JPH02267175A - Preparation of ceramic sintered product - Google Patents

Abstract

PURPOSE:To prepare a porous ceramic sintered product having many fine pores by laminating a plurality of green sheets each comprising a ceramic powder and a resin powder and thereon having a pattern formed of an organic substance, heating the prepared laminate to eliminate the organic substance pattern and simultaneously sintering the laminate. CONSTITUTION:100 pts.wt. of a resin binder comprising 3-60 pts.wt. of a blocked isocyanate compound regenerating active isocyanate groups on heating, 100 pts.wt. of a polyurethane resin and 3-40 pts.wt. of a polyol is homogeneously mixed with 200-2000 pts.wt. of a ceramic such as alumina and formed into green sheets, on whose surfaces patterns are formed of an organic substance softening and decomposing at 150-250 deg.C to eliminate the organic substance patterns. The laminate is simultaneously sintered to remove the resin binder in the green sheet, thereby providing a porous ceramic sintered product having many fine penetrated pores.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a ceramic sintered body, and in particular,
The present invention relates to a method for manufacturing a porous ceramic sintered body having a large number of minute through-holes.

(Prior art) As a method for manufacturing this type of porous ceramic sintered body,
For example, a method is known in which a photosensitive resin pattern is embedded between green sheets, the photosensitive resin pattern is decomposed and disappeared by heating, the binder is removed from the green sheet, and the green sheet is fired (JP-A No. 63-99955). , No. 63-99956, No. 63-99957,
Publication No. 63-99958). In this method, a pattern is formed by exposing and developing a photosensitive resin, so the line width is 10 μm.
A large number of thin line patterns with a line spacing of about 20 μm (
It has the advantage of being able to form fine patterns) and has the potential to form minute through-holes.

The green sheet used in the above manufacturing method is made by bonding ceramic powder with a general organic binder.

On the other hand, a method for manufacturing a green sheet in which ceramic powder is bonded using a water-soluble polyurethane resin as a pinter has also been proposed (Japanese Patent Application Laid-Open No. 61-286261).

(Problems to be solved by the invention) The above-mentioned Japanese Patent Application Laid-Open No. 63-99955, No. 639995
Publication No. 6, Publication No. 63-99957, Publication No. 63-999
The manufacturing method disclosed in Publication No. 58 has the advantage of being able to form a fine line pattern as described above, but since the binder in the green sheet used is a general organic binder, it is difficult to form a fine line pattern. At the temperature at which the photosensitive resin starts to soften and decompose (usually 150 to 200°C), the organic binder in the green sheet also starts to soften and decompose at the same time. Therefore, as the photosensitive resin softens and changes in volume during decomposition (heat shrinkage), the green sheet binder that is in contact with the thin line pattern of the photosensitive resin flows together with the ceramic powder, and the thin line pattern disappears and is formed. There is a problem in that the pore walls collapse and the ceramic powder enters the pores, resulting in only a ceramic sintered body having incomplete pores containing sintering residue in the pores.

On the other hand, the green sheet disclosed in JP-A No. 61-286261 is produced using a water-soluble polyurethane resin instead of a normal organic binder, but the polyurethane resin used as the binder is a general thermoplastic resin. Since it is a polyurethane resin and is used alone, even if such a green sheet is used, the polyurethane resin flows during binder removal as described above, causing the pore walls to collapse, resulting in undesirable results. There was a problem in that only a ceramic sintered body having complete pores could be obtained.

The present invention has been made in view of the above-mentioned problems, and its purpose is to embed the organic pattern well in the green sheet when laminating the green sheet and the organic pattern, and to remove the binder from the green sheet. The object of the present invention is to provide a method for producing a ceramic sintered body that can form almost complete through-holes without sintering residue without causing collapse of the pore walls at times.

(Means for Solving the Problems) The method for manufacturing a ceramic sintered body of the present invention involves providing a pattern formed of an organic substance on the surface of a ceramic green sheet made of a resin binder and ceramic powder, and laminating a plurality of sheets. A method for producing a ceramic sintered body having pores by forming an organic pattern in a ceramic green sheet, heating the laminate to eliminate the organic pattern, and firing the laminate, the method comprising: The resin binder is characterized in that it contains a blocked isocyanate compound having an active isocyanate group that is regenerated when the laminate is heated, a polyurethane resin, and a polyol, thereby achieving the above object.

The present invention will be explained in detail below.

The ceramic green sheet used in the present invention contains a resin binder and ceramic powder, and may further contain additives such as a coloring agent, a solvent, etc., as necessary. The blending ratio of ceramic powder and resin binder is usually 200 to 2000 parts by weight of ceramic powder to 100 parts by weight of the total amount of resin binder. Green sheets can be prepared by conventional methods. For example, a predetermined amount of a resin binder is added to a mixture of ceramic powder and an organic solvent, and the mixture is kneaded uniformly. Obtained by supplying. In the present invention, the resin binder contains a blocked isocyanate compound having an active isocyanate group that can be regenerated by heating, a polyurethane resin, and a polyol.

Various pattern forming methods can be used to form the organic pattern on the surface of the green sheet. If a fine line pattern is not required, the desired pattern can be formed by dissolving a resin with good thermal decomposition in a solvent and using a screen printing method, etc. If a fine line pattern is required, a photosensitive resin film can be printed in green. A predetermined pattern may be formed by laminating the sheet onto a sheet, exposing it to light, and developing it. Any organic material may be selected as the organic material used for pattern formation, but it is preferable to use one that softens and decomposes at 150 to 250°C.

Layering multiple green sheets with patterns formed on them,
It is preferable to carry out thermocompression bonding after that. A conventional method such as hot pressing may be used for thermocompression bonding, and the thermocompression bonding temperature may be arbitrarily selected as long as it is lower than the active isocyanate group regeneration temperature of the blocked isocyanate compound, but is preferably 50°C to 150°C. °C range.

Next, the obtained laminate is heated to eliminate the organic pattern, and the laminate is fired to remove the binder. Here, in the debinding process of the laminate, the temperature is 25°C/
The temperature is gradually raised at a heating rate of less than 50 hr, and eventually the temperature reaches 50
It is preferable to hold the temperature at 0 to 600°C for a long time. In this case, in the temperature range where the resin binder contained in the green sheet causes a crosslinking reaction, it is particularly desirable to raise the temperature extremely slowly at a rate of 10°C/hr or less, and the temperature range is 120 to 200°C. It is desirable that The firing method after removing the binder is preferably a method in which the ceramic used is fired at 900 to 1650°C for 1 to 5 hours.

In this way, the portions of the pattern where the organic material pattern disappears become pores, and a ceramic sintered body having a large number of pores is obtained.

Next, the blocked isocyanate compound, polyurethane resin, and polyol contained in the resin binder will be explained in more detail.

A blocked isocyanate compound is produced by blocking the isocyanate groups of a polyisocyanate having two or more active isocyanate groups in the molecule with a blocking agent.
The active isocyanate group is temporarily deactivated. The regeneration temperature of the active incyaneto group can be adjusted by changing the type of blocking agent, and is arbitrarily set in a higher temperature range than the thermocompression bonding temperature of the green sheet, and is preferably set to, for example, 60° C. or higher. At temperatures below 60°C, the reactivity of the isocyanate group is extremely low. The blocked isocyanate compound is preferably a polyisocyanate containing 1.0 mmol/g or more of active isocyanate groups in its molecule, with the isocyanate groups blocked with a blocking agent.

Examples of the polyisocyanate include triresin diisocyanate, diphenylmethane diisocyanate,
Hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, modified substances thereof, etc. are preferably used, and as the blocking agent to temporarily inactivate the active isocyanate group, For example, phenols such as phenol and nitrophenol, alcohols such as methanol and ethanol, and oximes such as acetaldoxime and methyl ethyl ketoxime are preferably used. The blocking agent is an active hydrogen compound and reacts with the isocyanate group to lower the thermocompression bonding temperature of the green sheet (
The compound is not limited to the above compounds as long as it produces a stable addition compound with low reactivity at temperatures below 60°C.

The above-mentioned polyurethane resin is used as a resin binder for the green sheet together with the blocked isocyanate compound and polyol, and it is preferable that the polyurethane resin has the ability to form a green sheet even if the flocked isocyanate compound and polyol are in an unreacted state. Also, it is preferable to have softening fluidity during thermocompression bonding. In particular, the number average molecular weight of the polyurethane resin is preferably 104 to 106, and the number average molecular weight of the polyurethane resin is preferably 0.01 to 1.0 mmol.
/g, more preferably 0.0
It is 2 to 0.5 mmol/g. If the number average molecular weight of the polyurethane resin is smaller than the above range, the ability to form a sheet will be reduced. That is, when forming a green sheet, the sheet contains a large amount of ceramic powder relative to the resin binder, so if the number average molecular weight of the polyurethane resin is small, the mechanical strength of the sheet tends to decrease. Furthermore, if the number average molecular weight of the polyurethane resin is too large, the solvent solubility will decrease. Note that the above number average molecular weight is a value determined by GPC analysis. Further, the polyurethane resin that can be used is not limited to a number average molecular weight within the above range, and may be outside this range as long as the mechanical strength of the sheet is acceptable. In addition, if the amount of active hydroxyl groups contained in the polyurethane resin is too small, the reactivity with isocyanate compounds will be poor, crosslinking will not proceed sufficiently during heating, resulting in lack of heat resistance, collapse of pore walls, and If the amount is too large, the crosslinking reaction will proceed excessively, resulting in extremely brittle pore walls that are likely to collapse. Examples of the components constituting the main chain of the polyurethane resin include polyester, polyether, epoxy, acrylic, etc., but polyester is preferable from the viewpoint of heat resistance.

The above polyol has 0.1 to 20 m of active hydroxyl groups in the molecule.
It is preferable to contain mol/g, more preferably 0
．． 5~lommol/g. Examples of such polyols include polyester polyols such as polyethylene adipate, polyhexamethylene adipate, and polycaprolactone, polyether polyols such as polyoxypropylene diol, polytetramethylene glycol ether, and polyoxyethylene diol, epoxy polyols, and acrylic polyols. etc. can be mentioned. Among these, polyester polyols are particularly preferably used in terms of heat resistance.

When the amount of active hydroxyl groups contained in the polyol decreases,
When heated, the crosslinking density with isocyanate groups decreases, heat resistance becomes insufficient, and the pore walls tend to collapse.On the other hand, when the amount increases, the pore walls become brittle and collapse easily.

The blending ratio of each of the above components is preferably 3 to 40 parts by weight of the polyol and 3 to 60 parts by weight of the blocked isocyanate compound to 100 parts by weight of the polyurethane resin, and within this range, the blending ratio can be changed arbitrarily. It is possible to adjust the fluidity of the binder when pressing the green sheet. If the amount of the polyol and proxisocyano compound in the polyurethane resin is less than the above range,
There is a risk that residue may remain in the pores. That is, if the amount of polyol blended is too small, crosslinking with isocyanate will not be sufficiently performed during debinding, and the effect of binding and holding the ceramic powder will be reduced. Furthermore, if the blending amount of the polyurethane resin is too small, the green sheet forming ability tends to decrease, the handleability of the green sheet decreases, and sintering residues may remain in the pores.

When a pattern of an organic material is formed on the surface of a green sheet prepared using a resin binder having the above composition, and a plurality of green sheets are laminated and thermocompression bonded, at this thermocompression bonding stage, the isocyanate of the block isocyanate compound of the binder is Since the groups remain inactivated and do not undergo a crosslinking reaction, the green sheets have favorable fluidity, and a pattern of organic material can be satisfactorily embedded between the green sheets. The fluidity of this binder can be freely adjusted by changing the composition of the resin binder, that is, the type and/or mixing ratio of the polyurethane resin, polyol, and blocked isocyanate compound. You can choose freely compared to binders.

In addition, the thermocompression-bonded laminate was supplied to a heating furnace at 10℃/
When the temperature is gradually raised to the debinding treatment temperature at a heating rate of hr or less, the active hydroxyl groups of the polyol and polyurethane resin and the isocyanate groups of the blocked isocyanate compound react, and the binder forms a three-dimensional network structure, The resin has excellent heat resistance. Therefore, at the point when the organic material of the pattern starts to soften and decompose, the binder does not cause softening and flow and holds the ceramic powder together, so the pore walls do not collapse as the pattern volume decreases. . Therefore, by further firing at elevated temperature after removing the binder, a ceramic sintered body containing no sintering residue and having complete through-holes can be obtained.

(Example) The invention will now be described with reference to examples.

Alumina powder (average particle size 2 μm) 230 Glass frit powder (MgO-3102-CaO system, average particle size 0.8 μm) 12 Black colorant (Solvent Black 7)
1.5 methyl ethyl ketone
140 The above mixture and a predetermined amount of resin binder shown in Table 1 below were supplied to an alumina ball mill and kneaded for 3 hours to obtain a slurry. This slurry was supplied to a doctor blade type green sheet making machine, coated and dried on a polyethylene terephthalate film, and then
A green sheet with a size of 100 mm was prepared.

The obtained green sheet and photosensitive resin film (dry film resist "Photowell" manufactured by Tsukisui Kagaku Kogyo ■)
A 25 μm thick support film (polyethylene terephthalate) was thermally laminated, a negative photomask with a fine line pattern was adhered to the support film of a photosensitive resin film, and a 40 mJ/cm2 ultraviolet ray was exposed at a distance of 50 cm from a 3 kW high-pressure mercury lamp. . Next, the supporting film of the photosensitive resin film was peeled off, and development was performed by spraying 1 kg/cm2 of 1 wt% aqueous solution of sodium carbonate at 30°C to form a fine line pattern with a line width of 25 μm and a line spacing of 25 μm on the surface of the green sheet. did.

The support film was peeled off from the green sheet on which the thin line pattern was formed, and 500 sheets were laminated at 80°C for 30 minutes.
Press for 1 minute at 0 kg/cm2, 120X
A 120 x 20 mm laminate was prepared, and this laminate was sliced perpendicular to the laminated surface to obtain a 3 mm thick slice.

The obtained sliced body was placed in a heating furnace and heated at a heating rate of 5°C/hr, held at 180°C for 5 hours to harden the green sheet binder, and then heated at 10°C/hr.
The temperature was raised at a heating rate of 200°C/hr, and held at 500°C for 5 hours to eliminate the fine line pattern of the photosensitive resin and remove the binder.
By firing at 650'C for 2 hours, a porous ceramic sintered body having a large number of independent pores on the face opposite to the - face was obtained.

Table 1 shows the results of observing the cross section of the pores in this porous ceramic sintered body using a scanning electron microscope.

The mixture used in Example 1 and a predetermined amount of the green sheet binder shown in Table 1 below were mixed in an alumina ball mill for 30 minutes.
A slurry was obtained by kneading for a period of time, and thereafter a porous ceramic sintered body was obtained in the same manner as in Example 1. The results of observing the pore cross section of this ceramic sintered body with a scanning electron microscope are also shown in Table 1 below.

(Margins below) \ Examples and Comparative Examples (Note 1) P-U is a polyurethane resin (manufactured by Japan Polyurethane Industry Co., Ltd., trade name "Niraporan 2301J") with a molecular weight of 50,000 and a solid content of 40%.

(Note 2) P-0)1 is hydroxyl group f13.8 mm o l
/ solid content 1g, solid content 100% polyol resin (trade name "Niraporan 1100J").

(Note 3) B-1c has an effective isocyanate group amount of 3.5 mm
.

It is a blocked isocyanate compound (trade name: "Coronate 2507J") with a solid content of 1 g and a solid content of 80%.

As shown in Table 1 above, in Examples 1 and 2, ceramic sintered bodies containing no sintering residue and having completely through holes of 25 μm were obtained.

On the other hand, in Comparative Examples 1 and 2, part of the pore walls collapsed during binder removal and firing, and through holes were not formed.

Polyvinyl butyral resin was used as a binder instead of the green sheet binder shown in Table 1 used in Takumi Shiomoji Example 1, and the blending amount was 30 parts by weight of polyvinyl butyral resin to 230 parts by weight of alumina powder. A porous ceramic sintered body was obtained in the same manner as in Example 1 except for this.

When the pores of this ceramic sintered body were observed with a scanning electron microscope, no through pores were formed due to the collapse of the pore walls during binder removal and firing.

(Effects of the Invention) The present invention prevents the collapse of the pore walls and removes sintering residues when removing the binder by heating a laminate in which green sheets on which patterns of organic materials are formed are removed. It has the effect of efficiently manufacturing ceramic sintered bodies with through-holes of various sizes and shapes, and is useful for manufacturing parts and devices made of ceramic sintered bodies that require through-holes, such as inkjet nozzles and ceramic filters. It is extremely suitable for

that's all

Claims (1)

[Claims] 1. A pattern formed of an organic substance is provided on the surface of a ceramic green sheet made of a resin binder and ceramic powder, a plurality of these sheets are stacked, the organic pattern is embedded in the ceramic green sheet, and the laminate is heated to form the organic pattern. A method for manufacturing a ceramic sintered body having pores by burning the laminate and eliminating the pores, wherein the resin binder is a blocked isocyanate compound having an active isocyanate group that is regenerated when the laminate is heated. , a polyurethane resin, and a polyol.