JP7097115B2 - Manufacturing method of glass sintered body - Google Patents

Description

The present invention relates to a method for producing a glass sintered body having through holes, and more particularly to a method for producing a glass sintered body as an optical fiber preform.

An optical fiber is composed of a core having a high refractive index and a clad layer having a low refractive index surrounding the core. The core and clad layer of the optical fiber are mainly made of non-metal inorganic substances such as quartz glass (silica glass) and fluoride glass. Conventionally, a general optical fiber for communication is a single-mode fiber having one core as a signal transmission path, but as the transmission capacity in an optical communication system increases, a plurality of cores are provided in one optical fiber. Multi-core fiber with has been developed.

An optical fiber is manufactured by spinning (drawing) an optical fiber preform (optical fiber base material). There is a perforation method as a general method for producing a preform. The hole opening method is a method in which a hole is made in a quartz rod using a drill, a core rod is inserted into the hole, and then spinning is performed. The hole-drilling method makes it difficult to make holes with high dimensional accuracy in a large preform, and it is troublesome especially in the case of a multi-core fiber.

On the other hand, there is a method called a slurry casting (slurry casting) method (Patent Document 1). In the slurry casting method, a curing agent is mixed with a glass raw material solution containing quartz glass powder, a solvent, a dispersant, and a curable resin to form a slurry, and this slurry is injected into a molding die in which a metal rod for a core is arranged. And cure. After curing, it is demolded and the metal rod is detached. The core rod is inserted into the hole formed by the detachment of the metal rod, and dried, degreased, and sintered to further remove the solvent and the curable resin contained in the molded product to produce a preform. In this method, by appropriately setting the shape, size, and position of the metal rod to be placed in the molding die, it is possible to obtain an optical fiber preform having a core with high dimensional accuracy in the clad layer.

Japanese Unexamined Patent Publication No. 2014-094884

In the slurry casting method, the molded body taken out from the molding die shrinks in the process of reaching the preform which is a glass sintered body, and the dimensions change. When the molded body is large, the absolute value of the dimensional change amount becomes large, so that the molded body is liable to crack or deform, and it is difficult to maintain the dimensional accuracy.
Although the preform of the optical fiber for optical communication has been described here, there is a similar problem when the preform for a fiber laser or other optical fiber is manufactured by the slurry casting method.

An object to be solved by the present invention is to prevent cracks from easily occurring in a molded body or a glass sintered body obtained in a process of manufacturing a glass sintered body by a slurry casting method.

The first aspect of the present invention made to solve the above problems is
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
On the cross section perpendicular to the central axis of the glass sintered body having the through hole, the maximum virtual circle having the largest diameter among the virtual circles inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole is The inner diameter of the molding die and the diameter of the hole forming rod are set so as to have a diameter of 14 mm or more and 58 mm or less, and the hole forming rod is arranged.

In addition, the second aspect of the present invention made to solve the above problems is
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
The glass sintered body has a plurality of through holes, and the glass sintered body has a plurality of through holes.
When the virtual circle circumscribing the outer periphery of the through hole is defined as the second virtual circle in the region surrounded by the plurality of through holes on the cross section perpendicular to the central axis of the glass sintered body, the second virtual circle is defined. The inner diameter of the molding die and the diameter of the hole-forming rod are set so that the diameter of the virtual circle is 14 mm or more and 58 mm or less, and the hole-forming rod is arranged.

Furthermore, the third aspect of the present invention made to solve the above problems is.
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the glass sintered body has one through hole, a virtual circle inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole on a cross section perpendicular to the central axis of the glass sintered body. Of these, the diameter of the virtual circle with the largest diameter is 2a, the outer diameter of the glass sintered body is 2R, the number of through holes is n, the diameter of the through holes is 2r, and the closest contact portion between the through holes. _Bth defined by the following formula (1) when the interval is 2S and the weight part of the curable resin is C when the amount of the quartz glass powder contained in the slurry is 100 parts by weight. Each step is performed so that the value is 73.5 or less.
B _th = {aC ² ( ^{R2 -} nr2) / (R + nr)} / 1000 ... (1)
(However, R ≧ 15, C ≧ 7.5. A, R, r, S are values when the unit is expressed in mm.)

Further, the fourth aspect of the present invention made to solve the above problems is.
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the glass sintered body has a plurality of through holes, among the virtual circles inscribed in the outer periphery of the glass sintered body and circumscribed in the through holes in the cross section perpendicular to the central axis of the glass sintered body. Of the virtual circle having the maximum diameter and the virtual circle circumscribing the outer periphery of the through hole in the region surrounded by the plurality of through holes on the cross section perpendicular to the central axis of the glass sintered body. The diameter of the virtual circle with a large diameter is 2a, the outer diameter of the glass sintered body is 2R, the number of through holes is n, the diameter of the through holes is 2r, and the distance between the closest portions between the through holes is 2S. When the amount of the quartz glass powder contained in the slurry is 100 parts by weight and the weight part of the curable resin is C, the _Bth value defined by the following formula (1) is 73. Each step is performed so as to be 5 or less.
B _th = {aC ² ( ^{R2 -} nr2) / (R + nr)} / 1000 ... (1)
(However, R ≧ 15, C ≧ 7.5. A, R, r, S are values when the unit is expressed in mm.)

Furthermore, the fifth aspect of the present invention made to solve the above problems is.
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the accommodating portion of a mold having a tubular accommodating portion in which a pore-forming rod is arranged, and the curable resin is cured. Process and
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces.
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
On the cross section perpendicular to the central axis of the glass sintered body having the through hole, the maximum virtual circle having the largest diameter among the virtual circles inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole is The shape of the molding die and the shape of the hole-forming rod are set so as to have a diameter of 14 mm or more and 58 mm or less, and the hole-forming rod is arranged.

According to the method for manufacturing a glass sintered body according to the present invention, it is possible to suppress the occurrence of cracks in the molded body or the glass sintered body in the step of manufacturing the glass sintered body.

The figure which shows the manufacturing process of the glass sintered body which concerns on this invention. The figure for demonstrating the virtual circle of the molded body which has one through hole. The figure for demonstrating the virtual circle of the molded body which has two through holes. The figure for demonstrating the virtual circle of the molded body which has 4 through holes. The figure for demonstrating the virtual circle of the molded body which has 5 through holes. The figure for demonstrating the virtual circle of the molded body which has 7 through holes. Figures (a) to (c) show cross sections of the molded bodies of Samples 4 to 6 of Production Example 2.

The first aspect of the present invention is
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
On the cross section perpendicular to the central axis of the glass sintered body having the through hole, the maximum virtual circle having the largest diameter among the virtual circles inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole is The inner diameter of the molding die and the diameter of the hole forming rod are set so as to have a diameter of 14 mm or more and 58 mm or less, and the hole forming rod is arranged.

In the slurry casting method, the slurry is placed in a molding die and solidified, and then the molding die and the hole-forming rod are separated from the solidified body to obtain a molded body. The molded product thus obtained becomes a glass sintered body through a drying step, a degreasing step, and a sintering step. In the drying step, the solvent contained in the slurry is mainly removed from the molded product. In the degreasing step, the curable resin contained in the slurry is mainly removed from the molded product.

In the drying step, it takes longer for the internal solvent to be discharged to the outside of the molded product than the solvent near the surface of the molded product. If the dry state of the surface and the inside of the molded body are different for a long time, cracks occur in the molded body during the drying process. Further, in the degreasing step, the curable resin inside the molded product is difficult to be removed from the molded product. If the curable resin contained in the molded body is not sufficiently removed and remains inside the molded body, the molded body may be cracked during the degreasing step or the sintered body may be cracked during the sintering step.

In the case of a molded body having a through hole, the solvent and the curable resin contained in the molded body are discharged from the outer peripheral surface of the molded body and the inner peripheral surface of the through hole. Therefore, in the present invention, a maximum virtual circle is defined as an index for facilitating the discharge of the solvent and the curable resin, and the inner diameter of the molding mold is set so that the maximum virtual circle has a predetermined size (diameter). The diameter (outer diameter) of the hole forming rod was set, and the hole forming rod was arranged. The maximum virtual circle is defined on the cross section of the glass sintered body as the final product obtained by the manufacturing method of the present invention. Therefore, the inner diameter of the molding die and the diameter (outer diameter) of the hole forming rod are set in consideration of the shrinkage of the molded body caused by the drying, degreasing, and sintering steps, and the hole forming rod is arranged. It will be. With such a configuration, in the present invention, the solvent, the curable resin, and the dispersant contained in the molded product can be efficiently removed in the drying step and the degreasing step.

Further, the second aspect of the present invention is
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
The step of sintering the degreased molded product and the glass sintered body have a plurality of through holes.
When the virtual circle circumscribing the outer periphery of the through hole in the region surrounded by the plurality of through holes on the cross section perpendicular to the central axis of the glass sintered body is defined as the second virtual circle, the second virtual circle is defined. The inner diameter of the molding die and the diameter of the hole-forming rod are set so that the diameter of the virtual circle is 14 mm or more and 58 mm or less, and the hole-forming rod is arranged.

Similar to the first aspect, in the production method of the second aspect, the solvent, the curable resin, and the dispersant contained in the molded product can be more efficiently removed in the drying step and the degreasing step.

In the production method of the first or second aspect, when the amount of the quartz glass powder contained in the slurry is 100 parts by weight, the amount of the curable resin is 7.5 parts by weight or more and 11.5 parts by weight. It is preferably less than a part by weight.

By setting the content of the curable resin in the slurry to the above range, the slurry is solidified to a hardness that allows the molding die and the rod for forming holes to be separated from the molded body, while in the degreasing step, Most of the curable resin contained in the molded product can be removed. Therefore, it is possible to suppress the occurrence of cracks in the sintering process.

Further, when a plurality of through holes are formed in the molded body, the strength of the through holes decreases when the distance between the adjacent through holes is short. Therefore, there is a risk of deformation or cracking in any of the steps of removing the molding die and the hole-forming rod from the solidified body, the subsequent drying step, the degreasing step, and the sintering step.
Therefore, in the above-mentioned manufacturing method, when the molded product has a plurality of the through holes, the distance between the closest portions of the two adjacent through holes is 3 mm or more and 58 mm or less. preferable.

When the glass sintered body is used as a preform of an optical fiber, the strength of the glass sintered body or the molded body is ensured at 3 mm, which is the lower limit of the distance between the closest portions of two adjacent through holes. Moreover, when the core through which light passes is inserted into the through hole, the value is set so as not to cause crosstalk between the cores of the optical fiber, and if there is no problem in strength, the above-mentioned The spacing can be less than 3 mm.

Further, the third and fourth aspects of the present invention are:
A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the glass sintered body has one through hole, a virtual circle inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole on a cross section perpendicular to the central axis of the glass sintered body. Of these, the diameter of the virtual circle with the largest diameter is 2a, the outer diameter of the glass sintered body is 2R, the number of through holes is n, the diameter of the through holes is 2r, and the closest contact portion between the through holes. _Bth defined by the following formula (1) when the interval is 2S and the weight part of the curable resin is C when the amount of the quartz glass powder contained in the slurry is 100 parts by weight. So that the value is 73.5 or less
again,
When the glass sintered body has a plurality of through holes, among the virtual circles inscribed in the outer periphery of the glass sintered body and circumscribed in the through holes in the cross section perpendicular to the central axis of the glass sintered body. Of the virtual circle having the maximum diameter and the virtual circle circumscribing the outer periphery of the through hole in the region surrounded by the plurality of through holes on the cross section perpendicular to the central axis of the glass sintered body. The diameter of the virtual circle having a large diameter is 2a, the outer diameter of the glass sintered body is 2R, the number of the through holes is n, the diameter of the through holes is 2r, and the distance between the closest portions between the through holes is 2S. When the amount of the quartz glass powder contained in the slurry is 100 parts by weight and the weight part of the curable resin is C, the _Bth value defined by the following formula (1) is 73. Each step is performed so as to be 5 or less.
B _th = {aC ² ( ^{R2 -} nr2) / (R + nr)} / 1000 ... (1)
(However, R ≧ 15, C ≧ 7.5. A, R, r, S are values when the unit is expressed in mm.)

One of the factors that cause cracks in the molded body in the process from the molded body to the glass sintered body is the amount of curable resin remaining in the molded body in the degreasing step. That is, if the curable resin contained in the molded product cannot be sufficiently removed in the degreasing step, cracks are likely to occur in the degreasing step or the subsequent sintering step. If the amount of the curable resin contained in the molded body is large, it becomes difficult to remove the curable resin from the molded body in the degreasing step, and the residual amount of the curable resin in the molded body increases. Further, when the ratio of the surface area to the volume of the molded body (specific surface area) is small, it becomes difficult for the curable resin to be discharged from the molded body, and the residual amount of the curable resin in the molded body increases. The second aspect of the present invention is based on these findings, and is defined by the above formula (1) as an index showing the susceptibility to cracking (or the difficulty of cracking) in the molded product. It is the one that finds the _Bth value to be obtained. The ratio of the content of the curable resin to the content of the quartz glass powder in the slurry and the maximum virtual circle and the diameter (outer diameter) of the glass sintered body so that the _Bth value is 73.5 or less. By properly managing the factors related to the shape of the glass sintered body, such as the size and arrangement of the through holes, in a well-balanced manner, it is possible to stably produce a quartz glass sintered body without cracks.

Next, an embodiment in which the present invention is applied to a method for manufacturing an optical fiber preform will be described with reference to the drawings.
The optical fiber is formed by spinning an optical fiber preform (hereinafter referred to as a preform). Therefore, the preform is usually designed so that the cross section (cross section) orthogonal to the axial direction thereof is substantially similar to the cross section of the optical fiber. The larger the similarity ratio of the preform to the optical fiber, the longer the optical fiber formed from the preform.

FIG. 1 is a process diagram of a method for manufacturing a glass sintered body according to the present embodiment. In the slurry preparation step (step 1), quartz glass powder, a solvent, a dispersant, and a curable resin are placed in a ball mill and mixed over a predetermined time. Distilled water is usually used as the solvent. The slurry taken out from the ball mill is filled in a molding die after the curing agent is added (step 2). A hole forming rod for forming a through hole of the glass sintered body is arranged in the molding die, and the slurry is filled in the space inside the molding die in which the hole forming rod is not arranged. .. The curable resin is cured by leaving the slurry filled in the mold at room temperature (step 3).

When a molded body is formed in the molding die by curing the curable resin, the molding die and the hole-forming rod are detached from the molded body (step 4). Subsequently, the molded product is dried (step 5), degreased (step 6), and sintered (step 7). In the drying step, the solvent (distilled water) in the molded body is mainly removed, and in the degreasing step, the curable resin in the molded body is mainly removed. Further, the molded body becomes a glass sintered body by the sintering process. A core material is inserted into the through hole of the glass sintered body to form a preform, and the preform is spun to obtain an optical fiber. In any of the drying step, the degreasing step, and the sintering step, appropriate temperature conditions are set according to the composition of the slurry.

2 to 6 are cross-sectional views of a glass sintered body having through holes obtained by the method for manufacturing a glass sintered body according to the present embodiment. FIG. 2 shows a cross section of the glass sintered body 100 having one through hole 10, FIG. 3 shows a cross section of the glass sintered body 200 having two through holes 10, and FIG. 4 shows 4 The cross section of the glass sintered body 300 having the through holes 10 is shown in FIG. 5, the cross section of the glass sintered body 400 having the five through holes 10 is shown in FIG. 5, and the cross section of the glass sintered body 400 having the five through holes 10 is shown in FIG. The cross section of the glass sintered body 500 having is shown respectively. In each molded body, at a position where the central axis of the glass sintered body coincides with the central axis of the through hole 10 (FIGS. 2 and 6), or at a position rotationally symmetric with respect to the central axis of the glass sintered body (FIGS. 3 to 6). 6) The through hole 10 is arranged. The region of the cross section of each glass sintered body excluding the through hole 10 (the region where the hatching pattern is displayed in FIGS. 2 to 6) corresponds to the clad layer of the optical fiber. Hereinafter, this region is referred to as a clad region 20.

A circle inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole 10 is assumed in the clad region 20 of each glass sintered body, and the circle having the largest diameter is hereinafter defined as a virtual circle 30. do. The virtual circle 30 corresponds to the maximum virtual circle of the present invention. For example, in a glass sintered body 100 having one through hole 10, when the central axis of the through hole 10 and the central axis of the glass sintered body 100 coincide with each other, the inside of the outer periphery of the glass sintered body 100 is inside. There is only one type of circle that touches and circumscribes the through hole 10, and this circle is the virtual circle 30. Further, in the case of a glass sintered body 200 having two through holes 10, when the two through holes 10 are arranged at positions symmetrical with respect to the central axis of the glass sintered body 200, the glass is sintered. There are a plurality of types of circles (circles with reference numerals 30 and 31 in FIG. 5) inscribed in the outer periphery of the body 200 and inscribed in the through hole 10. The one with the largest diameter is the virtual circle 30. In the case of the glass sintered body 300 having four through holes 10, the virtual circle 30 is set in the same manner.

In the manufacturing method of the present embodiment, the shrinkage of the molded body from the molded body to the glass sintered body is reduced so that the diameter of the virtual circle 30 set in the clad region 20 of the glass sintered body falls within a predetermined range. In consideration, the outer diameter of the molded body, the inner diameter of the through hole and the arrangement are designed.

In the case of the glass sintered body 100 having one through hole 10 shown in FIG. 2, assuming that the outer diameter thereof is 2R, the inner diameter of the through hole 10 is 2r, and the diameter of the virtual circle 30 is 2a, 2a is as follows. It is expressed by the equation (2) of.
2a = R-r ・ ・ ・ (2)

In the case of the glass sintered body 200 having two through holes 10 shown in FIG. 3, assuming that the distance between the closest portions of the two through holes 10 is 2S, the diameter 2a of the virtual circle 30 is expressed by the following formula. It is represented by (3).
2a = (R ² + S ² + 2rS) / (R + r) ... (3)

In the case of the glass sintered body 300 having four through holes 10 shown in FIG. 4, assuming that the distance between the closest portions of the four through holes 10 is 2S, the diameter 2a of the virtual circle 30 is expressed by the following formula. It is represented by (4).
2a = (R ² -2 (S + r) R + (2S ² + r ² + 4rS)) / (RS) ... (4)
In the above-mentioned equations (2) to (4), the multiplication symbol (x) between the number and the alphabet and between the alphabet and the alphabet is omitted.

In the case of the glass sintered body 400 having the five through holes 10 shown in FIG. 5, assuming that the distance between the closest portions of the two adjacent through holes 10 is 2S, the diameter 2a of the virtual circle 30 is as follows. It is expressed by the equation (5) of.
2a = (R ² -2.75 (S + r) R + (2.89S ² + 1.89r ² + 5.79Sr)) / (R-1.38S-0.38r) ... (5)

However, in the case of the glass sintered body 400 shown in FIG. 5, a circle 31 in contact with the outer periphery of the through holes 10 can be considered inside the five through holes 10. Since this circle 31 does not inscribe the outer periphery of the glass sintered body 400, it does not correspond to a virtual circle by definition, but when the diameter 2b of this circle 31 is larger than the diameter 2a of the virtual circle 30, The outer diameter of the molded body 400, the inner diameter of the through hole 10, and the arrangement are designed so that the diameter 2b of the circle 31 is within a predetermined range instead of the virtual circle 30. The diameter 2b of the circle 31 is represented by the following equation (6).
2b = 3.40S + 1.40r ... (6)

Further, in the case of the glass sintered body 500 having the seven through holes 10 shown in FIG. 6, if the distance between the closest portions of the two adjacent through holes 10 is 2S, the diameter 2a of the virtual circle 30 is , Expressed by the following equation (7).
2a = (R ² -3.46 (S + r) R + (4S ² + 3r ² + 8Sr)) / (R-1.73S-0.73r) ... (7)

In FIGS. 2 to 6, in the cross section of the glass sintered body, through holes are arranged at positions rotationally symmetric with respect to the central axis of the glass sintered body, and if there are a plurality of through holes, they penetrate through them. An example in which the diameters of the holes are equal is shown. On the other hand, in the case of a glass sintered body having through holes having different diameters or having through holes at positions that are not rotationally symmetric, the diameter of the virtual circle cannot be expressed by the above equation. In such a case, the maximum virtual circle may be specified from the shape of the cross section of the glass sintered body and its diameter may be measured. Further, even when a through hole is arranged at a position to be rotated with respect to the central axis of the glass sintered body, the maximum virtual circle is specified from the shape of the cross section of the glass sintered body, and its diameter is determined. You may measure it. In this method, the diameter of the virtual circle can be obtained regardless of the number of through holes and the uneven shape and arrangement of the through holes.

Further, in the manufacturing method of the present embodiment, each step from demolding to sintering is performed so that the _Bth value represented by the above-mentioned formula (1) is 73.5 or less. In the formula (1), when the through hole of the glass sintered body includes a through hole having a diameter different from that of other through holes, or when the arrangement of the through holes is rotationally symmetric with respect to the central axis of the glass sintered body. If not, the diameter 2r of the through hole, which is a variable included in the equation (1), may be the average value of the diameters of the plurality of through holes, and the minimum value among the intervals of the adjacent through holes may be the interval S. ..

Next, an example in which a glass sintered body is actually manufactured by the method shown in FIG. 1 will be described.

[Manufacturing Example 1]
In Production Example 1, two types of glass sintered bodies, Sample 1 and Sample 2, were produced. The temperature conditions of the quartz glass powder, distilled water, curable resin, formulation of dispersant, drying step, degreasing step and sintering step contained in the slurry of Samples 1 and 2 are as shown in Table 1 below. All temperature conditions indicate the peak temperature.

In Sample 1, a molding die having an outer diameter (diameter) of 30 mm and an axial length of 400 mm was used so as to obtain a columnar glass sintered body having no through holes. In Sample 2, a molding die having an outer diameter of 90 mm and an axial length of 160 mm was used so as to obtain a columnar glass sintered body having no through holes. When the presence or absence of cracks in the drying step, the degreasing step, and the sintering step was examined for these samples 1 and 2, the sample 1 did not generate cracks in any of the steps, whereas the sample 2 showed no cracks. Cracks occurred during the sintering process. It is presumed that this is because the curable resin was not sufficiently removed in the degreasing step and remained inside in the sample 2 in which the outer diameter of the glass sintered body was large and therefore the outer diameter of the molded body was large.

From the above results, when a columnar glass sintered body is produced by the conventional slurry formulation as shown in Table 1 or the conventional slurry casting method as shown in Table 1, the outer diameter of the glass sintered body is large. It was found that if the dimensions of the molding die were set so as to be 30 mm or less, cracking did not occur in any of the steps. Further, from Production Example 1, it was presumed that the axial length of the molded product had almost no effect on the susceptibility to cracking.
The outer diameter of the glass sintered body having no through hole can be regarded as the diameter of the virtual circle 30 set in the clad region 20 of the cross section of the glass sintered body having the through hole shown in FIGS. 2 to 6. can. That is, if the outer diameter of the molded body, the inner diameter of the through hole, and the arrangement of the through hole are designed so that the diameter of the virtual circle is 30 mm or less from the result of Production Example 1, the distilled water contained in the molded body is dried. It was speculated that the curable resin could be removed in the degreasing step.

[Manufacturing Example 2]
In Production Example 2, three types of glass sintered bodies, Samples 3 to 5, were produced. The temperature conditions of the quartz glass powder, distilled water, curable resin, formulation of dispersant, drying step, degreasing step and sintering step contained in the slurry of Samples 3 to 5 are as shown in Table 2 below. The temperature conditions of the drying step and the sintering step of Production Example 2 are the same as those of Production Example 1, but the temperature conditions of the degreasing step are slightly different between Production Example 1 and Production Example 2. That is, both Production Examples 1 and 2 have a common point that the peak temperature of the degreasing step is 850 ° C., but Production Example 2 takes longer time to reach the peak temperature than Production Example 1.

In Sample 3, a molding die having an outer diameter (diameter) of 90 mm and an axial length of 70 mm was used so as to obtain a columnar glass sintered body having no through holes. In sample 4, a molding die capable of obtaining a cylindrical glass sintered body having an outer diameter (diameter) of 90 mm, an axial length of 160 mm, and four through holes having an inner diameter of 20 mm inside. Was used. In sample 5, a molding die capable of obtaining a cylindrical glass sintered body having an outer diameter (diameter) of 90 mm, an axial length of 160 mm, and seven through holes having an inner diameter of 20 mm inside. Was used. That is, in sample 4, a molding die in which four hole-forming rods were arranged was used, and in sample 5, a molding die in which seven hole-forming rods were arranged inside was used.

7 (a) to 7 (c) show the cross sections of the glass sintered bodies 601, 610, 620 of the samples 3 to 5. As shown in FIG. 7B, in the sample 4, the diameter of the virtual circle 30 set in the clad region 20 of the glass sintered body 410 is 26 mm, and the distance between the closest portions of the adjacent through holes 10 is 6 mm. As described above, a molding die in which four hole forming rods were arranged was used.

Further, in the sample 5, seven holes are formed so that the diameter of the virtual circle 30 set in the clad region 20 of the glass sintered body 420 is 18 mm and the distance between the closest portions of the adjacent through holes 10 is 5 mm. A molding die in which a rod was arranged was used.

When the presence or absence of cracks in the drying step, the degreasing step, and the sintering step was examined for the above samples 3 to 5, the molded bodies of the samples 3 and 4 were not cracked in the drying step, but the degreasing step was performed. The molded body was cracked, and the glass sintered body was cracked in the subsequent sintering process. On the other hand, in sample 5, no cracks occurred in the molded body and the glass sintered body in any of the steps. From the above results, in the formulation of Production Example 2 and the temperature conditions of each process, the diameter of the virtual circle defined in the cross section of the glass sintered body should be 18 mm or less to suppress the occurrence of cracks. It can be said that it is preferable.

[Manufacturing Example 3]
In Production Example 3, glass sintered bodies of five types of samples 4, 6 to 9 were produced. The temperature conditions of the quartz glass powder, distilled water, curable resin, formulation of dispersant, drying step, degreasing step and sintering step contained in the slurry of Samples 4 and 6 to 9 are as shown in Table 3 below. The temperature profiles of the drying step and the sintering step were the same as those of Production Examples 1 and 2. The temperature profile of the degreasing step was the same as that of Production Example 2. Sample 4 is a glass sintered body manufactured under the same conditions as Sample 4 used in Production Example 2.

All of these five types of samples had the same conditions except that the amount of resin was different with respect to 100 g of quartz glass contained in the slurry.
As described in the column of Production Example 2, the sample 4 did not crack in the molded body in the drying step, but cracks occurred in the molded body in the degreasing step, and the glass sintered body cracked in the subsequent sintering step. Has occurred. Further, in the samples 8 and 9, the molded body was cracked in the drying step (therefore, the degreasing step and the sintering step after the drying step could not be performed). On the other hand, in the samples 6 and 7, no cracks occurred in the molded body and the glass sintered body in any of the steps.

From the above results, it was found that if the amount of the curable resin contained in the slurry was large, the curable resin could not be sufficiently removed in the degreasing step, and as a result, cracks occurred in the sintering step. It was also found that when the amount of the curable resin was small, the molded product cracked in the drying process. In other words, it was found that the occurrence of cracks in the process from the molded body to the glass sintered body can be suppressed by appropriately setting the amount of the curable resin contained in the slurry.

Based on the results of Production Examples 1 to 3, the reason why the molded body and the glass sintered body were cracked in any of the drying step, the degreasing step, and the sintering step was examined. In examining the reason, the calculated values of the maximum virtual circle diameter 2a (mm) and _Bth value of Samples 1 to 9 were referred to. Table 4 shows the calculated values of the maximum virtual circle diameter 2a (mm) and _Bth value of Samples 1 to 9. In Table 4, in addition to the diameter 2a (mm) of the maximum virtual circle of samples 1 to 9 and the calculated _Bth value, the quartz glass powder, distilled water, curable resin, and dispersant contained in the slurry of each sample are shown. The temperature conditions of the formulation, drying step, degreasing step and sintering step of the above are also shown.

In the case of a glass sintered body having no through hole, the outer diameter of the glass sintered body was defined as the diameter of the maximum virtual circle.

Of the above samples 1 to 9, in the samples 1 to 5 in which the amount of resin with respect to 100 g of quartz glass was 11.7 g, the samples 1 and 5 in which cracks did not occur in any of the drying step, the degreasing step, and the sintering step. The B _th values were 30.7 and 14.2, respectively, but the B _th values of the cracked samples 2 to 4 were 276.7, 276.7, and 34.0, respectively. From this, it was speculated that if the glass sintered body is manufactured under the condition that the _Bth value is 34 or less, a good glass sintered body without cracks can be obtained.

On the other hand, the B _{th value of the sample 8 was 12.3 and the B th value} of the sample 9 was 8.7, both of which had a B _th value of 34 or less, but cracks occurred during the drying step. In Sample 8 and Sample 9, the amount of resin per 100 g of quartz glass is 7.1 g and 5.8 g, and the ratio of resin is lower than that of other samples. If the amount of the resin is small with respect to 100 g of quartz glass, it takes a long time to dry, so it is considered that the molded product was cracked during the drying process.

[Manufacturing Example 4]
In Production Example 4, seven sample 10 to 16 glass sintered bodies were produced. The temperature conditions of the quartz glass powder, distilled water, curable resin, formulation of dispersant, drying step, degreasing step and sintering step contained in the slurry of the samples 10 to 16 are as shown in Table 5 below. Further, in Production Example 4, the temperature profile of the drying step was the same as that of Production Examples 1 to 3, and the temperature profile of the degreasing step was the same as that of Production Examples 2 and 3.

In Production Example 4, the temperature profile of the sintering step was the same as that of Production Examples 1 to 3 except that the peak temperature was different. Specifically, in Production Examples 1 to 3, the peak temperature of the sintering step was set to 1500 ° C., but in Production Example 4, the peak temperature of the sintering step was set to 1550 ° C.

Table 5 also shows the calculated values of the diameter 2a (mm) and the _Bth value of the maximum virtual circles of the samples 10 to 16.
Samples marked with "x" in the "cracking (○: none, ×: yes)" column in Table 5 indicate that cracking occurred in any of the drying process, degreasing process, and sintering process. The process in which the crack occurred is described in the remarks column.

As shown in Table 5, in the sample 14, the molded body did not crack in the drying step, but cracks occurred in the molded body in the degreasing step, and the glass sintered body cracked in the subsequent sintering step. occured. In the sample 15, the molded body did not crack in the drying step, but cracks occurred in the molded body in the degreasing step (therefore, the sintering step after the degreasing step was not performed). In the sample 16, the molded body was cracked in the drying step (therefore, the degreasing step and the sintering step after the drying step could not be performed). On the other hand, in the samples 10 to 13, no cracks occurred in the molded body and the glass sintered body in any of the steps.

From the results of Production Examples 1 to 4, the following were presumed as conditions for obtaining a good glass sintered body without cracks.
(1) The diameter of the maximum virtual circle is 58.0 mm or less.
(2) The amount of resin per 100 g of quartz glass contained in the slurry should be more than 7.1 g and less than 11.7 g.
(3) Set the shape of the glass sintered body so that the B _th value is 73.5 or less.
(4) When the glass sintered body has a plurality of through holes, the distance between the closest portions of the adjacent through holes shall be 58.0 mm or less.
The lower limit of the diameter of the maximum virtual circle, the lower limit of the _Bth value, and the lower limit of the distance between the adjacent portions of the adjacent through holes are determined according to the mechanical strength required for the glass sintered body.

The present invention is not limited to the above-described embodiment, and can be appropriately modified.
For example, in the above embodiment, a manufacturing example of a glass sintered body having a circular cross section (that is, a columnar glass sintered body) has been described, but the present invention is not limited to this, and a columnar glass sintered body having a polygonal cross section may be used. In the case of manufacturing, the cross-sectional shape is generally circular, but the manufacturing method of the present invention can also be applied when manufacturing a columnar glass sintered body in which a part of the outer peripheral surface is a flat surface. Is.
Further, a part or the whole of the outer peripheral surface of the columnar molded body obtained in the drying step of the manufacturing method of the present invention is scraped to make a flat surface, and the molded body is degreased, sintered and glass sintered. You may try to get a body.

10 ... Through hole 20 ... Clad area 30 ... Virtual circle 100, 200, 300, 400, 500, 601, 610, 620 ... Glass sintered body

Claims (4)

A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the amount of the quartz glass powder contained in the slurry is 100 parts by weight, the amount of the curable resin is 7.5 parts by weight or more and 11.5 parts by weight or less.
The glass sintered body has a plurality of through holes, and the glass sintered body has a plurality of through holes.
On a cross section perpendicular to the central axis of the glass sintered body, a virtual circle inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole, and the plurality of through holes on the cross section. In the enclosed area, the inner diameter of the molding mold and the hole formation so that the diameter of the maximum virtual circle having the maximum diameter among the virtual circles circumscribing the outer periphery of the through hole is 14 mm or more and 58 mm or less. A method for manufacturing a glass sintered body, wherein the diameter of the rod for forming is set and the rod for forming a hole is arranged. In the method for manufacturing a glass sintered body according to claim 1 ,
A method for manufacturing a glass sintered body, wherein the distance between the closest portions of two adjacent through holes is 3 mm or more and 58 mm or less. A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the mold accommodating portion having a cylindrical accommodating portion in which a columnar hole-forming rod is arranged, and the curable resin is filled. And the process of curing
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces. ,
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the amount of the quartz glass powder contained in the slurry is 100 parts by weight, the amount of the curable resin is 7.5 parts by weight or more and 11.5 parts by weight or less.
When the glass sintered body has one through hole, a virtual circle inscribed in the outer periphery of the glass sintered body and circumscribed in the through hole on a cross section perpendicular to the central axis of the glass sintered body. Of these, the diameter of the virtual circle with the largest diameter is 2a, the outer diameter of the glass sintered body is 2R, the number of through holes is n, the diameter of the through holes is 2r, and the closest contact portion between the through holes. _Bth defined by the following formula (1) when the interval is 2S and the weight part of the curable resin is C when the amount of the quartz glass powder contained in the slurry is 100 parts by weight. A method for manufacturing a glass sintered body, in which each step is performed so that the value is 73.5 or less.
B _th = {aC ² ( ^{R2 -} nr2) / (R + nr)} / 1000 ... (1)
(However, R ≧ 15, C ≧ 7.5. A, R, r, S are values when the unit is expressed in mm.) A slurry containing quartz glass powder, a dispersant, a curable resin, and a solvent is filled in the accommodating portion of a mold having a tubular accommodating portion in which a pore-forming rod is arranged, and the curable resin is cured. Process and
After the slurry in the molding die is solidified, the molding die and the hole forming rod are separated from the solidified body of the slurry to obtain a columnar molded body having through holes penetrating both end faces.
The step of drying the molded product and
The step of degreasing the dried molded product and
A method for producing a glass sintered body having through holes, which comprises a step of sintering the degreased molded body.
When the amount of the quartz glass powder contained in the slurry is 100 parts by weight, the amount of the curable resin is 7.5 parts by weight or more and 11.5 parts by weight or less.
The glass sintered body has a plurality of through holes, and the glass sintered body has a plurality of through holes.
On a cross section perpendicular to the central axis of the glass sintered body, a virtual circle inscribed in the outer circumference of the glass sintered body and circumscribed to the through hole, and the plurality of through holes on the cross section. In the enclosed area, among the virtual circles that do not inscribe the outer periphery of the glass sintered body and circumscribe the outer periphery of the through hole, the diameter of the maximum virtual circle having the maximum diameter is 14 mm or more and 58 mm or less. A method for manufacturing a glass sintered body, wherein the inner diameter of the molding die and the diameter of the hole forming rod are set so as to be, and the hole forming rod is arranged.

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