JP6408410B2 - Manufacturing method of molded body - Google Patents

Description

  The present invention relates to a method for producing a molded body.

  Conventionally, as one method for producing a molded body, “a first resin precursor (for example, a polyol) out of two types of resin precursors in which a crosslinking reaction is generated by mixing with an inorganic powder, a dispersion medium, and the like” A slurry obtained by mixing a slurry precursor containing a second resin precursor (for example, isocyanate) as a curing agent (gelling agent) of the two types of resin precursors is formed into a molding die. Widely known is a method for producing a molded body, including a “molding step of filling and molding in a space” and a “curing step of curing the slurry filled and molded in the molding space to obtain a molded body”. (For example, refer to Patent Document 1). Usually, this hardening process is performed under a normal pressure (atmospheric pressure).

WO 2004/035281

  In order to shorten the time required for the curing step in the above production method, the curing rate of the slurry (increase in the viscosity of the slurry) may be increased. In order to increase the curing rate of the slurry, for example, the volume concentration of the first and second resin precursors in the slurry is increased, or the volume concentration of the “catalyst promoting the crosslinking reaction” in the slurry is increased. That's fine.

  However, it has been found that when the curing step is performed under normal pressure, if the curing rate of the slurry is increased, cracks are likely to occur in the molded body during the curing step. The present inventor conducted research and experiments every day in order to deal with this problem. As a result, the present inventor has found an effective condition for making it difficult for cracks to occur in the molded body during the curing step.

  In view of the above, an object of the present invention is to provide a method for producing the above-described molded body, which is less prone to crack in the molded body during the curing step.

  The method for producing a molded body according to the present invention includes the same molding step as described above and the same curing step as described above. It is preferable that an isocyanate is used as the second resin precursor and a polyol is used as the first resin precursor.

The manufacturing method according to the present invention is characterized in that, in the curing step, the viscosity of the slurry at a shear rate of 0.01 (s ⁻¹ ) is from 1 × 10 ⁴ (mPa · s) to 1 × 10 ⁷ (mPa · s). ) Is set to Δt (s), and the viscosity of the slurry at a shear rate of 0.01 (s ⁻¹ ) is 1 × 10 ⁴ (mPa · s). F (Δt) ≦ P, where f (Δt) ≦ P, where P (MPa) is the pressure (pressurization pressure) for pressurizing the molding space over the period from 1 to 10 × 10 ⁷ (mPa · s). ) = (6.03 / Δt) −0.0123 (MPa) and Δt ≦ 450 (s).

  The inventor paid attention to pressurizing (from normal pressure) the molding space instead of maintaining the molding space at normal pressure (atmospheric pressure) in the curing step. Then, the present inventor has found that when the pressure is adjusted so that the above relationship is established, cracks are less likely to occur in the molded body during the curing process than when it is not (details will be described later). To do). More specifically, it has been found that the shorter the curing time Δt (the higher the curing rate), the greater the pressure applied to suppress the occurrence of cracks.

  In the manufacturing method according to the present invention, the volume concentration of the second resin precursor in the slurry at the time of mixing is 2 to 15% by volume, and the first resin precursor in the slurry at the time of mixing. The volume concentration is preferably 0.2 to 5% by volume, and the volume concentration of the dispersion medium in the slurry at the time of mixing is preferably 35 to 65% by volume.

  Moreover, when the said slurry contains the catalyst which accelerates | stimulates the said crosslinking reaction, it is preferable that the volume concentration of the said catalyst in the said slurry at the time of the mixing is 0.1-3 volume%.

It is the graph which showed an example of the relationship between elapsed time and the viscosity of a slurry in a hardening process. It is the graph which represented the result of Table 1 by the relationship between hardening time (DELTA) t and the pressurization pressure P. FIG.

  Hereinafter, the manufacturing method of the molded object which concerns on embodiment of this invention is demonstrated, referring drawings.

  In the manufacturing method according to the present embodiment, a molded body (a green molded body in a state before firing) is manufactured by the following procedure. This molded body can be fired later and used as a product.

<Applying release agent>
First, a fluorine-based mold release agent is used as a mold release agent on the inner wall of the molding space formed inside the mold used to mold the molded body (molding surface, inner surface of the concave portion where the slurry contacts). Apply one dispersed in an organic solvent. The application method can be appropriately selected from known methods. After application, the organic solvent is immediately volatilized, and as a result, the fluoric mold release agent is fixed to the molding surface. Thereby, at the time of mold release, the residue of a molded object becomes difficult to adhere and remain on the molding surface of a shaping | molding die. Therefore, damage to the surface of the molded body during mold release can be suppressed. In addition, even if a molded product residue adheres or remains on the molding surface of the mold, it can be easily removed.

<Slurry preparation>
Next, “a slurry precursor containing a first resin precursor out of two types of resin precursors that undergo a crosslinking reaction by mixing with an inorganic powder, a dispersion medium” and “two types of resin precursors” A second resin precursor as a curing agent among them is mixed to prepare a slurry. The slurry contains a dispersion aid and a catalyst as necessary.

  Examples of the slurry include 100 parts by weight of zirconia powder as inorganic powder, 27 parts by weight of a mixture of aliphatic polyvalent ester and polybasic acid ester as a dispersion medium, and ethylene glycol (polyol) 0 as the first resin precursor. .3 parts by weight, 5.3 parts by weight of 4,4′-diphenylmethane diisocyanate as a second resin precursor (curing agent, gelling agent), 3 parts by weight of a polycarboxylic acid copolymer as a dispersion aid, catalyst As a mixture, 0.05 part by weight of 6-dimethylamino-1-hexanol may be used.

  As inorganic powders, zirconium oxide, aluminum oxide, silicon oxide, nickel oxide, iron oxide, zinc oxide, manganese oxide, calcium oxide, tin oxide, silicon dioxide, yttrium oxide, cobalt oxide, copper oxide, lanthanum oxide, oxidation Metal compounds for forming ceramics having a desired composition by firing such as cerium, chromium oxide, titanium oxide, barium titanate, strontium titanate, nitrides such as silicon nitride, titanium nitride, aluminum nitride, Carbides such as silicon carbide and titanium carbide, powders made of nickel, palladium, platinum, gold, silver, copper, tungsten, molybdenum, and alloys thereof may be used. These inorganic powders may be used alone or in combination of two or more. As dispersion media, alcohols (methanol, ethanol, isopropyl alcohol, butanol, 2-ethylhexanol, etc.), ethers (2-methoxyethanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene ether, diethylene glycol) Monobutyl ether, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, etc.), esters (ethyl acetate, butyl acetate, dimethyl glutarate, triacetin, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol mono) Ethyl ether acetate, diethylene glycol monobutyl ether Acetate, propylene glycol monomethyl ether acetate), hydrocarbons (toluene, xylene, cyclohexane, etc.), N- methyl-2-pyrrolidone, N, N- dimethylformamide, organic solvents may be used, such as sulfolane. These dispersion media may be used individually by 1 type, or may be used in combination of 2 or more types. As the resin binder obtained by the crosslinking reaction, a phenol resin, a urethane resin, an acrylic resin, a polyester resin, a melamine resin, a urea resin, an alkyd resin, or the like may be used. That is, precursors such as phenol resin, urethane resin, acrylic resin, polyester resin, melamine resin, urea resin, and alkyd resin may be used as the first and second resin precursors. Polyurethane having polycarboxylic acid copolymer, sorbitan ester, polycarboxylate, polyglycerin fatty acid ester, phosphate ester salt copolymer, sulfonate copolymer, tertiary amine as dispersing aid Organic compounds such as polyester copolymers may be used. As the catalyst, amine compounds such as 6-dimethylamino-1-hexanol, triethylenediamine, and hexanediamine may be used.

  Examples of polyols that can be used for the first resin precursor include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, glycerin, trimethylolpropane, pentaerythritol, polyethylene glycol, poly Examples include tetramethylene ether glycol and polypropylene glycol.

  Examples of isocyanates that can be used for the second resin precursor include MDI (4,4′-diphenylmethane diisocyanate) isocyanate (resin), HDI (hexamethylene diisocyanate) isocyanate (resin), and TDI (tolylene diisocyanate). Examples thereof include isocyanate (resin), IPDI (isophorone diisocyanate) -based isocyanate (resin), isothiocyanate (resin), and modified products thereof.

<Molding process>
Next, in a state where the atmosphere surrounding the mold is maintained at room temperature and normal pressure (atmospheric pressure), the prepared slurry is injected and filled into the molding space of the mold from the inlet of the mold. This slurry injection is started immediately after the slurry is prepared. This is because the above-described crosslinking reaction (that is, curing of the slurry) is started immediately after the slurry is prepared.

<Curing process>
Next, the slurry filled and molded in the molding space is cured. In the curing step, the atmosphere surrounding the mold (and hence the molding space filled with the slurry) is maintained at room temperature while being pressurized (from atmospheric pressure). Hereinafter, the increase in pressure from the normal pressure is referred to as “pressurized pressure P”. The magnitude of the pressure P will be described later in detail.

FIG. 1 shows an example of the relationship between the elapsed time (min) from the completion of slurry filling and the viscosity (mPa · s) of the slurry at a shear rate of 0.01 (s ⁻¹ ) in the curing step. As can be understood from FIG. 1, generally, the viscosity of the slurry containing the resin binder obtained by the cross-linking reaction increases rapidly from less than 1 × 10 ⁴ to 1 × 10 ^7, and is 1 over a certain period thereafter. It is maintained in the vicinity of × 10 ⁷ and then gradually increases.

Hereinafter, the time required for the viscosity (mPa · s) of the slurry at a shear rate of 0.01 (s ⁻¹ ) to rise from 1 × 10 ⁴ to 1 × 10 ^{7 is referred} to as “curing time Δt (s)”. Define. The curing time Δt becomes shorter as the curing speed of the slurry (increase in the viscosity of the slurry) increases. In order to increase the curing rate of the slurry (thus shortening the curing time Δt), for example, the volume concentration of the first and second resin precursors in the slurry is increased, or “crosslinking reaction in the slurry is performed. The volume concentration of the “promoting catalyst” may be increased.

  In the curing step, the molding space is pressurized for at least the period of the curing time Δt. The pressurization of the molding space may be started before the start of the curing time Δt, or may be continued even after the end of the curing time Δt.

This curing process is continued until the slurry filled in the molding space is solidified. Here, “solidification” means that the shape of the molded body is maintained by the above-described crosslinking reaction or by volatilization of the dispersion medium. Specifically, for example, “solidification of slurry” refers to “a state where the viscosity (mPa · s) of the slurry is 5 × 10 ⁷ or more”. When this curing step is completed, the slurry is solidified in the molding space to form a molded body.

<Release>
Next, the mold is removed from the molded body formed in the molding space of the mold (mold release).

<Final drying>
Finally, the molded body after release is placed in an oven set at 100 ° C. and heated for 180 minutes. By this final drying process, the crosslinking reaction and the volatilization of the dispersion medium further progress, and the strength of the molded body is further increased. Thereby, handling of a molded object becomes easy. This final drying can be omitted. In the above, the manufacturing method of the molded object which concerns on embodiment of this invention was demonstrated.

(Pressurization in the curing process to prevent cracks)
As described above, in order to shorten the curing time Δt, the slurry curing rate may be increased. However, when the curing process is performed in a state where the molding space is maintained at normal pressure (atmospheric pressure), it has been found that if the curing rate of the slurry is increased, cracks are likely to occur in the molded body during the curing process.

  In order to cope with this problem, the present inventor paid attention to pressurizing the molding space (from normal pressure) instead of maintaining the molding space at normal pressure in the curing step. And this inventor discovered that the presence or absence of generation | occurrence | production of the crack of the molded object in a hardening process had a strong correlation with hardening time (DELTA) t and the pressurization pressure P. FIG. Hereinafter, a test for confirming this will be described.

(test)
In this test, a plurality of combinations of the components in the slurry, the first resin precursor in the slurry, the second resin precursor, the catalyst, and the volume concentration of each of the dispersion medium, the curing time Δt, and the pressure P are different. Examples were studied. Specifically, as shown in Table 1, 13 types of examples were examined. The number of samples in each example was 200. In each example, the shape of the molding space of the molding die (hence, the molded body) was a cylinder, and the size was 50 mm in diameter and 5 mm in height. The volume concentration of each component in the slurry is a value at the time of slurry preparation (during mixing).

In Table 1, as slurry A (Examples No. 1 to No. 5), inorganic powder, zirconium oxide (particle size 0.5 μm, specific surface area 7 m ² / g), fat as dispersion medium, fat 28.5 parts by weight of a mixture of an aromatic polyvalent ester and a dibasic acid ester, 1.3 parts by weight of ethylene glycol as a first resin precursor, and 4 parts as a second resin precursor (curing agent, gelling agent) , 4'-diphenylmethane diisocyanate, 7.8 parts by weight, 2.0 parts by weight of polymaleic acid copolymer as a dispersion aid, 0.93 parts by weight of 6-dimethylamino-1-hexanol as a catalyst What was used was used. As slurry B (Examples No. 6 to No. 10), 100 parts by weight of aluminum oxide (particle diameter 0.46 μm, specific surface area 4.3 m ² / g) as inorganic powder, and as a dispersion medium, 24.8 parts by weight of a mixture of a monovalent ester and a dibasic acid ester, 3.6 parts by weight of ethylene glycol as a first resin precursor, and 4,4 as a second resin precursor (curing agent, gelling agent) A mixture of 11.9 parts by weight of '-diphenylmethane diisocyanate, 2.0 parts by weight of polymaleic acid copolymer as a dispersion aid, and 1.7 parts by weight of 6-dimethylamino-1-hexanol as a catalyst. Was used. As slurry C (Examples No. 11 to No. 12), inorganic powder, zirconium oxide (particle size 0.5 μm, specific surface area 7 m ² / g), 100 parts by weight, dispersion medium, aliphatic polyvalent ester 41.5 parts by weight of a mixture of a dibasic acid ester and a dibasic acid ester, 0.13 parts by weight of ethylene glycol as a first resin precursor, and 4,4'- as a second resin precursor (curing agent, gelling agent) Used is a mixture of 1.43 parts by weight of diphenylmethane diisocyanate, 3.0 parts by weight of polymaleic acid copolymer as a dispersion aid, and 0.05 parts by weight of 6-dimethylamino-1-hexanol as a catalyst. It was done. As slurry D (Example No. 13), inorganic powder, zirconium oxide (particle size 0.5 μm, specific surface area 7 m ² / g), 100 parts by weight, dispersion medium, aliphatic polyvalent ester and dibasic acid 27 parts by weight of the ester mixture, 0.2 parts by weight of ethylene glycol as the first resin precursor, and 1.65 of 4,4′-diphenylmethane diisocyanate as the second resin precursor (curing agent, gelling agent) A mixture of 2.5 parts by weight of a polymaleic acid copolymer and 0.02 parts by weight of 6-dimethylamino-1-hexanol as a catalyst was used as a dispersion aid.

The curing time Δt is determined by the volume concentration of the first and second resin precursors in the slurry and the volume concentration of the catalyst. Therefore, as can be understood from Table 1, Δt is different among the slurry A, B, C, and D. The pressurization pressure P was adjusted by adjusting the pressurization from the normal pressure in the atmosphere surrounding the mold. In each example, the pressurizing pressure P was kept constant over at least the curing time Δt. For each example, the curing step was continued at room temperature until the slurry filled in the molding space solidified, that is, until the viscosity of the slurry was 5 × 10 ⁷ (mPa · s) or more. .

  In this test, it was confirmed whether or not cracks occurred in the molded product after the release after the curing step. This confirmation was made by visual observation as well as observation using a microscope. The results are as shown in the columns “Defect rate” and “Judgment” in Table 1. For each example, the “defective rate” is expressed as “(number of samples in which cracks occurred) / (total number of samples = 200)”. In the “judgment” column, “◯” indicates that the number of samples in which cracks occurred was zero, and “x” indicates that there was at least one sample in which cracks occurred. Show.

  FIG. 2 is a graph showing the results in the “determination” column of Table 1 in relation to the curing time Δt and the pressure P. In the graph shown in FIG. 2, f (Δt) is a curve that divides a region where a crack occurs and a region where a crack does not occur. Here, f (Δt) = (6.03 / Δt) −0.0123 (MPa). This formula was calculated using the least squares method.

  Note that Example 13 corresponds to “O” located on the rightmost side in the graph shown in FIG. In Example 13, although the determination is “◯”, since the pressurization pressure P = 0, the manufacturing method (P> 0) according to the present embodiment is not covered. Therefore, in the graph shown in FIG. 2, the longest value of the curing time Δt within the object of the manufacturing method (P> 0) according to the present embodiment is 450 (s).

  In this test, in Examples 1 to 12, the volume concentration of the first resin precursor is 0.2 to 5% by volume, the volume concentration of the second resin precursor is 2 to 15% by volume, and the volume concentration of the catalyst is 0.1. 1 to 3% by volume, and the volume concentration of the dispersion medium was in the range of 35 to 65% by volume.

  From the above, in the curing process, when the pressurization pressure P (> 0) is adjusted so that “f (Δt) ≦ P” is satisfied within the range of Δt ≦ 450 (s), compared with the case where it is not so. Thus, it can be said that cracks are hardly generated in the molded body. More specifically, it can be said that the shorter the curing time Δt (thus, the higher the curing rate), the greater the applied pressure P required to suppress the generation of cracks.

Claims (7)

A slurry precursor containing a first resin precursor of two types of resin precursors that undergoes a crosslinking reaction by mixing with an inorganic powder, a dispersion medium, and a curing agent of the two types of resin precursors. A molding step of filling the molding space of the molding die with the slurry obtained by mixing with the second resin precursor,
A curing step of obtaining a molded body by curing the slurry filled and molded in the molding space;
A method for producing a molded body, comprising:
In the curing step, the time required for the viscosity of the slurry to rise from 1 × 10 ⁴ (mPa · s) to 1 × 10 ⁷ (mPa · s) at a shear rate of 0.01 ( s ⁻¹ ) is Δt (S), and during the curing step, the viscosity of the slurry at a shear rate of 0.01 ( s ⁻¹ ) increases from 1 × 10 ⁴ (mPa · s) to 1 × 10 ⁷ (mPa · s). F (Δt) ≦ P, where f (Δt) = (6.03 / Δt), where P (MPa) is the pressure for pressurizing the molding space by pressurizing the atmosphere surrounding the mold. ) −0.0123 (MPa), Δt ≦ 450 (s) , 0.01 (MPa) ≦ P ≦ 0.15 (MPa) . In the manufacturing method of the molded object according to claim 1,
The manufacturing method of the molded object in which isocyanate was used as said 2nd resin precursor. In the manufacturing method of the molded object of Claim 1 or Claim 2,
The manufacturing method of the molded object in which the polyol was used as said 1st resin precursor. In the manufacturing method of the molded object according to any one of claims 1 to 3,
The manufacturing method of a molded object whose volume concentration of the said 2nd resin precursor in the said slurry at the time of the said mixing is 2-15 volume%. In the manufacturing method of the molded object according to any one of claims 1 to 4,
The manufacturing method of the molded object whose volume concentration of the said 1st resin precursor in the said slurry at the time of the said mixing is 0.2-5 volume%. In the manufacturing method of the molded object according to any one of claims 1 to 5,
The slurry includes a catalyst that promotes the crosslinking reaction,
The manufacturing method of the molded object whose volume concentration of the said catalyst in the said slurry at the time of the said mixing is 0.1-3 volume%. In the manufacturing method of the molded object according to any one of claims 1 to 6,
The manufacturing method of the molded object whose volume concentration of the said dispersion medium in the said slurry at the time of the said mixing is 35-65 volume%.

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