JPH09295872A - Coating agent for sintering jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintering jig good in defatting efficiency and excellent in durability. SOLUTION: This coating agent for sintering jigs comprises a composition which is used for forming a coating layer for preventing the reaction of the sintering jig with a workpiece on the surface of the sintering jig and which consists mainly of a burning agent and zirconia or highly pure alumina containing a stabilizer. The coating agent 2 consisting mainly of the burning agent and the zirconia or highly pure alumina containing the stabilizer is coated on a sintering jig substrate 1 and subsequently sintered under a condition of 1200-1600 deg.C. Thereby, defatting efficiency is improved, and the rate of detective workpiece generation is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent for obtaining an inexpensive and lightweight firing jig which does not easily react with an object to be fired (hereinafter also referred to as a work), has excellent durability, and a coating agent for the same. The invention relates to a firing jig obtained by using the jig.

[0002]

2. Description of the Related Art Conventionally, a mullite or alumina refractory has been used as a firing jig under a high temperature zero atmosphere of about 1000 to 1700 ° C. Further, in recent years, in order to operate the firing furnace more economically and to improve the productivity, in order to perform energy saving operation and high speed operation, the specific gravity of the firing jig has been reduced or the thickness thereof has been reduced. It was On the other hand, a firing jig having a zirconia coating containing a stabilizer such as yttria is also used in order to prevent the reaction between the work to be fired and the firing jig and to prolong the life of the firing jig. Other stabilizers added to the zirconia coating include calcia, magnesia, and ceria.
As an example of a related technique relating to a firing jig having a zirconia coating, a fibrous base material is disclosed in JP-A-2-89989. The stabilizer is appropriately selected depending on the composition of the work to be fired. Further, there is an example of a firing jig in which the base material of the firing jig is mullite or silicon carbide and the reaction preventing film with the work is a high-purity alumina film.

[0003]

The conventional reaction-preventing coating between the work and the firing jig has been formed of a coating having no unevenness and a substantially uniform thickness. The coating agent used for forming this film is composed of zirconia containing a stabilizer in a predetermined ratio or partially stabilized zirconia or alumina and a solvent, and also includes a dispersant, a defoaming agent, and a viscosity adjusting agent. Although the agent was added appropriately,
With this coating agent, the film obtained was flat.

The present invention provides a firing jig and a reaction-preventing coating which have small holes instead of the flat reaction-preventing coating which has been conventionally used, and which are more excellent in the reaction-preventing effect and the degreasing effect in the degreasing process. The present invention provides a coating agent to be formed and a method of using the same.

[0005]

According to the present invention, in order to solve the above-mentioned problems, the invention of claim 1 is characterized in that
A composition for forming a coating layer for preventing a reaction with a work is characterized by mainly containing zirconia or a high-purity alumina containing a stabilizer such as yttria or calcia and a burnout agent. The invention of claim 1 relates to a coating agent capable of forming a reaction-preventing layer when the firing jig has the reaction-preventing layer.

According to a second aspect of the present invention, there is provided a composition for forming a coating layer for preventing reaction with a work on the surface of a firing jig, which comprises zirconia and a water-absorbing polymer containing a stabilizer such as yttria or calcia. It is characterized by having it as a main component. According to the invention of claim 2, when the firing jig has a reaction-preventing layer, the burning agent in the coating agent capable of forming the reaction-preventing layer is a water-absorbent polymer.

Next, the invention of claim 3 is the coating agent according to claim 1 or claim 2 for a firing jig base material selected from mullite, alumina, silicon carbide, cordierite, magnesia spinel and the like. And apply 1200
It is characterized in that it is fired under the condition of 1600 ° C.
The invention of claim 3 is an invention relating to a method for producing a firing jig by using the coating agent according to claim 1 or 2.

According to a fourth aspect of the present invention, in a firing jig including a base material and a coating layer of the base material, the base material is selected from mullite, alumina, silicon carbide and the like, and the coating layer has a diameter of 0.5. Has a hole that is a burnt-out trace of ~ 2 mm on the entire surface,
It is characterized by being a fired layer of a zirconia coating agent containing a stabilizer or a fired layer of a coating agent made of high-purity alumina, which has a minimum coating thickness of 50 to 250 μm. A fourth aspect of the present invention is an invention of a firing jig itself obtained by using the coating agent according to the first or second aspect, for example, by the method of the third aspect.

The invention of claim 5 is characterized in that the firing layer of the coating agent as the reaction preventing layer is formed on both sides of the plate-like firing jig base material. A fifth aspect of the present invention uses the coating agent according to the first or second aspect of the present invention, for example, the firing jig obtained by the method of the third aspect is a plate-like firing, and a reaction-preventing layer is formed on both sides of the firing jig. It is an invention about a jig. The plate shape in the present invention includes a plate having a substantially flat surface or having V-shaped grooves, U-shaped grooves, or wavy unevenness.

The above-mentioned components of the present invention will be described in detail below. The firing jig referred to in this invention is
Ceramic or electronic ceramic parts (insulators, conductors,
Semiconductors, dielectrics, piezoelectrics, magnetic materials, etc.), insulators, cutting
It is a heat-resistant jig that is used when firing abrasive materials, and is called a base plate, shelf plate, setter, sheath, pod, bowl, or column, depending on its shape. Among these,
As a jig that directly contacts the object to be fired (work), a shelf board,
There is a setter. As the base material of these firing jigs, those selected from mullite, alumina, silicon carbide, cordierite, magnesia spinel and the like are used.

One of the main components of the coating agent used for forming the coating layer capable of preventing the reaction with the work is a ceramic component selected from zirconia and high-purity alumina, of which zirconia is crystallized. As a stabilizer for stabilizing the structure into a cubic crystal, 2 to 20% by weight of one or more kinds arbitrarily selected from yttria, calcia, magnesia, ceria, etc. is added or a stabilizer is added in advance. Baked partially stabilized zirconia is used. In the case of high-purity alumina, magnesia for preventing grain growth at high temperature, which is a function different from that of the stabilizer, may be added.

The ceramic component such as zirconia and alumina and the stabilizer serve as a coating agent from a powder having a particle diameter of 0.5 μm to 50 μm. When the particles having a particle size within the range of 10 to 20 μm are used, the coating agent layer has the least problem. This particle size is 0.5μ
When it is less than m, the silica component in the base material reacts with zirconia or alumina when baking the coating layer with the coating agent, which adversely affects the function as a reaction preventing layer with the work when baking the work later. give. on the other hand,
If the particle size is 50 μm or more, the surface of the reaction-preventing layer becomes rough, and although the decomposition gas in the degreasing process has a diffusion effect, the sticking force of the particles themselves becomes weak, and the particles are shattered by handling or contact with the work. May occur. If the particles are shredded, the coating layer of the coating agent will gradually become thinner and the firing jig base material will be exposed. In addition, the work environment becomes powdery and foreign matter may be mixed into the product, which is not good.

The other main component of the coating agent is a burnout agent. Depending on the size of the burned-out trace after firing, the burn-off agent is 0.
The size is selected from 5 to 2 mm. As the substance used for the burnout agent, any substance that is thermally decomposed during firing can be used. The decomposition gas at the time of firing is selected from those that are harmless to the firing jig or the reaction preventive layer, but insoluble in synthetic resin particles containing water-absorbing polymer, rubber particles, spherical carbon, wood chips, rice husks, plant seeds, etc. or solvent Any substance such as oil can be used.

Among the burnout agents, water absorbing polymer particles are particularly excellent. When a water-absorbent polymer is used as a burnout agent, the reason why it is excellent is that the specific gravity after absorbing water is close to 1, the slurry of the coating agent can be easily adjusted, and the burnout agent can be uniformly distributed. . Furthermore, moisture absorption evaporates due to drying and the volume decreases, and the decomposition gas generated during firing of the coating agent is less than other burned materials,
There are no problems such as cracks or peeling during firing of the coating agent. The particle size of the water-absorbent polymer particles is usually 250 μm or less before water absorption. When a water-absorbing polymer having a particle diameter of more than 250 μm is used, the water-absorbing polymer after water absorption has a diameter of several mm,
When the coating layer is formed and fired, the pores tend to be large. On the other hand, when only particles having a particle size of 20 μm or less are used, the holes after firing become smaller than the size of the work, and the effect of forming the holes cannot be seen.

The compositional type of the water-absorbent polymer includes
Modified starch, cellulose-based, acrylonitrile-grafted starch hydrolyzate-based, polyacrylonitrile-derivative-based, polyacrylamide-based and polyacrylate-based, vinyl acetate / methyl acrylate copolymer saponified-based, polyoxyethylene-based Also, the hydrophilic group has a polyoxyethylene chain or a carboxylic acid side chain. In addition, there are crosslinked products of nonionic polymers such as polyvinylpyrrolidone and polyvinyl alcohol, and sulfonic acid polymers such as polystyrenesulfonic acid and poly-2-acrylamido-2-methylpropanesulfonic acid.

The amount of the water absorbing polymer in the coating agent is preferably 0.1 to 2% by weight. If it is less than 0.1% by weight, holes are only partially formed in the firing jig substrate, and the firing effect is the same as that of the conventional product. On the other hand, when the content is 2% by weight or more, the water-absorbent polymer spreads over the entire surface of the firing jig base material, and the surface does not become a flat zirconia layer having pores. FIGS. 1 to 3 schematically show the difference depending on the addition amount of the water-absorbing polymer in the coating agent. In the figure, the upper part shows the coating material in a wet state, while the lower part shows the coating material when it is dried. FIG. 1 shows a cross section of the firing jig base material and the coating agent layer when the amount of the water absorbing polymer is in the range of 0.1 to 2% by weight. In the figure, reference numeral 1 is a firing jig base material, and 2 is a coating agent. Reference numeral 3 is a water-absorbing polymer in a water-absorbing state. In the dry state in the lower part, the volume of the water-absorbent polymer is remarkably reduced, so that the illustration is omitted. 2 and 3 characteristically show the amount of the water-absorbing polymer added below 0.1% by weight and above 2% by weight. FIG. 4 shows cross-sectional views before and after drying when a coating material containing no water-absorbing polymer is applied to a conventional firing jig base material having a flat surface.

In the present invention, the coating agent is, in addition to the non-reactive ceramic, the stabilizer, and the water-absorbing polymer, water as a dispersion medium, a dispersing agent, a wetting agent, a defoaming agent, and a surfactant such as a foaming agent. , Methyl cellulose, polyvinyl alcohol, hydroxymethyl cellulose, sodium polyacrylate, guar gum and other thickeners are appropriately added to obtain a viscosity of 10
It is used in a slurry form of 00 cps to 4000 cps. The nonvolatile content of this slurry coating agent is
It is adjusted to about 40 to 80%. This water content is 60%
When it is larger, the water absorption of the substrate is small, and unless the coating is repeated many times, the thickness of the coating layer of the coating agent does not reach 50 μm or more, resulting in poor efficiency. Also,
If it is less than 20%, the viscosity becomes large and it becomes difficult to coat, which is not good.

The coating agent is applied to the firing jig base material,
For coating, a coating layer is formed by a known coating means. Examples of the coating means include spray gun, knife coater, roll coater, and dipping. At this time, coating thickness (amount) with the coating agent
Is 70-350 μm (0.02-
0.2 g / cm ² ) is preferable. When the coating thickness (amount) is in this range, the thickness of the coating layer after firing is 50 to 25
It becomes 0 μm, and the function as a reaction prevention layer with the work is
Will be obtained. When the thickness of the coating layer is less than 50 μm, the reaction layer of the coating layer and the firing jig base material is formed on the surface, and there is a problem in the effect of preventing the reaction with the work. On the other hand, when the thickness of the coating layer is more than 250 μm, cracks are generated in the coating layer itself during firing, a reaction may be seen in the exposed portion of the base material, or peeling of the coating layer is not preferable. The coating layer is baked at 1400 ° C.
It is appropriately selected from the range of ± 200 ° C. according to the sintering temperature of the ceramic component. If the firing temperature is lower than the predetermined firing temperature, the adhesion to the firing jig base material is insufficient, and conversely, if the firing temperature is too high, the reaction with the firing jig base material greatly progresses. Or, the reaction preventing layer is peeled off from the substrate. By firing the firing jig base material including the coating layer of the coating agent, it is possible to obtain a fired trace of the burn-off agent having a diameter of 0.5 to 2 mm formed on the surface of the firing jig.

The coating layer is preferably formed on both surfaces of the baking jig substrate when it is a plate-like material. This is because when the coating layer is fired, stress is generated in the firing jig base material, and even if stress occurs, there is a thickness that does not deform,
One-sided formation is also possible as long as it has strength to withstand stress. FIG. 7 is a schematic cross-sectional view of a plate-shaped firing jig having reaction prevention layers formed on both sides.

[0020]

In the present invention, by incorporating the burnout agent particles in the coating agent, pores are formed in the coating layer and the number of contact points with the work is reduced, so that the reaction becomes difficult. Moreover, since the work shrinks during firing, it is more accurate to support it at a point rather than by supporting it on the surface. A space can be provided under the work, and sublimation and evaporation components generated from the work can be stored. Further, even in the case of a work having a large amount of binder component, not only degreasing from the upper surface but also degreasing from the lower surface can be performed, and it is not necessary to lengthen the debinding process.

[0021]

Example 1 A coating agent 1 was prepared with the following composition. Water 31 parts by weight Dispersant 1 part by weight Water-absorbent polymer 0.4 parts by weight Calcia-stabilized zirconia 66 parts by weight Binder 1.6 parts by weight ──────────────────── ────────── 100 parts by weight

In Example 1, the dispersant used was Poise 520, trade name, manufactured by Kao Corporation, the water-absorbing polymer was Sumikagel S-100, trade name, manufactured by Sumitomo Chemical Co., Ltd., and calcia-stabilized zirconia was the first. Product name F of Rare Element Chemical Industry Co., Ltd.
SD-350F having an average particle size of 3.0 μm, and a binder used was WA-310, a trade name of Mitsui Toatsu Chemicals, Inc. The coating agent mixed at these ratios was dispersed for 24 hours with a ball mill, and was applied with 200 μm (0.1 g / cm ² ) on both sides of a mullite substrate using a spray gun. Also, dried at 130 ° C for 1 hr, 1500 ° C
Firing was performed at a raising / lowering temperature of 200 ° C./hr.

When a work of a barium titanate-based capacitor containing a large amount of binder was fired using the mullite firing jig having this coating layer, the proportion of defective products was higher than that when no water-absorbing polymer was used. But the whole 1
% To 0.05%, and the product yield was improved.

[0024]

Example 2 A coating agent 2 was prepared with the following composition. Water 25 parts by weight Dispersant 0.5 parts by weight Water-absorbing polymer 1 part by weight Alumina powder 70 parts by weight Binder 3.5 parts by weight ─────────────────────── ──────── 100 parts by weight

In Example 2, as the dispersant, Cerna D-305 manufactured by Chukyo Yushi Co., Ltd., whose main component is polyacrylic acid ammonium salt, was used, and the water-absorbing polymer was manufactured by Mitsubishi Chemical Co., Ltd. IH and alumina powder are Sumitomo Chemical Co., Ltd.
Trade name AM-25, a binder used was trade name SUM-4100 manufactured by Showa High Polymer Co., Ltd. The coating agent mixed at these ratios was dispersed by a ball mill for 48 hours, and was applied to a mullite or magnesia spinel substrate with a brush by 300 μm (0.15 g / cm ² ). Also, dried at 130 ° C for 1 hr, 1600 ° C
It was fired at (elevating temperature 100 ° C./hr).

With this substrate, when the ceramics were fired, the fusion with the coating agent was reduced compared with the conventional one, and the number of times of re-coating required was greatly reduced.

[0027]

Example 3 A coating agent 3 was prepared with the following composition. Water 33 parts by weight Dispersant 1 part by weight Burning agent 4 parts by weight Calcia stabilized zirconia 60 parts by weight Binder 2 parts by weight ────────────────────────── ───── 100 parts by weight

In Example 3, the dispersant used in Example 1
Calcia-stabilized zirconia and a binder were used, and as the burning agent, low-density polyethylene trade name Flow Beads CL-12007 manufactured by Sumitomo Seika Chemicals Co., Ltd. and an average particle size of 850 μm were used. The coating agent mixed at these ratios was dispersed by a ball mill for 24 hours, and was sprayed onto a mullite substrate at 200 μm (0.1 g / c) using a spray gun.
m ² ) applied. Moreover, what was dried at 130 ° C. for 1 hour was calcined at 1500 ° C. (rising temperature 200 ° C./hr).

Also in Example 3, the work of the barium titanate-based capacitor as in Example 1 was fired. In this case as well, the generation of defective products was greatly reduced from 1% to 0.08% of the total when compared with the conventional case without a burnout agent, and the product yield was improved.

[0030]

According to the first or second aspect of the present invention, it is a coating agent capable of forming a reaction preventing layer having a micropore on the surface of a firing jig and improving the durability of the firing jig itself. It is possible to reduce the occurrence of defective products. According to claim 3 or claim 4, it is possible to manufacture a firing jig with improved durability and less generation of defective products, and the produced firing jig is also of good durability, and defective products of work are generated. Can be reduced.

The firing jig manufactured according to the present invention is
The space under the work is larger than that of the conventional product, and the contact area between the work and the reaction prevention layer is reduced. Therefore, by reducing the contact area between the work and the reaction preventive layer, there is an effect that the reaction between the firing jig base material component and the work component is made smaller than ever. The micropores formed on the surface of the firing jig can store various components that sublime and evaporate from the work, and the reaction between the deposition components of the above components and the work that occurs when the firing jig is used multiple times. It becomes possible to prevent fusion, and there is an effect that the number of times of use of the firing jig itself is greatly improved.

FIGS. 5 and 6 schematically show the operation and effect of the firing jig of the present invention. In the figure, the upper section shows the cross section when the work is first placed on the firing jig, and the lower section shows the cross section when the firing jig is repeatedly used. In the figure, reference numeral 4 is a work, reference numeral 5 is a reaction preventive layer obtained after firing a coating layer with a coating agent, and reference numeral 6 is deposition of components generated by sublimation and evaporation from the work when firing is repeated. It is a thing. As can be seen from the figure, even when the firing jig is used a plurality of times, the deposits generated from the work are less likely to come into direct contact with the work, and the durability against repeated use is improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a firing jig when wet and when a coating agent is applied according to an embodiment of the present invention.

FIG. 2 is a schematic view of a cross section of a firing jig when wet and dry when a coating agent with a small burn-off agent is applied in a comparative example of the present invention.

FIG. 3 is a schematic view of a cross section of a firing jig when wet and dry when a coating agent containing a large amount of burnout agent is applied in a comparative example of the present invention.

FIG. 4 is a schematic view of a cross section of a firing jig when the coating agent is applied to a firing jig base material when the coating agent that has been conventionally used does not include a burn-off agent, and when the coating material is wet and dry.

FIG. 5 is a schematic cross-sectional view of a firing jig and a work before and after repeatedly using the firing jig of the present invention. It is shown in an enlarged view.

FIG. 6 is a schematic cross-sectional view of a firing jig and a work before and after repeatedly using the firing jig in the conventional example. It is shown in an enlarged view.

FIG. 7 is a schematic cross-sectional view of an example in which a reaction preventing layer is formed on both surfaces of a plate-shaped firing jig.

[Explanation of symbols]

 1 Firing Jig Base Material 2 Coating Agent 3 Water-Absorbing Polymer 4 Workpiece 5 Reaction Prevention Layer 6 Deposit

Claims (5)

[Claims] 1. A composition for forming a coating layer on a surface of a firing jig for preventing a reaction with a work, comprising yttria,
A coating agent for a firing jig, which is mainly composed of zirconia or high-purity alumina containing a stabilizer such as calcia and a burnout agent. 2. A composition for forming a coating layer for preventing reaction with a work on the surface of a firing jig, which comprises yttria,
A coating agent for a firing jig, which comprises zirconia or a high-purity alumina containing a stabilizer such as calcia and a water-absorbing polymer as main components. 3. The coating agent according to claim 1 or 2 is applied to a firing jig base material selected from mullite, alumina, silicon carbide, cordierite, magnesia spinel, and the like, and the temperature is 1200 to 1600 ° C. A method for manufacturing a firing jig, which comprises firing under conditions. 4. A firing jig comprising a base material and a coating layer of the base material, wherein the base material is selected from mullite, alumina, silicon carbide and the like, and the coating layer has a diameter of 0.5 to 2 mm.
There is a hole on the entire surface, which is a burned-out trace, and the minimum coating thickness is 50-
A firing jig characterized by being a firing layer of a zirconia coating agent containing a stabilizer or a firing layer of a coating agent made of high-purity alumina, which secures 250 μm. 5. The firing jig according to claim 4, wherein firing layers of the coating agent are formed on both surfaces of the plate-shaped firing jig base material.