JP2005132647A - Manufacturing method of rod-like ceramic body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a firing tool which reduces cracks and amount of warpage at degreasing of a molded product obtained using a resin binder. <P>SOLUTION: Uniform degreasing of the rod-like ceramic molded product is realized by using the grooved firing tool made of a porous ceramic having a porosity of 65-75% . <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a rod-shaped ceramic body necessary for obtaining a rod-shaped ceramic sintered body with good straightness.

  In recent years, optical communication using an optical fiber has been used with an increase in the amount of information in communication. In this optical communication, an optical connector is used to connect optical fibers or connect an optical fiber and various optical elements.

  For example, in the case of a connector for connecting optical fibers, the end face of the optical fiber is processed into a convex spherical shape by holding the end of the optical fiber in a through hole formed in the ferrule and inserting a pair of ferrules from both ends of the sleeve It has a structure in which they are brought into contact with each other.

  Various materials such as ceramic, metal, plastic, and glass have been made as materials for the ferrule and sleeve, but most of them are made of ceramic at present. The reason for this is that ceramic has high processing accuracy, so the tolerance of the inner and outer diameters can be as high as 1 μm or less, and ceramic has a low coefficient of friction, so it has excellent optical fiber insertability, high rigidity, and high heat. This is because the expansion coefficient is low, so that it is stable against external stress and temperature change, and has excellent corrosion resistance.

  Further, in recent years, the majority of ceramics is being replaced by zirconia from alumina. This zirconia sintered body has a low Young's modulus, which is about half that of alumina, so that when the tip surfaces of two ferrules are brought into contact with each other, the adhesion can be increased with a small stress, and the strength and toughness must be high. Therefore, reliability can be improved (Patent Document 1).

  Such a zirconia sintered body is manufactured, for example, by manufacturing a rod-shaped zirconia molded body by an extrusion molding method, and degreasing and firing the rod-shaped zirconia molded body. In this firing step, the zirconia compact is placed on a firing jig provided with a plurality of grooves on a ceramic flat plate and degreased.

  Conventionally, low-purity alumina called refractory bricks has been used as a material for firing jigs. This is because the heat resistance is so high that this material is used also as a furnace wall material, and as a result, it is excellent in durability.

This firing jig using low-purity alumina was manufactured by filling a press mold provided with grooves with low-purity alumina raw material powder, press-molding, and firing the powder.
Japanese Patent Publication No. 8-30775

  However, the molded body using the resin binder has a drawback that cracks are likely to occur during degreasing. If this crack exists even if it is minute, it becomes a defective product, so the degreasing process can be said to be the most important process. As a crack generation process, since the resin binder gas does not escape from the molded body uniformly, the molded body is distorted and cannot be tolerated. The material of the conventional jig is a refractory brick with poor air permeability. Since the gas escape path is blocked on the grounding surface of the jig and the molded body, cracks are likely to occur from this point.

  In addition, by installing the molded body on the groove and degreasing, there is a problem that the degreasing body is bent due to a difference in the degreasing ease between the contact surface with the jig and the exposed surface. It was. Therefore, in consideration of the bending of the sintered body, a large machining cost has to be taken.

  Therefore, the present invention has been made in view of the above problems, and a rod-shaped ceramic molded body formed using a resin binder is installed in a ceramic firing jig made of porous ceramic having a porosity of 65 to 75%. Then, the resin binder is degreased by firing to form a rod-shaped ceramic body.

  In addition, the firing jig is characterized in that the plane is made of a rectangular plate-like body, and a plurality of grooves are provided in the entire longitudinal direction.

Furthermore, the ratio of the straightness in the groove longitudinal direction to the groove length is 6 × 10 ⁻⁴ or less.

  That is, by making the jig material good in air permeability, the degreasing property on the contact surface can be improved and the molded body can be degreased uniformly.

According to the configuration of the present invention, when manufacturing a rod-shaped ceramic sintered body, the resin binder is degreased by a firing jig having a porosity of 65 to 75%. Resin binders can be easily removed from the contact surface through the pores, which improves air permeability and makes the contact surface and exposed surface of the rod-shaped ceramic molded body with the firing jig easier to degrease and form. The body can be degreased uniformly. As a result, it is possible to obtain a rod-shaped ceramic body with no cracks and improved straightness.

  The best mode for carrying out the present invention will be described.

  According to the method for producing a rod-shaped ceramic of the present invention, a rod-shaped ceramic molded body formed by using a resin binder is placed on a ceramic firing jig made of porous ceramic having a porosity of 65 to 75%, and then the above resin is fired. A rod-shaped ceramic body is formed by degreasing the binder.

  The rod-shaped ceramic molded body used in the production method of the present invention is mainly composed of ceramic powder and a binder resin.

  As the ceramic powder, zirconia or alumina is used, and as the binder resin, benzene, ester, or the like is used.

  To manufacture a ceramic firing jig, for example, a ceramic refractory powder such as alumina and water are mixed with benzene resin as a main raw material, and further an additive such as a hydrophilic urethane polymer is mixed for foaming. . This ratio is added so that the additive is preferably 5 to 15 parts by weight when the total amount of the refractory powder and the additive is 100 parts by weight. The slurry obtained by mixing is reacted in a mold and foamed and cured. This is degreased and fired, and a plate-like ceramic flat plate as a material for the firing jig is completed.

  Next, this is subjected to a plurality of grooves with a surface grinder shown in FIG. In detail, the ceramic flat plate 1 produced as described above is fixed to the bed 3 and lowered along the column 4 while rotating the diamond tool 2 that fits the groove 1a, and a groove is dug in the longitudinal direction. Thus, the firing jig 1 shown in FIG. 1 is completed.

  Here, the evaluation of the porosity of the firing jig 1 will be described. As shown in JIS R 2614-1985, the true specific gravity d0 of the firing jig and the bulk specific gravity d thereof are obtained. Thereby, the porosity P is calculated by the following formula.

P = (1-d / d0) × 100
The porosity P, which is an important parameter of this patent, affects the amount of hydrophilic urethane polymer added when mixing raw materials. If this addition amount is 15 parts by weight or more, the porosity becomes 75% or more, the resin binder is easily removed, the rate of occurrence of cracks in the molded product during degreasing is reduced, and it is also effective against warping. In addition, since the durability of the jig itself is lowered due to the decrease in density, the limit is preferably up to 15 parts by weight. In addition, when the addition amount is less than 5 parts by weight, the porosity of the jig is 65% or less, and the maximum advantage of the present invention, which is not effective in improving the air permeability during degreasing, the lower limit is set to 5 parts by weight. .

Since the ferrule for SC connector which is generally used has an outer diameter of 2.5 mm and a length of 10.5 mm, it is desirable that the zirconia sintered body before processing has a length of 15 mm and a warp amount of 15 μm or less. Yes. That is, the ratio of the warp to the length of the zirconia sintered body needs to be 1 × 10 ^C or less.

As described above, the warpage of the zirconia sintered body depends on the straightness in the groove longitudinal direction of the firing jig. At the same time, however, the warpage increases due to the density variation of the dried zirconia and the temperature non-uniformity in the firing furnace. Therefore, in consideration of these influences, the ratio of the straightness of the groove longitudinal direction to the groove length of the firing jig must be smaller than 1 × 10 ⁻³ , and as a result of various experiments, this ratio is 6 It has been found that it may be set to x10 ⁻⁴ or less. That is, when the ratio S / L of the straightness S in the longitudinal direction of the groove to the groove length L of the firing jig exceeds 6 × 10 ⁻⁴ , the warp of the sintered body becomes large. A more preferable range of this ratio is 4.9 × 10 ⁻⁴ or less.

  Here, the evaluation of the warpage of the rod-shaped ceramic sintered body will be described. When a rod-shaped ceramic sintered body having a warp is placed on the surface plate, a gap is formed between the surface plate and the rod-shaped ceramic sintered body. When the rod-shaped ceramic sintered body is rotated, this gap is maximized at a certain point. This maximum gap is defined as “sledge”. This maximum gap is measured by inserting a gap gauge into the gap.

Further, the straightness of the firing jig in the longitudinal direction of the groove is evaluated as follows. First, the stylus is applied to the groove 1a and moved in the longitudinal direction. Record the deflection of the stylus at that time, and use the difference between the maximum and minimum values as straightness. At this time, the short-period vibration due to the roughness of the surface is not taken into consideration, and only the long-period vibration due to the overall waviness is evaluated. In the present invention, the ratio of the straightness in the longitudinal direction to the length of the groove 1a is set to 6 × 10 ⁻⁴ or less.

When such a firing jig having a good straightness in the longitudinal direction of the groove is used, warpage of the fired rod-shaped zirconia sintered body is small, and the ratio of warpage to the length of the zirconia sintered body is 1 × 10 ⁻³ or less. Thus, there is no adverse effect on workability in the subsequent ferrule manufacturing process.

  In addition, if the angle of the groove 1a is too large, the pinching property of the groove side surface is weakened. If it is too small, the groove becomes too deep to obtain the required groove width, which increases the strength of the firing jig or the firing durability. In view of adverse effects, 45 ° to 100 ° is preferable. The width of the groove 1a is preferably 0.8 to 1.1 times the diameter of the rod-shaped ceramic dried body on the surface of the ceramic flat plate 1. This is because, as the width of the groove 1a is wider, the rod-shaped ceramic dried body can be easily and stably placed, but the processing requires much manpower.

  By forming the groove 1a by the above processing method, the firing jig of the present invention is obtained.

  The firing jig according to the present invention has been described with reference to ceramic parts for optical communication, but is not limited thereto, and can be widely used for all rod-shaped ceramic parts that require a sintered body with less warpage.

  Examples of the present invention will be described below. 50 parts by weight of water was added to 80 parts by weight of alumina powder having an average particle size of 0.6 μm and wet-mixed to obtain a slurry. To this slurry, 15 parts by weight of a hydrophilic urethane polymer is added, and the mixture is poured into a mold having a predetermined size, foamed and cured, and this is degreased and fired to obtain a length of 200 mm, a width of 200 mm, A flat plate-shaped test body 1 having a thickness of 10 mm was obtained. Moreover, what added the amount of hydrophilic urethane polymer to 20%, 5%, and 1% was made into the test bodies 2, 3, and 4. FIG.

  Further, as a comparative example, a mixed powder of 86 parts by weight of alumina powder and 13 parts by weight of silica powder was prepared, and the above-mentioned shaped alumina ceramic flat plate was manufactured by press molding and firing by a batch furnace.

Separately from these, cubes having a side of 10 mm were prepared from sintered bodies of the materials of the test bodies 1, 2, 3, and 4, and the respective porosities were examined. At this time, the true specific gravity was measured with a helium hydrometer (MULTIVOLME PYCNOMETER 1305, manufactured by Shimazu Seisakusho), and the weight was measured with a weigh scale (Motorola type METTLER AT250). The values are shown in Table 1.

  These flat plate test bodies 1, 2, 3, 4 are machined into a shape having grooves as shown in FIG. 1 using a surface grinder and a diamond tool. In this experiment, a groove width of 3.2 mm and a groove depth of 2. Twenty-six grooves of 8 mm were formed. At this time, processing was performed so that the ratio of the straightness S in the groove longitudinal direction to the groove length L was 6 × 10 −4.

  A rod-shaped ceramic compact was actually installed on these firing jigs, and cracks, warps, and durability were compared. The rod-shaped ceramic molded body used is a mixture of a resin binder and zirconia powder formed into a rod shape having an outer shape of 3.50 mm by extrusion molding. This was cut into a length of 180 mm and installed in all the grooves of each firing jig. The amount of warpage of the molded body produced by the extrusion molding machine is almost the same, and the accuracy is further increased by increasing the number of samples.

  The degreasing conditions are as follows: the temperature is raised to 350 ° C. at 10 ° C./hour, then raised to 450 ° C. at 100 ° C./hour, and held for 1 hour, and a program for natural cooling is set up and degreasing in a batch furnace The experiment was conducted.

After degreasing, the crack generation rate of the rod-shaped ceramic dried body is examined. The occurrence rate is obtained by visually observing 26 rod-shaped ceramic dried bodies and calculating the number of cracks generated per dried body. The results are shown in Table 1. Thus, no crack was observed in the case where the hydrophilic urethane polymer was 5% or more. That is, it can be seen that the firing jig having a porosity of 65% or more has good air permeability during degreasing and ideal degassing is performed.

Moreover, about the amount of curvature, ten pieces were extracted from each jig and measured by the measurement method described above to obtain a ratio to the length. As a result of comparison, they are as shown in Table 3. From this result, it can be seen that the amount of warpage is significantly reduced as compared with the conventional setter. This is also an effect of ideal degassing.

  Next, a durability test of the firing jig was performed. The temperature was raised to 500 ° C. at a rate of temperature increase of 400 ° C./hour, and subjected to a cooling cycle of cooling at a cooling rate of 500 ° C./hour, and the number of cooling cycles in which the amount of warping occurred was examined. When cracks did not occur after 30 cooling cycles, the fact that no cracks occurred was displayed. The results are shown in Table 4. Again, conventional jigs were dense and did not crack. In the firing jig of the present invention, cracks occurred when the amount of the hydrophilic urethane polymer added was 20 parts by weight. After all, it was found that those with too high porosity had a problem with durability. However, those having a weight of 15 parts by weight or less are considered to be able to withstand use because cracks are not generated.

  From the above, it was found that the ceramic molded body using the resin binder can be degreased with high accuracy by using the V-groove firing jig using the porous ceramics having a porosity of 75% to 65%.

It is a perspective view which shows a porous ceramic baking jig. It is a figure which shows a surface grinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic flat plate 1a .. Groove 2 ... Diamond tool 3 ... Bed 4 ... Column

Claims (3)

A rod-shaped ceramic body formed by using a resin binder is placed on a ceramic firing jig made of porous ceramic having a porosity of 65 to 75%, and then the resin binder is degreased by firing to form a rod-shaped ceramic body. A method for producing a rod-shaped ceramic body, characterized by comprising: The method for producing a rod-shaped ceramic body, wherein the firing jig is a plate-shaped body having a rectangular plane and provided with a plurality of grooves in the entire longitudinal direction. 3. The method for manufacturing a rod-shaped ceramic body according to claim 2, wherein a ratio of straightness in the groove longitudinal direction to the groove length is 6 × 10 ⁻⁴ or less.

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