked up as follows: In a reaction vessel equipped with a cooling device, 0.15% concentrated hydrochloric acid (37%) was carefully mixed with 10.63% alkaline colloidal silica. While stirring, 20.92% isopropanol was fed into the reaction vessel and stirred for 10 minutes. A premix of 20.92% isopropanol and 19.94% phosphoric acid was then introduced into the reaction vessel and the contents were stirred for 30 minutes. The resulting mixture was then kept at a temperature between 20 and 27 ° C for 24 h. After 24 h, 27.42% ethyl silicate, type 40, was slowly fed into the reaction vessel, the temperature being between 20 and 27 ° C

3rd

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

659 998

was held. The contents of the reaction vessel were then thoroughly mixed for 1 hour, kept between 20 and 27 ° C. for 24 hours and then stored for use in the preparation of a coating preparation.

Example 3

component

% By weight

(Approximation)

fireproof aggregate

75-90

Polyvinyl acetate or polyvinyl alcohol

0.5

Silicate component

10-25

Surfactant

0.1

40.9% refractory aggregate were in a reaction vessel, which was provided with a cooling device in order to keep the reaction mixture below 30 ° C. at all times, with 18.5% hybrid silicate according to CH-PS 652 053 or silicon metaphosphate according to example 1 or 2 , mixed for 15 minutes, whereupon 0.5% polyvinyl acetate was fed into the reaction vessel. The resulting mixture was stirred for 5 minutes, whereupon 0.1% surfactant was added and mixing was continued for a further 5 minutes. The refractory aggregate was added to this preparation as the remaining portion and the aggregate mixture was worked through for 15 min. After thorough mixing, the product was allowed to cool to room temperature.

The coating preparation produced in this way is in the form of a slurry and can be applied in any suitable manner to a specific surface part of the casting mold of the core or similar article to be treated.

Example 4

In the drawing, as an example of an article for the foundry, a mold 10 in the form of a compact made of quartz sand 12 or other crushed refractory material, as is usually used for foundry technology, is shown in a molded bottle 14. If the article to be treated is a mold, at least the surface of the mold cavity 16 intended for receiving the molten metal and optionally all parts of the mold surrounding the mold cavity, as well as the mold inlet or sprue channel 18 and main channel 20 with the described preparation, e.g. by spreading, painting, spraying or other application methods. The thus coated mold is then allowed to air dry for about 20 minutes, whereby a mold is formed which has a skin or coating 22 with a thickness of approximately 0.4 to 0.8 mm in the surface parts treated in this way, and which with the Silicon metaphosphate is impregnated to a depth of about 5 cm to increase the bond strength of the mold. Casting molds treated in this way have an improved surface quality and show considerable resistance to the penetration of turbulent molten metal into the mold surface and to peeling and erosion. Furthermore, the casting mold treated in this way has a considerably higher fire resistance than the corresponding non-treated casting mold.

In a reactor vessel which contains a cooling device in order to keep the reaction mixture below 30 ° C. at any time, 40.9% refractory aggregate was added to 18.5% silicon metaphosphate with stirring and the whole was mixed for 15 minutes. Then stirring was stopped and 0.5% polyvinyl acetate was slowly introduced into the vessel. The resulting mixture was stirred for 5 minutes and 0.1% surfactant was added, and the mixture was stirred for a further 5 minutes. Then the remaining portion of the refractory aggregate was added to the preparation and the resulting mixture was mixed for 15 minutes. After thorough mixing of the product, it was allowed to cool to room temperature.

The coating preparation prepared in the manner just described and containing silicon metaphosphate is in the form of a slurry and can be applied in the same way to the surface or a part of the surface of the casting mold, core or similar articles to be treated for the foundry according to Example 4 described methods are applied. In general, the surface of the cavity and any other surrounding parts of the mold can be coated with the preparation of silicon metaphosphate and refractory aggregate either by spreading, brushing, spraying or by another application method. The thus treated mold or the core or another article for the foundry is then left to air dry for about 20 minutes. The articles obtained in this way show increased resistance to delamination, cracking, erosion and adverse heat effects; Impregnations with the silicon metaphosphate with an impregnation depth of about 5 cm give the shape or the article an increased bond strength. In general, the wet or raw strength of casting molds treated with silicon metaphosphate and other articles for the foundry is three times higher. When the molds treated in this way are heated, the strength of the mold increases over tenfold and proves to be resistant to temperatures of over 1650 ° C. without deformation due to high-temperature softening.

25th

35

40

Example 5

Component.

% By weight

(Approximation)

fireproof aggregate

75-90

Polyvinyl acetate or polyvinyl alcohol

0.5

Silicon metaphosphate

10-25

Surfactant

0.1

Example 6

The silicon metaphosphate obtained according to Examples 1 and 2 can also be used independently, i. H. In addition to or instead of the use in combination with an aggregate as a coating, it can also be used alone as an impregnating agent or impregnation which is to be applied to the surface of the casting mold, the core 43 or another article to be treated for the foundry. The silicon metaphosphate can be applied to the surface to be treated by the methods described above or in any other suitable manner. After application, the silicyl-50 metaphosphate generally influences the surface of the treated area or the mold cavity in two ways: on the one hand, the surface treated in this way is provided with a coating which has a skin or thickness of typically about 25 to 75 micrometers; in addition, the silicon metaphosphate 55 usually penetrates to a depth of about 5 cm below the surface treated in this way. The mold thus treated, or the core or similar articles for the foundry, after air drying for about 20 minutes, have properties similar to those of surfaces treated according to Example 4.

60 Generally advantageous when using silicon metaphosphate in the manner described is its inert behavior against molten steel. It inhibits any adverse chemical reactions between the components of the mold or other articles impregnated therewith and certain components in the molten metal, such as titanium and aluminum in molten steel, which could have an undesirable oxidizing effect. The silicon metaphosphate also generally improves the radiographic properties of the casting

Reduction in the amount of exfoliated molding material that would be embedded in the casting during casting.

Example 7

This example illustrates another method of applying a silicon metaphosphate impregnation to a mold, core, or other article for the foundry, resulting in the manufacture of articles that have all of the above properties of articles impregnated with silicon metaphosphate. This method is based on a two-step process in order to avoid possible disadvantages of a previously produced silicon metaphosphate impregnating agent which occur due to changes during storage. In this procedure, silicon metaphosphate is formed on the treated surface when hybrid silicate is applied according to CH-PS 652 053 to the surface to be treated, specifically from a mixture of highly concentrated phosphoric acid and alcohol, as indicated below:

5,659,998

component

% By weight

(Approximation)

Phosphoric acid (85%)

50-90

Ethanol or isopropanol (anhydrous)

10-50

The impregnation of the casting mold was carried out as follows: io The casting mold was first treated with a hybrid silicate preparation according to Example 3 (silicate component = hybrid silicate according to CH-PS 652 053) by brushing on, spraying on or by another suitable application method. After this treatment of the surface of the casting mold, the mixture of phosphoric acid and isopropanol was then applied in the same way to the mold surface and the mold was allowed to air dry for about 20 minutes, after which it was usable.

M

1 sheet of drawings