KR101212874B1 - A Mold and A Mold Manufacturing Method - Google Patents

Abstract

The present invention relates to a mold and a method for producing a mold, the method for producing a mold, the first step of mixing the application powder, the silicate precursor and the metal alkoxide, the second step of compressing the mixture into a molded body, and the molded body A third step of drying; And, it may be characterized in that it comprises a fourth step of heat-treating the dried molded body.

Description

Mold and A Mold Manufacturing Method

The present invention relates to a mold and a method for producing a mold, and more particularly, to an environmentally friendly mold and a mold manufacturing method having a shorter mold making process and a high strength by improving the existing mold making process.

Current molds are molded by a convert mold process with low sintering temperature (about 1000 ° C), high mechanical and thermal properties, dimensional stability, and relatively short process times, especially in the automotive, building materials and aerospace industries. It is used to manufacture refractory castings for precision casting. The convert mold process is divided into the following six main processes.

(1) Preparation of Starting Mold Coated with Organic Binder (Resin)

(2) heat treatment at the mold of (1) at 200 ° C

(3) immersion in precursor mixture containing inorganic binder

(4) primary mold drying of the above (3)

(5) secondary mold drying of the above (4)

(6) heat treatment at the mold (1000) of the above (5)

The convert mold process undergoes hydrolysis and substitution during the process.

(1) hydrolysis reaction

NaOR + H ₂ O → ROH + NaOH

nSi (OR) ₄  +4 nH ₂ O → nSiO ₂  + 4 nROH

NaOR, ROH, NaOH, Si (OR) ₄ and SiO ₂ in the reaction Are named sodium alkoxides, alcohols, sodium hydroxide, alkyl silicates, silicates, respectively, and the sodium alkoxide used is one selected from alkali metal alkoxides. Sodium alkoxides and alkyl silicates are hydrolyzed by water to sodium hydroxide, silicates, and alcohols. In particular, alkyl silicates are condensation reactions of silanol ( SiOH ) molecules produced by hydrolysis simultaneously with hydrolysis. The gel reaction produces silicates.

(2) substitution reaction

2NaOH + SiO ₂ → Na ₂ O? SiO2 + H2O

Sodium silicate is synthesized by the reaction of sodium hydroxide with silicate at a high temperature of about 1000 ° C. Sodium hydroxide used in the reaction was used as a network modifier to easily produce a glass phase. In addition, during the reaction, all of the organic binder coated on the starting aggregate surface consisting of silica sand and alumina is burned. Through this process, the organic binder is replaced with an inorganic binder to form a refractory mold that can be used at high physical properties and high temperature.

However, the above-described prior art has the following problems.

Due to the heat treatment step at 200 ° C., the second step, and the third immersion step, there is a problem in that the process lengthens and the production cost increases. In addition, the conventional convert mold process is a process of replacing the inorganic binder by the combustion of the organic binder coated on the surface of the starting powder, the loss of the inorganic binder coated on the organic binder during the combustion process reduces the substitution efficiency.

And, due to the use of the organic binder, there is a problem due to environmental pollution.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and to provide a mold of a dry method and a method of manufacturing the mold having a simple process.

Another object of the present invention is to provide a new mold and a method for producing a mold without using an organic binder.

According to a feature of the present invention for achieving the object as described above, the method of producing a mold of the present invention, the first step of mixing the starting powder, the silicate precursor and the metal alkoxide, and the second step of compressing the mixture into a molded body And, a third step of drying the molded body; And, it may be characterized in that it comprises a fourth step of heat-treating the dried molded body.

In addition, another embodiment of the method for producing a mold of the present invention, the first step of mixing the starting powder, the silicate precursor and the metal alkoxide, the second step of first drying the mixture, and the second compression of the mixture into a molded article A third step and a fourth step of second drying the molded body; And, it may be characterized in that it comprises a fifth step of heat-treating the dried molded body.

In the first step, a curable binder may be further included.

The silicate precursor may be characterized by including any one or more of a monomolecular silicate precursor and a polymer siloxane precursor.

The silicate precursor may be composed of any one or more of PDMS or TEOS.

The metal alkoxide may be characterized by the following chemical formula.

M-O-R (M: alkali metal, R: hydrogen, alkyl group)

The curable binder may be composed of a fat-soluble binder.

The curable binder may be composed of a water-soluble binder.

In the second step, the pressurization temperature of the molded body may be molded at all temperatures below the boiling point of the silicate precursor, the metal alkoxide or the binder.

In the third step, any one of a method of leaving the molded body in the air for a hydrolysis reaction or a method of mixing water may be further added.

In the fourth step, it may be characterized in that any one of the method of leaving the molded body in the air for the hydrolysis reaction or a method of mixing the water is further added.

In the third step, it may be characterized in that the hydrolysis reaction takes place during the drying.

In the fourth step, it may be characterized in that the hydrolysis reaction takes place during the drying.

The third step, it may be characterized in that for 0.5 to 2 hours to dry at 80 to 100 ℃.

The fourth step, it may be characterized in that for 0.5 to 2 hours to dry at 80 to 100 ℃.

The second step, it may be characterized in that for 0.5 to 1 hour to dry at 80 to 100 ℃.

And, in another embodiment of the present invention can be characterized in that the mold manufactured by the above-described method.

In the mold and the method for producing the mold according to the present invention has the following effects.

First, there is an economic effect such as a cost reduction by simplifying the manufacturing process of the mold by mixing the inorganic binder and the starting powder particles at a time by the above-described dry process.

Second, by using a mixture of silicate precursors that do not cause hydrolysis and condensation reactions that are not used in the conventional binder for the manufacture of the mold can be produced a molded article having a high mechanical properties by increasing the conversion to silicate.

Third, there is no eco-friendly effect due to the use of organic binder.

1 is a flow chart showing a first embodiment of the manufacturing process of the mold according to the present invention.
Figure 2 is a flow chart showing a second embodiment of the manufacturing process of the mold according to the present invention.
Figure 3 is a view showing the shape by the scanning electron microscope of the actual photograph and the mold cross-section of the molded article according to Preparation Examples 1 and 2 manufactured according to the first embodiment of FIG.
Figure 4 is a view showing the shape by the scanning electron microscope of the actual photograph and the mold fracture cross-section of the molded article according to Preparation Examples 3,4 prepared in accordance with the second embodiment of FIG.
5 is a graph showing the breaking strength after the heat treatment of Preparation Examples 1 to 4 of FIGS.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms “comprises” or “having” are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other It is to be understood that the present invention does not exclude the possibility of the presence or the addition of features, numbers, steps, operations, components, parts, or a combination thereof.

Hereinafter, the refractory mold and the manufacturing method of the mold according to the present invention will be described in detail.

The method for manufacturing a refractory mold according to the present invention has various embodiments, but the present application describes two exemplary embodiments, and examples of various manufacturing processes may be prepared based on the processes listed in the above-mentioned problem solving means. Can be.

The method for producing the refractory mold includes a first step of mixing starting powder particles, a silicate precursor and a metal alkoxide, a second step of compressing the mixture into a molded body, a third step of drying the molded body, and the drying It may be characterized by comprising a fourth step of heat-treating the molded body.

First, in order to manufacture the refractory mold by this invention, a silicate precursor is mixed. The silicate precursor is tetramethoxysilane, tetraethoxysilane, tetra propoxysilane, tetra butoxysilane, tetraisopropoxysilane, methoxytriethoxysilane, dimethoxydiethoxysilane, ethoxytrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane, tetramethoxyethylsilane, tetrae Methoxymethylsilane, and the like, and polysiloxane compounds of the polymer form newly used in the present invention include diorganodichlorosilane, dimethyldichlorosilane, ethylmethyldichlorosilane, diethyldichlorosilane, di-n-propyldichlorosilane, and di-i. -Propyldichlorosilane, hexylmethyldichlorosilane, di-n-butyldichlorosilane, di-i-butyldichlorosilane, di-t-butyldichlorosilane and n-butylmethyldichlorosil Either one or a combination of, a linear hydroxy end-blocked polyorganosiloxane which is selected from the group consisting of. In addition, the terminal group includes one such as hydroxy, alkyl, vinyl, hydrogen, etc. Among them, a compound suitable for the required properties and properties can be selected and used, and the content is in the range of 1-40% by weight.

In particular, the silicate precursor in the present invention may be used alone or mixed with a specific weight ratio of the polysiloxane of the polymer form. In particular, the silicate precursor in the form of polysiloxane may be used by mixing precursors having different molecular structures such as viscosity and chain length.

Then, the silicate precursor and the metal alkoxide are mixed. The metal alkoxide is represented by the general formula MOR, M represents an alkali metal, R represents hydrogen or an alkyl group, specifically, methyl, ethyl, propyl, butyl, isopropyl, hexyl, cyclohexyl group Select from 1 to 60% by weight.

As a solvent for dissolving the two compounds, an alcohol solvent is generally used. For example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol, cyclohexyl alcohol, and the like are contained. Let it be by weight%.
In the conventional convert mold processor, the starting powder is mixed with an organic binder and formed into a starting base material, and then immersed in an inorganic binder to prepare a mold through heat treatment. In the present invention, the starting powder is mixed with an inorganic binder precursor to form and heat treated. Is to make a mold through. Therefore, it has a much more efficient and simple manufacturing process than the existing manufacturing process of immersing the mold. In addition, in the existing manufacturing process, the addition of an organic binder is essential to shape the starting powder, but in the present invention, the use of the organic binder is not essential by mixing the starting powder and the inorganic binder, which is environmentally friendly.
In order to produce a mold molded body, starting powder particles are first mixed with the silicate precursor, the metal alkoxide and the solvent mixture. The starting powder particles may be composed of various materials, for example, may be composed of beads of silica sand and aluminum oxide.

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After the second step of forming the mixture of the starting powder particles, the silicate precursor, and the metal alkoxide into the molded body by compression molding, a third step of drying the molded body is performed.

The pressurization temperature of the molded body in the second step may be molded at all temperatures below the boiling point of the silicate precursor, the metal alkoxide or the binder.

In addition, prior to the drying of the third step, in order to sufficiently hydrolyze the binder, a method such as a method of leaving the press-molded product in the air, a method of mixing water, or the like may be used. The inorganic binder used in the present invention is a binder in which gelation proceeds through a hydrolysis reaction. Therefore, in order to generate the reaction more effectively, the hydrolysis reaction occurring during drying may be further provided with a step such as a method of leaving it in the air or a method of mixing water.

Of course, the present invention is a step of drying the molded article containing the binder in a drier at 80-100 ℃ for about 0.5-2 hours to dry the alcohol mixed in the precursor or the alcohol produced during the hydrolysis reaction with the hydrolysis reaction of the binder It includes.

In the present invention, a separate process is not required for the hydrolysis reaction, thereby shortening the process time. In addition, the sol-gel reaction of the monomolecular silicate precursor produced during the drying process maintains the shape of the compact of the starting powder particles, thereby allowing the use of an organic binder, which is a basic material for the main mold of the existing starting powder particles. There is this.

The sol-gel reaction generated during the drying process is as follows.

NaOMe + H ₂ O ----> MeOH + NaOH

nSi (OEt) ₄ + 4nH ₂ O ----> (n + 1) SiO ₂ + 4nEtOH

In addition, the manufacturing process may further include a fourth step of heating the molded body. It is preferable to heat the said molded object at 1000 degreeC. At this time, a high-strength cast product is produced by the following vitrification reaction.

2NaOH + SiO ₂ ----> Na ₂ O? SiO ₂ + H ₂ O

In addition, the silicate precursor in the form of polysiloxane used in the above process is formed of silicate even without causing hydrolysis and condensation reaction, which is a reaction mechanism of the conventional convert mold process, and thus a high-strength cast product having a high conversion rate to a metal silicate after heat treatment. Can be produced.

Next, a second embodiment of the method for producing a refractory mold according to the present invention will be described.

The method for producing a refractory mold includes a first step of mixing starting powder particles, a silicate precursor, a metal alkoxide, and an organic binder, a second step of first drying the mixture, and a third step of compressing the mixture into a molded body. And a fourth step of secondly drying the molded body, and a fifth step of heat-treating the dried molded body.

First, in order to manufacture the refractory mold by this invention, a silicate precursor is mixed. The silicate precursor is tetramethoxysilane, tetraethoxysilane, tetra propoxysilane, tetra butoxysilane, tetraisopropoxysilane, methoxytriethoxysilane, dimethoxydiethoxysilane, ethoxytrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, tetramethoxymethylsilane. Tetramethoxyethylsilane, tetraethoxymethylsilane, and the like are used. As the polysiloxane compound of the polymer form newly used in the present invention, diorganodichlorosilane, dimethyldichlorosilane, ethylmethyldichlorosilane, diethyldichlorosilane, di-n -Propyl dichlorosilane, di-i-propyldichlorosilane, hexylmethyldichlorosilane, di-n-butyldichlorosilane, di-i-butyldichlorosilane, di-t-butyldichlorosilane and n-butylmethyldichlorosilane Any one or combination of linear hydroxy terminated polyorganosiloxanes selected from the group. In addition, the terminal group includes one such as hydroxy, alkyl, vinyl, hydrogen, etc. Among them, a compound suitable for the required properties and properties can be selected and used, and the content is in the range of 1-40% by weight.

In particular, in the present invention, the silicate precursor is used alone with the conventional silicate precursor and the polysiloxane of the polymer form listed above, or a mixture of the two compounds in a specific weight ratio. In addition, the polysiloxane silicate precursor may be used by mixing precursors having different molecular structures such as viscosity and chain length.

Then, the silicate precursor and the metal alkoxide are mixed. The metal alkoxide is represented by the general formula MOR, M represents an alkali metal, R represents hydrogen or an alkyl group, specifically, methyl, ethyl, propyl, butyl, isopropyl, hexyl, cyclohexyl group Select from 1 to 60% by weight.

As a solvent for dissolving the two compounds, an alcohol solvent is generally used. For example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, hexyl alcohol, cyclohexyl alcohol, and the like are contained. Let it be by weight%.

Then, starting powder particles are first mixed with the silicate precursor, the metal alkoxide and the solvent mixture in order to produce the molded body. The starting powder particles may be composed of various materials, for example, may be composed of silica sand and aluminum oxide.

The mixture of the starting powder particles, the silicate precursor and the metal alkoxide is dried at 80-100 ° C. for 0.5-1 hour. This is to dry water which is a solution of the water-soluble polymer in the curable binder. Therefore, depending on the type of the curable binder, that is, the case is not a water-soluble polymer, that is, in the case of a fat-soluble binder, the first drying step can be omitted.

Thereafter, a third step of forming the molded body by compression molding is performed. The pressurization temperature of the molded body in the second step may be molded at all temperatures below the boiling point of the silicate precursor, the metal alkoxide or the binder.

Thereafter, a fourth step of drying the molded body secondarily is performed.

Prior to the drying of the fourth step, in order to sufficiently hydrolyze the binder, a method such as a method in which the press-molded article is left in the air, a method of mixing water, or the like may be used.

Of course, in the present invention, the molded article containing the binder is dried in a drier at 80-100 ° C for about 0.5-2 hours to dry the alcohol mixed in the precursor or the alcohol produced during the hydrolysis reaction with the hydrolysis reaction of the binder. Process. Therefore, a separate process is not required for the hydrolysis reaction, which shortens the process time.

At this time, the hydrolysis reaction, ie, the following sol-gel reaction occurs during the drying process.

NaOMe + H ₂ O ----> MeOH + NaOH

nSi (OEt) ₄ + 4nH ₂ O ----> (n + 1) SiO ₂ + 4nEtOH

In addition, a manufacturing process is performed by further including a fifth step of heating the molded body, and the following vitrification reaction occurs.

2NaOH + SiO ₂ ----> Na ₂ O? SiO ₂ + H ₂ O

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

Preparation Example 1-4. Preparation of the binder

A new binder system was fabricated using the silicate precursors, metal alkoxides, alcohol compounds and curable binders shown in Table 1 below.

Manufacturing example
TEOS (wt% wt) PDMS (wt%) PVA (wt%) NaOMe (wt%) Isobutyl Alcohol (wt%) One 38 One - 56 6 2 30.4 7.6 - 56 6 3 29.4 7.6 One 56 6 4 - 37 One 56 6

TEOS: tetraethyl orthosilicate

PDMS: polydimethyl siloxane

PVA: Polyvinyl Alcohol

NaOMe: Sodium Methoxide

Alcohol: Isobutyl Alcohol

Production Examples 1 and 2 produce the production method of Example 1, and 3 and 4 are produced according to the production method of Example 2.

First, Preparation Examples 1 and 2 were mixed with tetraethyl orthosilicate (TEOS) or tetraethyl orthosilicate to polydimethyl siloxane (PDMS) as a silicate precursor and using a metal alkoxide compound sodium methoxide (MaOMe) in a weight ratio of 38:56 After mixing, add 6 wt% of isobutyl alcohol as a diluent and stir at room temperature for 0.5-1 hour. The starting powder is mixed and press-molded in this mixture, followed by drying at 80 ° C. for 1 hour and heat treatment at 1000 ° C. for 1 hour. Through this process, the inorganic binder coated on the surface of the starting powder is replaced with a glassy inorganic binder to produce a mold having high heat resistance and high strength.

In Preparation Examples 3 and 4, tetraethyl orthosilicate (TEOS) or tetradimethyl orthosilicate was mixed with polydimethyl siloxane (PDMS) in PV, which is a 1% curable binder, and used as a silicate precursor. Methoxide (MaOMe) is mixed in a weight ratio of 37:56, and 6 wt% of isobutyl alcohol is added as a diluent and stirred at room temperature for 0.5-1 hour. The starting powder is mixed with this mixture and dried at 80 DEG C for 1 hour. The starting powder mixture is then press-molded, dried at 80 ° C. for 2 hours, heat treated at 1000 ° C. for 1 hour. Through this process, the inorganic binder coated on the surface of the starting powder is replaced with a glassy inorganic binder to produce a mold having high heat resistance and high strength.

Figure 1 shows a view of Example 1 not using the organic binder according to the present invention. 2 is a view showing a manufacturing process according to the second embodiment.

According to these drawings, in comparison with the basic mold process, if a simpler process can lead to cost reduction and shortening of processing time, in particular, the manufacturing process of Example 1 can solve the environmental pollution problem by not using an organic binder.

3 and 4 are actual photographs of the molds manufactured by the manufacturing process of Examples 1 and 2 and the binders of Preparation Examples 1, 2, 3 and 4 (a-series before heat treatment and b-series after heat treatment) and The scanning electron microscope shape and elemental analysis at the fracture cross section are shown. According to the scanning electron microscope image, the bonding between the starting powder particles was observed due to the formation of the glass phase after the heat treatment, and the difference in the shape and elemental analysis of the mold according to the type and composition of the binder was not observed.

5 is a breakdown strength after heat treatment of the cast according to the process of the present invention of Examples 1 and 2. In the present invention, the strength of the binder and the mold manufactured by the manufacturing process is much higher than that of 0.58 MPa, which is the strength of the binder and the mold used in the conventional mold and commercial convert mold manufacturing process.

Claims (16)

A first step of mixing a starting powder, a silicate precursor, and a metal alkoxide;
A second step of compressing the mixture prepared in the first step into a shaped body;
A third step of drying the formed body produced in the second step; And,
And a fourth step of heat-treating the molded body dried in the third step. A first step of mixing the starting powder, the silicate precursor and the metal alkoxide;
A second step of first drying the mixture prepared in the first step;
A third step of compressing the mixture dried in the second step into a molded body;
A fourth step of secondly drying the formed article produced in the third step; And,
And a fifth step of heat-treating the molded body dried in the fourth step. 3. The method according to claim 1 or 2,
In the first step,
Method for producing a mold, characterized in that the curable binder further comprises. 3. The method according to claim 1 or 2,
The silicate precursor,
A method for producing a mold, comprising any one or more of a monomolecular silicate precursor and a polymer siloxane precursor. 3. The method according to claim 1 or 2,
The silicate precursor,
Method for producing a mold, characterized in that composed of any one or more of PDMS or TEOS. 3. The method according to claim 1 or 2,
The metal alkoxide,
Method for producing a mold, characterized in that the following formula.
MOR (M: alkali metal, R: hydrogen, alkyl group) The method of claim 3,
The curable binder,
A method for producing a mold, comprising a fat-soluble binder. The method of claim 3,
The curable binder,
A method for producing a mold, comprising a water-soluble binder. The method of claim 1,
Before drying in the third step,
Method for producing a mold, characterized in that any one of the method of leaving the molded body in the air for a hydrolysis reaction or a method of mixing water is further added. The method of claim 2,
Before drying in the fourth step,
Method for producing a mold, characterized in that any one of the method of leaving the molded body in the air for a hydrolysis reaction or a method of mixing water is further added. The method of claim 1,
In the third step,
A method for producing a mold, characterized in that a hydrolysis reaction takes place during the drying. The method of claim 2,
In the fourth step,
A method for producing a mold, characterized in that a hydrolysis reaction takes place during the drying. The method of claim 1,
In the third step,
Method for producing a mold, characterized in that the drying at 80 to 100 ℃ 0.5 to 2 hours. The method of claim 2,
The fourth step,
Mold production method, characterized in that for drying at 80 to 100 ℃ 0.5 to 2 hours. The method of claim 2,
The second step comprises:
Method for producing a mold, characterized in that the drying for 0.5 to 1 hour at 80 to 100 ℃. A process for producing a mold, characterized in that the starting powder, the silicate precursor, and the metal alkoxide are mixed, molded and compressed by a dry process.

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