JP6913405B1 - Manufacturing method of molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization efficiency of a molding die when a product containing a non-metallic inorganic material is manufactured by using the molding die. The present invention comprises an injection step of mixing a raw material solution containing a powder, a solvent, a dispersant, and a curable resin made of a non-metallic inorganic material and a curing agent and injecting the curing agent into a molding die, and the raw material solution. An in-mold curing step of curing a mixture of the curing agents in the molding mold to form a primary cured product having a predetermined hardness, a demolding step of removing the primary cured product from the molding mold, and the molding. An out-of-mold curing step of obtaining a secondary cured product having a predetermined hardness by advancing the curing reaction of the primary cured product released from the mold, a drying step of drying the secondary cured product, and after drying. It is a method of manufacturing a molded product by sequentially executing a degreasing step of degreasing the secondary cured product and a sintering step of sintering the secondary cured product after degreasing, and the hardness of the primary cured product is increased. , 40% to 70% of the hardness of the secondary cured product obtained in the out-of-mold curing step, which is a method for producing a molded product. [Selection diagram] Fig. 1

Description

The present invention relates to a method for producing a molded product containing a non-metallic inorganic material such as silica glass or ceramics as a raw material.

An optical fiber used for an optical communication transmission path, a laser guide, etc. is composed of a core having a high refractive index and a clad layer having a low refractive index surrounding the core, and is a non-metal such as silica glass or fluoride glass. The main material is inorganic substances. With the progress of communication technology, in addition to general single-mode fiber, special structures such as multi-core fiber, pore-assisted fiber, photonic crystal fiber, and panda fiber (PANDA (Polarization-maintaining AND Absorption-reducing) fiber) Optical fiber is being developed.

An optical fiber having a special structure has a complicated manufacturing process of an optical fiber base material as compared with an optical fiber having a general structure, which requires labor and cost. For example, the pore-assisted fiber is manufactured as follows. First, a clad layer covering the core and its outer circumference is formed by the VAD method (Vapor phase Axial Deposition method) to obtain a first base material. Next, a plurality of through holes extending in the longitudinal direction of the base material are formed in the clad layer of the first base material by cutting with a drill or ultrasonic waves, and the second base material (first with through holes) is formed. Base material) is obtained. Then, the fiber base material is completed through the washing, dehydrating, and drying steps of the second base material. An optical fiber is completed by drawing the fiber base material thus obtained (Patent Document 1).

However, it is difficult to adjust the inner diameter, roundness, straightness, etc. of the through hole to a desired value by cutting with a drill or ultrasonic waves. In particular, in the case of a fiber base material having a small inner diameter dimension of the through hole and a large length dimension, it becomes difficult to adjust the roundness and straightness of the through hole with high accuracy.
Further, in the case of a fiber base material for a multi-core fiber, a step of inserting a core material manufactured in another process into the through hole of the second base material and welding it to the inner surface of the through hole is added to the above-mentioned manufacturing method. However, it is difficult to reduce the inner surface roughness of the through hole by cutting with a drill or ultrasonic waves. Therefore, the light loss (scattering loss, absorption loss, etc.) at the boundary between the core and the clad layer becomes large.

In order to solve the above problems, a method of manufacturing an optical fiber by molding has been proposed (Patent Document 2). In this method, a curing agent is mixed with a glass raw material solution consisting of silica glass powder, distilled water, a dispersant, and a curable resin, and the mixture is injected into a molding mold in which a metal rod for a core is arranged. Since the mixture is solidified by curing the curable resin in the mold, the mold and the metal rod for the core are separated from the solidified body. Then, the solidified body is dried and fired to complete the optical fiber base material.

Japanese Unexamined Patent Publication No. 2004-339004 Japanese Unexamined Patent Publication No. 2013-147384 Japanese Patent Application Laid-Open No. 2007-136912

In the method described in Patent Document 2, the roundness and straightness of the through hole can be increased by using a metal rod for a core having excellent roundness and straightness. Further, since the inner surface roughness of the through hole is determined by the outer surface roughness of the metal rod for the core, the inner surface of the through hole can be made smooth by mirror-polishing the outer surface of the rod. can. Compared to the case where a through hole is formed by cutting, it is easier to manufacture a metal rod for a core with excellent roundness and straightness, and to mirror-polish the outer surface of the metal rod for a core. Therefore, it is possible to reduce the labor and cost required for manufacturing the optical fiber base material.

By the way, at the manufacturing site of a molded product, the molding mold desorbed from the solidified body is used again for manufacturing the molded product after the dirt is removed from the surface thereof. Therefore, in the usage time of the molding die in the manufacturing process of the molded product, that is, in the manufacturing method described in Patent Document 2, from the injection of the glass raw material solution and the curing agent into the molding die to the removal of the molding die from the solidified body. If the time can be shortened, the utilization efficiency of the molding die can be improved.

The time required for the mixture of the glass raw material solution and the curing agent to solidify depends on the combination of the curable resin and the curing agent contained in the glass raw material solution and the conditions of the curing reaction. Therefore, although the solidification time can be shortened to some extent by appropriately setting the combination of the curable resin and the curing agent and the reaction conditions, there is a limit.

Although an optical fiber has been described as an example here, there is a similar problem when various products made of non-metallic inorganic materials such as silica glass and ceramics are manufactured by using a molding die.

An object to be solved by the present invention is to improve the utilization efficiency of a molding die when a product containing a non-metallic inorganic material is manufactured using the molding die.

The present invention made to solve the above problems
An injection step in which a raw material solution containing a powder, a solvent, a dispersant, and a curable resin made of a non-metallic inorganic material and a curing agent are mixed and injected into a molding die.
An in-mold curing step of curing a mixture of the raw material solution and the curing agent in the molding mold to form a primary cured product having a predetermined hardness.
A demolding step of desorbing the primary cured product from the molding die,
An out-of-mold curing step of obtaining a secondary cured product having a predetermined hardness by advancing the curing reaction of the primary cured product desorbed from the molding mold.
A drying step of drying the secondary cured product and
A degreasing process that degreases the secondary cured product after drying,
It is a method of manufacturing a molded product by sequentially executing a sintering step of sintering a secondary cured product after degreasing.
The out-mold curing step includes an in-liquid curing step in which the curing reaction proceeds in a state where the primary cured product is immersed in a liquid.
The hardness of the primary cured product is 40% to 70%, preferably 45% to 65% of the hardness of the secondary cured product obtained in the extramold curing step.

In the above method, the "hardness" is typically a durometer hardness, but indentation hardness such as barcol hardness or monotron hardness can be used. It is also possible to express "hardness" by physical quantities that can be converted into durometer hardness, barcol hardness, monotron hardness, and the like. Examples of such physical quantities include elastic deformation rates such as Young's modulus.

The "predetermined hardness" of the primary cured product means the hardness that allows the primary cured product to be removed from the molding die. The "predetermined hardness" of the secondary cured product generally refers to the hardness when the curing reaction is completed, but there is a problem (for example, cracking) in the drying step, the degreasing step, and the sintering step. If cracks do not occur, the hardness may be such that the curing reaction is not completely completed.

In the method for producing a molded product according to the present invention, the hardness of the primary cured product obtained by curing the mixture of the raw material solution and the curing agent in the molding mold is after the primary cured product is desorbed from the molding mold. The hardness of the secondary cured product obtained by advancing the curing reaction of the primary cured product in the out-mold curing step was adjusted to 40% to 70%, preferably 45% to 65%. In other words, the mold is detached from the cured product (primary cured product) before the curing reaction between the curable resin and the curing agent in the mold is completed, and the remaining curing reaction is performed outside the mold. I made it. Therefore, since the usage time of the molding die can be shortened, the utilization efficiency of the molding die can be improved.

The process drawing of the manufacturing method of the molded article which concerns on this invention. The graph which shows the relationship between the forming time and the durometer hardness. The graph which shows the change of hardness in each process.

The present invention comprises an injection step of mixing a raw material solution containing a powder, a solvent, a dispersant, and a curable resin made of a non-metallic inorganic material and a curing agent and injecting the curing agent into a mold, and the raw material solution and the curing agent. An in-mold curing step of curing the mixture in the mold to form a primary cured product having a predetermined hardness, a demolding step of desorbing the primary cured product from the mold, and desorption from the mold. An out-of-mold curing step of obtaining a secondary cured product having a predetermined hardness by advancing the curing reaction of the primary cured product, a drying step of drying the secondary cured product, and a secondary cured product after drying. This is a method of manufacturing a molded product by sequentially executing a degreasing step of degreasing and a sintering step of sintering a secondary cured product after degreasing, in which the hardness of the primary cured product is outside the mold. This is a method for producing a molded product, which is 40% to 70% of the hardness of the secondary cured product obtained in the curing step.

Here, examples of the non-metallic inorganic material include silica (SiO ₂ ) glass, calcium fluoride (CaF ₂ ) glass, and ceramics. Examples of ceramics include aluminum oxide, zirconium oxide, silicon nitride, silicon carbide, and aluminum nitride. The powder made of a non-metallic inorganic material may be composed of a single material, or may be a mixture of a plurality of types of materials. Further, the raw material solution may contain metal impurities.

The curable resin refers to a resin that forms a three-dimensional network structure by a polymerization reaction, and is preferably liquid. Examples of the curable resin include epoxy resin, melamine resin, phenol resin, acrylic acid resin, urethane resin and the like.
As the curing agent, for example, an amine-based curing agent, an acid anhydride-based curing agent, a polyamide-based curing agent, or the like can be used, but it is preferable to use an appropriate curing agent in combination with a curable resin.

In the method for producing a molded product according to the present invention, a cured product (primary cured product) having a hardness at a predetermined value is removed from the molding mold before the curing reaction of the mixture of the raw material solution and the curing agent is completely cured. Let go. Whether or not the hardness of the primary cured product is at a predetermined value can be determined from the elapsed time by examining in advance the relationship between the elapsed time after mixing the raw material solution and the curing agent and the hardness of the mixture. Can be done.

In the above manufacturing method, the primary cured product, which is in a state before the curable resin is completely cured, that is, has a low hardness and is relatively soft, is desorbed from the molding die. If the shape of the primary cured product cannot be maintained after being separated from the mold, the original purpose will be deviated. Therefore, the primary when the primary cured product is separated from the mold so as not to cause such a problem. The hardness of the cured product is set.

In the production method of the present invention, after the primary cured product is removed from the molding die, an out-of-mold curing step for advancing the curing reaction of the primary cured product is performed. The out-of-mold curing step is carried out until the curing reaction of the curable resin is almost completed. The state in which the curing reaction is almost completed means a state in which the hardness of the secondary cured product hardly changes even if the out-of-mold curing process is continued. In the present invention, assuming that the hardness of the secondary cured product is 100%, the hardness of the primary cured product is 40 to 70%, preferably 45 to 65%.

Whether or not the curing reaction of the secondary cured product is almost completed depends on the time elapsed from the desorption of the primary cured product from the molding die or the time elapsed since the start of the out-of-mold curing process. By investigating the relationship with the hardness of the cured product (primary cured product) in advance, it can be determined from the elapsed time.

The out-of-mold curing step may be performed at room temperature or in a heating atmosphere. It is preferable to carry out the out-of-mold curing step in a heating atmosphere in that the progress of the curing reaction can be accelerated. Further, the curing reaction may be allowed to proceed first at room temperature and then further proceeded in a heating atmosphere. The temperature of the heating atmosphere may be set to an appropriate value depending on the combination of the curable resin and the curing agent contained in the raw material solution, the blending ratio of the curable resin and the curing agent, and the like.

Further, the out-of-mold curing step is preferably performed in a state where the primary cured product is immersed in a liquid. In particular, in the case of heating, by immersing the primary cured product in a liquid, it is possible to alleviate a rapid temperature rise of the primary cured product and prevent rapid drying in the next drying step. Therefore, it is possible to prevent defects such as cracks and cracks in the manufactured molded product and deformation of the molded product.

The liquid for immersing the primary cured product is usually the same as the solvent contained in the mixture, but different types of liquids can be used as long as they have the same properties as the solvent contained in the mixture. Typically, the liquid is water, but alcohols, organic solvents and the like can be used depending on the type of non-metallic inorganic material, the use of the molded product, and the like.

In Patent Document 3, a mixture containing a ceramic powder, a dispersant, a curable resin, and a solvent is injected into a molding mold, and a curing agent is put therein to cure the cured product, and the cured product is removed from the molding mold. A method is disclosed in which the cured product is immersed in a solvent, heat-treated, dried, degreased, and sintered to produce a ceramic molded product. In this method, the cured product is heated between the demolding step and the drying step, and at first glance, it is similar to the manufacturing method according to the present invention. However, in the method of Patent Document 3, the molding die is desorbed from the cured product in a sufficiently cured state, and the curing reaction of the cured product hardly proceeds in the heat treatment between the demolding step and the drying step. Further, the heating step between the demolding step and the drying step in the method of Patent Document 3 aims to suppress cracking of the cured product during drying, and is different from the out-mold curing step in the present invention.

Next, an embodiment in which the present invention is applied to a method for producing a glass molded product will be described. FIG. 1 shows an example of a method for manufacturing a glass molded product. _{In this example, first, silica (SiO 2} ) glass powder, distilled water, a dispersant, and a curable resin, which are the materials of the raw material solution, are put into a ball mill and mixed (S1). As a result, a raw material solution in which each material is finely pulverized and uniformly mixed is obtained.

Next, the raw material solution is taken out from the ball mill, a mixture of this and a curing agent is injected into a molding die (S2), and the mixture is cured by a self-curing reaction in the molding die (in-mold curing reaction) to obtain a primary cured product. (S3). The primary cured product is in a state before it is completely cured and has a predetermined hardness. The hardness of the primary cured product will be described later.
Subsequently, the primary cured product is removed from the molding die (S4). Then, the curing reaction (out-of-mold curing reaction) of the primary cured product is allowed to proceed at room temperature and / and in a heated atmosphere (S5). The out-of-mold curing reaction is carried out in a state where the primary cured product is immersed in a liquid and / or left in a gas (air). As a result, a secondary cured product in a state in which the curing reaction is substantially completed can be obtained.
Further, the molded product is completed by drying (S6), degreasing (S7), and sintering (S8) the secondary cured product.

In the present embodiment, the primary cured product in a state before the mixture of the raw material solution and the curing agent is completely cured is removed from the molding die. Therefore, the usage time of the molding die used to obtain one molded body can be shortened, and the utilization efficiency of the molding die can be improved.

Hereinafter, examples will be specifically described.
[Example 1]
The raw material solutions of the formulations shown in Table 1 were placed in a ball mill and mixed for 24 hours. Then, after taking out the mixture from the ball mill, the mixture and the curing agent (see Table 1) were injected into a molding mold and left at 20 ° C. for 45 minutes, 55 minutes, 180 minutes, 360 minutes and 1050 minutes. Then, the mixture cured in the molding die (hereinafter, cured product) was removed from the molding die.

In order to examine the hardness of the cured product and the leaving time (the elapsed time after mixing the raw material solution and the curing agent, that is, the curing time), the durometer hardness of the cured product immediately after being removed from the molding die was measured. A durometer (GS-719G, A type) manufactured by TECLOCK Co., Ltd. was used for measuring the durometer hardness. Table 2 shows the relationship between the curing time and the durometer hardness of the cured product. The durometer hardness shown in Table 2 is the average value of the durometer hardness of the three cured products prepared for each curing time. Further, with regard to the curing time of 360 minutes, three cured products were prepared in two steps.

Next, the cured product after desorbing the molding die was immersed in distilled water and left at room temperature for 18 hours (standing at room temperature), then the distilled water was heated to 55 ° C. and left for another 2 hours (heating at 55 ° C.). )did. The step of leaving at room temperature and 55 ° C. for a total of 20 hours is also referred to as a "in-liquid curing step". After the in-liquid curing step, the cured product was taken out from distilled water, left to stand in an atmosphere of 60 ° C. for 48 hours (hereinafter referred to as "in-gas curing step"), and then dried at 120 ° C. for 48 hours (hereinafter referred to as "" "Drying process"). The out-of-mold curing step of the present invention is composed of the in-liquid curing step and the in-gas curing step. Further, the step of leaving in distilled water at room temperature and the step of leaving in distilled water at 55 ° C. correspond to the first step and the second step of the present invention, respectively.

The durometer hardness of the cured product after being left at room temperature in the in-liquid curing step, after heating at 55 ° C., after the in-gas curing step, and after the drying step was measured. Among these measurement results, Table 3 shows the durometer hardness after demolding of the cured product having a curing time of 55 minutes and after each subsequent step, and after demolding of the cured product having a curing time of 360 minutes and thereafter. Table 4 shows the durometer hardness after each step as a representative. As can be seen from these results, there was a large difference in hardness after demolding between the cured products having a curing time of 55 minutes and 360 minutes, but the hardness and gas after in-liquid curing (55 ° C.) There was no significant difference in hardness after medium curing (60 ° C.).

[Example 2]
Example 2 is substantially the same as Example 1 except that the particle size of the silica glass powder contained in the raw material solution is different from that of Example 1. That is, the raw material solution of the formulation shown in Table 5 was put into a ball mill, a mixture was prepared under the same procedure and the same conditions as in Example 1, and this mixture and the curing agent shown in Table 5 were injected into a molding die. After injecting the mixture and the curing agent into the mold, the mixture was left at 20 ° C. for 55 minutes, 65 minutes, 70 minutes, 180 minutes, 360 minutes and 1050 minutes. Then, the mixture cured in the molding die (hereinafter, cured product) was removed from the molding die to obtain a cured product. Next, as in Example 1, an out-of-mold curing step (in-liquid curing step (normal temperature, 55 ° C.), in-gas curing step (60 ° C.)) was applied to the cured product after the molding die was removed. , The drying step was carried out in order.

Similar to Example 1, the durometer hardness of the cured product immediately after being removed from the mold, after being left at room temperature in the in-liquid curing step, after heating at 55 ° C., after the in-gas curing step, and after the drying step. It was measured. The results are shown in Tables 6 to 8. Table 6 shows the relationship between the curing time and the durometer hardness of the cured product immediately after being removed from the mold. Table 7 shows the durometer hardness of the cured product having a curing time of 70 minutes after demolding and after each subsequent step, and Table 8 shows the durometer hardness of the cured product having a curing time of 360 minutes after demolding and after that. The durometer hardness after each step is shown. As can be seen from Tables 6 to 8, the same results as in Example 1 were obtained in Example 2.

FIG. 2 is a graph showing the relationship between the durometer hardness of the cured product immediately after demolding and the curing time in Examples 1 and 2. The horizontal axis of the graph represents the curing time, and the vertical axis represents the durometer hardness. Further, the triangular mark (Δ) represents the result of Example 1, and the circle mark (◯) represents the result of Example 2. As can be seen from this graph, when the curing time exceeded 360 minutes, the durometer hardness of the cured product was almost constant regardless of the length. Therefore, in Example 1 and Example 2, the mixture was contained in 360 minutes. It was found that the curing reaction of the curable resin was almost completed. Further, at this time, since distilled water was discharged from the cured product and the curing was contracted, the cured product could be easily removed from the molding die.

On the other hand, when the curing time was 180 minutes to 360 minutes, although the curing had progressed considerably, the shrinkage rate was small, so that cracks occurred when the cured product was separated from the molding die.

On the other hand, it was found that when the curing time was in the range of 40 minutes to 180 minutes, the cured product could be desorbed from the mold without being deformed or cracked. When the curing time is in the range of 40 minutes to 180 minutes, water is not discharged from the cured product and therefore the cured product is not shrunk, so that the cured product is in a state of being fixed to the inner surface of the molding die. However, since the hardness of the cured product was small at this point, the cured product was not cracked even if the cured product was peeled off from the inner surface of the mold when the molding mold was removed.
On the other hand, when the curing time was shorter than 40 minutes, the cured product was stretched and deformed when it was removed from the molding die, and the shape of the cured product could not be maintained.

Further, as is clear from FIG. 2, no significant difference was observed between the curing time and the durometer hardness between Example 1 and Example 2. From this, it was presumed that the particle size of the silica glass powder contained in the raw material solution had a small effect on the hardness of the cured product.

FIG. 3 is a graph showing the results shown in Tables 3, 4, 7, and 8. The vertical axis of the graph represents the durometer hardness. Further, in FIG. 3, the polygonal line indicated by the triangular mark (Δ) is demolded when the curing time is 55 minutes (Example 1) and 70 minutes (Example 2), that is, the curing reaction is not sufficiently advanced. The result of the cured product is shown. Further, the polygonal lines indicated by circles (◯) indicate the results of the cured product that was demolded with a curing time of 360 minutes (Examples 1 and 2), that is, the cured product was demolded in a state where the curing reaction was almost completed.

As can be seen from FIG. 3, the value of the durometer hardness immediately after the demolding of the cured product that was demolded when the curing reaction was not sufficiently advanced is immediately after the demolding of the cured product that was demolded when the curing reaction was almost completed. Although it was about half of the value of the durometer hardness in the above, the durometer hardness of both became almost the same when the submerged curing step (normal temperature) was completed. Then, by the submerged curing step (55 ° C.), the curing reaction of both progressed further and the durometer hardness increased, and the durometer hardness of both at the time when the drying step was completed was the same. Further, since the same results were obtained in both Example 1 and Example 2, it was presumed that the particle size of the silica glass powder contained in the raw material solution had a small effect on the curing reaction after demolding.

[Example 3]
The raw material solutions of the formulations shown in Table 9 were placed in a ball mill to prepare a mixture under the same procedure and conditions as in Example 1, and this mixture and the curing agent shown in Table 9 were injected into a molding die. This is cured under the conditions shown in Table 10 below, then demolded, and sintered through an extramold curing step (in-liquid curing (normal temperature), in-liquid curing (55 ° C.)), a drying step, and a degreasing step. A quartz glass capillary having a diameter of 2 mm and a length of 5 mm was produced. As a result, a good silica glass molded product was obtained without cracking in the cured product in any of the drying step, the degreasing step, and the sintering step.

[Example 4]
The raw material solutions of the formulations shown in Table 11 were placed in a ball mill to prepare a mixture under the same procedure and conditions as in Example 3, and the mixture and the curing agent shown in Table 11 were injected into a molding die. This is cured under the conditions shown in Table 12 below, then demolded, and sintered through an extramold curing step (in-liquid curing (normal temperature), in-liquid curing (55 ° C.)), a drying step, and a degreasing step. A ceramic capillary having a diameter of 2 mm and a length of 5 mm was produced. As a result, a good ceramic molded product was obtained without cracking in the cured product in any of the drying step, the degreasing step, and the sintering step.

Claims (5)

An injection step in which a raw material solution containing a powder, a solvent, a dispersant, and a curable resin made of a non-metallic inorganic material and a curing agent are mixed and injected into a molding die.
An in-mold curing step of curing a mixture of the raw material solution and the curing agent in the molding mold to form a primary cured product having a predetermined hardness.
A demolding step of desorbing the primary cured product from the molding die,
An out-of-mold curing step of obtaining a secondary cured product having a predetermined hardness by advancing the curing reaction of the primary cured product desorbed from the molding mold.
A drying step of drying the secondary cured product and
A degreasing process that degreases the secondary cured product after drying,
It is a method of manufacturing a molded product by sequentially executing a sintering step of sintering a secondary cured product after degreasing.
The out-mold curing step includes an in-liquid curing step in which the curing reaction proceeds in a state where the primary cured product is immersed in a liquid.
A method for producing a molded product, wherein the hardness of the primary cured product is 40% to 70% of the hardness of the secondary cured product obtained in the extramold curing step. The method for producing a molded product according to claim 1, wherein the non-metallic inorganic material is silica glass. The method for producing a molded product according to claim 1, wherein the non-metallic inorganic material is ceramics. The invention according to any one of claims 1 to 3, wherein in the in-liquid curing step, a first step of proceeding the curing reaction in a liquid at room temperature and a second step of proceeding the curing reaction in a heated liquid are performed in order. Mold manufacturing method. The out-of-mold curing step is a step performed after the in-liquid curing step, and the cured product taken out from the liquid is heated to a higher temperature than the liquid in the in-liquid curing step and from a temperature in the drying step. The method for producing a molded product according to any one of claims 1 to 4, further comprising a curing step in gas in which the curing reaction is allowed to proceed by leaving the material in a low-temperature gas.

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