JPH0140728B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method and apparatus for manufacturing ceramic slips into green sheets. [Prior art] Conventionally, when producing green sheets using ceramic slips, the dispersed phase of the slips was several micrometers thick.
Because the film is composed of particles with a particle size of about Cracks, undulations, warping, etc. were less likely to occur in the green sheet. On the other hand, one of the present applicants prepared a colloid containing one or more kinds of inorganic substances as a dispersed phase and water as a dispersion medium as a method for producing ceramic green molded bodies, and if necessary, added hydrophilic organic After adding and mixing a molecular binder, the dispersion medium is removed to the extent that a portion of the dispersion medium remains to form a gel, and this gel is used to produce ceramic green molded bodies of various shapes. (Tokuko Sho 63-48823, Sho 63-48824, Sho 63
−43337). [Problems to be Solved by the Invention] The particles of the dispersed phase of this colloid have a diameter of several tens of angstroms or less, which is less than 1/100 of the particle diameter of the dispersed phase of conventional slips.
Because the colloid has a particle size of several thousand angstroms, when this colloid is used as a slip for producing ceramic green sheets, and when an aqueous dispersion system or a non-aqueous dispersion system such as alcohol is used as the dispersion medium, it is difficult to absorb the particles adsorbed onto the molecular surface. The amount of these dispersion media tends to increase compared to conventional raw materials. Therefore, if a film is formed using the above colloid and then dried using a conventional drying method using external heating such as hot air drying,
The drying shrinkage rate that occurs when the water or alcohol adsorbed on the raw material evaporates increases, and the green sheet tends to crack, undulate, warp, etc. after drying. Therefore, when drying this type of slip after film formation by heating, it is necessary to dry it under atmospheric pressure.
Since it is necessary to leave the product at a temperature slightly higher than room temperature for a long time, it has been desired to shorten the drying time. The present invention satisfies the above-mentioned needs by drying the film-formed ceramic slip in a shorter time than the conventional drying time, and producing ceramic green sheets without defects such as cracks, waviness, and warping with fewer man-hours. The purpose of the present invention is to provide a method and apparatus for doing so. [Means for Solving the Problems] The ceramic green sheet of the present invention is manufactured by a continuous process. The feature of the first invention is that a ceramic slip using a liquid having hydroxyl groups as a dispersion medium is applied to a carrier film with a coating thickness of 1 mm to 3 mm using a doctor blade.
A film-forming process in which a film is continuously coated in a range of mm, and immediately after this film-forming process, the coated film is subjected to microwave drying in one or more drying chambers together with the carrier film. The coated film is irradiated with microwaves having an energy density in the range of 1KW to 2KW ^per square meter of coated film area in the drying chamber, and at the same time the drying chamber is heated to a predetermined temperature and temperature. The method of manufacturing a ceramic green sheet includes a drying step of heating and drying the coating film to form a ceramic green sheet by supplying and discharging hot air whose humidity is adjusted at a predetermined rate. Further, the second invention of the present application is characterized by a film forming machine that continuously coats a carrier film with a ceramic slip using a liquid having hydroxyl groups as a dispersion medium to form a film using a doctor blade; a microwave dryer comprising one or more drying chambers, which irradiates the coated film with microwaves having an energy density of 1KW to 2KW ^{per square} meter of coated film area; Ceramics green sheet manufacturing equipment installed in a room and equipped with a humidity controller that adjusts warm air to a predetermined temperature and humidity, and a supply/discharge device that supplies and discharges the humidity-controlled warm air at a predetermined speed. It is in. In addition, the ceramic slip in the above manufacturing method is preferably a slip prepared by hydrolyzing one or more types of alkoxide, and in particular, the ceramic slip prepared by hydrolyzing one or more types of alkoxide, and in particular, the particle size of the dispersed particles is from several tens of angstroms to several thousand of angstroms.
It is desirable that the value be within the range of . In addition, in order to manufacture ceramic green sheets through a continuous process, in addition to adjusting the microwave energy density of the microwave dryer to a predetermined density, we also adjust the humidity inside the dryer to a predetermined humidity and It is necessary to rectify the air flow in order to obtain a green sheet that is completely free from defects such as cracks, undulations, and warpage. In this specification, "alkoxide" refers to a compound in which the hydrogen atom of the OH group of an alcohol is replaced with a metal atom. The slip used for manufacturing the ceramic green sheet of the present invention uses water as a dispersion medium and has a thickness of several μm.
Needless to say, conventionally used slips having inorganic particles having a particle size of about 100% as a dispersed phase can be applied, and any slip using a dispersion medium having a hydroxyl group such as alcohol other than water can be applied. Particularly suitable is an inorganic colloid in which the main dispersed particles have a particle size of several tens of angstroms to several thousand of angstroms. When this colloid is used as a slip, the dispersed phase of the colloid is not particularly limited as long as it is inorganic, such as Al,
Examples include metal or nonmetal oxides, hydroxides, or hydrated compounds thereof such as Mg, Ti, Ba, B, Pb, Zn, Zr, and Be, and mixtures thereof may be used. In this case, the inorganic substance may be a substance obtained by hydrolyzing one or more types of alkoxides. For example, a colloid using this inorganic substance may be a substance obtained by hydrolyzing aluminum isopropoxide [Al(C ₃ H ₇ O) ₃ ]. Decomposes to generate boehmite [AlOOH],
A stable pseudo-boehmite sol can be obtained by adding a small amount of hydrochloric acid to peptize the sol.
Since this pseudo-boehmite sol is a colloid, the particle size is uniform, and since aluminum alkoxide is used, a highly pure raw material can be easily obtained. Furthermore, it is preferable to add an organic polymer binder to the colloid to obtain a slip having a solid content of 10% by weight or more, from the viewpoint of the drying rate and drying shrinkage rate of the slip after film formation. In this case, the critical moisture content of the slip is approximately 400%. The method for forming the ceramic slip is to use a carrier film as a moving carrier, and to form a film by continuously applying the slip onto the carrier film with a doctor blade to a coating thickness of 1 mm to 3 mm. A coating method is used. If the coating thickness is less than 1 mm, the strength of the dried green sheet will not be sufficient and it will break easily, and if it exceeds 3 mm, the drying time will be prolonged, so the coating should be within the above range. Furthermore, as the carrier film material, a material that does not absorb microwaves is used to reduce the occurrence of misalignment and wrinkles in the ceramic sheet due to contraction or expansion due to microwave absorption and heat generation. Considering this point, polyethylene and
Organic polymer films such as polyester, polypropylene, and fluororesin are preferred. The coating film of the ceramic slip is introduced into and passed through a microwave dryer provided in the transport path of the carrier film, so that it is heated and dried subsequent to film formation. In this case, the frequency of the microwave can be arbitrarily selected from the range of 900 to 20,000 MHz, but preferably 2,450 MHz or 915 MHz, which are mainly used for high frequency dielectric heating. Further, the drying time can be shortened by increasing the penetration depth of the microwave of the present invention into the slip to about 2.5 to 6.5 cm so that internal heating can be instantaneously carried out from the surface of the coating film to the interface of the carrier film. In addition, when the coating film is dried in the microwave dryer to become a ceramic green sheet, the temperature, humidity, and air flow inside the dryer must be controlled to completely prevent cracks, warping, and waviness of the green sheet. Adjustment is necessary. In this case, temperature adjustment is performed by controlling the energy density of microwaves, and humidity adjustment and air flow adjustment are performed by using a humidity controller that adjusts warm air to a predetermined temperature and humidity in a dryer, and a humidity controller that adjusts warm air to a predetermined temperature and humidity. This is done by installing a supply/discharge machine that supplies and discharges air at a predetermined speed. Here, the hot air temperature is selected from a range of 50 to 80°C, the relative humidity of the hot air is selected from a range of 50 to 90%, and the hot air supply/discharge speed is desirably 100 cm/sec or less. In addition, the energy density of the microwave or the transport speed of the carrier film is adjusted so that the evaporation rate of the dispersion medium from the surface of the coating film in the dryer and the movement rate of the dispersion medium within the coating film are the same. This is preferable in order to prevent the formation of a dry film on the surface of the coating film and to prevent the formation of cracks. When the slip of the present invention is formed to a coating thickness of 1 to 3 mm, the energy density of the microwave irradiated is adjusted within the range of 1 to 2 KW per 1 m ² of coating area.
If the energy density is less than 1KW, the drying time will be longer, and if it exceeds 2KW, defects in the coating film (cracks, etc.) may occur.
Since warping and waviness are likely to occur, irradiation is performed within the above range. Further, it is preferable to suppress the evaporation rate of the dispersion medium to 1 kg/m ² ·hr or less in order to prevent the formation of a dry film on the surface of the coating film and to prevent the formation of cracks. In addition, if the coating width of the slip is large and it is necessary to increase the effective drying length of the microwave dryer, divide the dryer into two or more drying chambers, equip each drying chamber with a microwave oscillator, and It is better to reduce the degree of dryness the further you go to the drying room. When a dryer is partitioned into a plurality of drying chambers, it is effective to have a structure in which the drying chambers are divided in order to prevent microwave interference between the drying chambers. Finally, the ceramic green sheet sent out from the microwave dryer is separated from the carrier during film formation, and is either wound up or sent as a sheet to the next secondary forming process or firing process depending on the purpose of the final product. sent to. [Example] Next, an example of the present invention will be described in detail based on the drawings. As shown in FIG. 1, an endless belt 10 is provided around a driving roll 11 and a driven roll 12. A carrier film 13, which is a moving carrier, is transferred onto the belt 10 by a take-up roll 14 and a delivery roll 15 at the same speed as the belt 10. In this example, film 13 is a polyester film. A film forming machine 17 is disposed on the belt 10 near the driven roll 12. This film forming machine 17 consists of a slip storage tank 18 and a doctor blade 19. A microwave dryer 20 having a total length of about 25 m is disposed in the carrier film 13 transfer path behind the doctor blade 19. This dryer 20 is
Microwave oscillator 2 with built-in magnetron 21
2, an isolator 23, a matching box 24, and an oven-type drying chamber 25, each of which is connected via a waveguide 26. This waveguide 26 has two
It is branched into two parts and connected to a drying chamber 25. The microwave oscillator 22 is connected to a control device (not shown), and is configured so that its microwave energy density can be set arbitrarily. An air supply pipe 28 of a supply/discharge device (not shown) is connected to the outlet side of the drying chamber 25, and an exhaust pipe 29 thereof is connected to the inlet side. connected to. This humidifier 30
In order to maintain the humidity in the drying chamber 25 at a predetermined level, the system detects the humidity of the air in the drying chamber 25 discharged from the exhaust pipe 29 and automatically adjusts the humidity of the air sent into the air supply pipe 28. It is configured so that the exhaust air speed from the exhaust pipe 29 can be adjusted and arbitrarily set. 31 is an air supply port, and 32 is an exhaust port, which communicates with the atmosphere. Further, a peeling roll 33 is provided after the drying chamber 25, and a green sheet take-up roll 34 is provided above the drive roll 11. A method for manufacturing ceramic green sheets using an apparatus having such a configuration will be described. The ceramic slip A used here was obtained by the following method. First, add 100 mol of water to 1 mol of aluminum isopropoxide, and make about 80 mol of water.
Hydrolyzed at ℃ for 30 min to produce boehmite,
This was peptized by adding a small amount of hydrochloric acid to obtain a pseudo-boehmite sol (AlOOH). Next, polyvinyl alcohol as a hydrophilic organic binder and 3-methylpentane-1,3,5-triol (hereinafter referred to as Petriol) as a plasticizer were added to this pseudo-boehmite sol in a weight ratio of AlOOH:PVA:Petriol=1.00. :0.33：
They were each added at a ratio of 0.33, stirred and dissolved at 80°C, and the solid content was adjusted to 10% to form a ceramic slip. This ceramic slip A was poured into a slip storage tank 18 and coated with a doctor blade 19 onto a polyester carrier film 13 having a width of 200 mm. The coating width of the slip A on this film 13 was 150 mm, and the coating thickness was 2 mm. The carrier film 13 coated with this slip A is attached to the belt 1.
Microwave dryer 20 at the same speed of 15cm/min as 0.
was introduced into the drying chamber 25 and passed through. The microwave dryer 20 adjusts the energy density of 2450 MHz microwave to 1.0 KW output per 1 m ² of coating area, and the humidity controller 30 blows air with a relative humidity of 60% from the air supply pipe 28 at a rate of 30 cm/sec. By sending it into the drying chamber at wind speed and discharging it from the exhaust pipe 29,
Ceramics green sheet B was obtained after a drying time of about 3 hours. Although the thickness of this ceramic green sheet B was reduced from 2 mm before drying to 0.2 mm, there were no defects as a green sheet such as cracks, warping, and waviness, and it was flexible with a moisture content of 20%. In this state, the green sheet was peeled off from the carrier film 13 by a peeling roll 33 and wound up on a green sheet winding roll 34. FIG. 2 shows another embodiment of the present invention.
A set of microwave dryers 20 are installed in series. The total length of the six sets of microwave dryers 20 is approximately 25 m. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same components. An example of manufacturing a ceramic green sheet using an apparatus having such a configuration will be described. The same ceramic slip A as in the previous example was applied onto a carrier film 13 having a width of 500 mm using the same film forming machine 17 as in the previous example. At this time, the coating width of the slip A on the film 13 was 440 mm, and the coating thickness was 2 mm. This carrier film 13 is 30
Microwave dryer 2 with 6 sets at a speed of cm/min
0 into the drying chamber 25. The microwave of each microwave dryer 20 used a frequency of 2450 MHz, and the microwave oscillator 22 and humidity controller 30 were adjusted to the conditions shown in the following table for drying.

[Table] As a result, ceramic green sheet B was obtained in an extremely short drying time of about 1 hour and 30 minutes. This ceramic green sheet B was thinned to a thickness of 0.2 mm in the same manner as in the above example, but there were cracks and
There are no defects as a green sheet such as warping or waviness, and it is in a flexible state with a moisture content of 20%.
The green sheet was peeled off from the carrier film 13 by a peeling roll 33 and wound up on a green sheet winding roll 34. [Effects of the Invention] As described above, according to the present invention, immediately after a ceramic slip using water or alcohol having a hydroxyl group as a dispersion medium is formed using a film forming machine using a doctor blade, a carrier film is formed. By continuously drying using internal heating in a microwave dryer placed in the transfer path, ceramic green sheets manufactured from slips whose main constituents are colloidal ceramic particles can also be molded after drying. It has the excellent effect of eliminating defects such as cracks, warping, and waviness that have conventionally been observed in sheets, and also shortening the manufacturing period of ceramic green sheets by quickly drying them with fewer man-hours.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a ceramic green sheet manufacturing apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram of a ceramic green sheet manufacturing apparatus according to a second embodiment of the present invention. A: Ceramic slip, B: Ceramic green sheet, 10: Endless belt, 1
3: Carrier film, 17: Film forming machine, 19: Doctor blade, 20: Microwave dryer, 2
1: Magnetron, 22: Microwave oscillator, 2
3: Isolator, 24: Matching device, 25: Drying room, 26: Waveguide, 30: Humidity controller, 33: Peeling roll, 34: Green sheet winding roll.

Claims (1)

[Scope of Claims] 1. A film forming process in which a ceramic slip using a liquid having hydroxyl groups as a dispersion medium is continuously applied to a carrier film with a coating thickness of 1 mm to 3 mm using a doctor blade; Immediately after the film forming step, the coating film is introduced together with the carrier film into a microwave dryer consisting of one or two or more drying chambers, and passed through it,
In the drying room, the coating film area is 1 m ² for the coating film.
The coating film is heated by irradiating microwaves with an energy density in the range of 1KW to 2KW per unit, and at the same time supplying and discharging warm air adjusted to a predetermined temperature and humidity into the drying chamber at a predetermined speed. A method for producing a ceramic green sheet, including a drying step of drying and forming a ceramic green sheet. 2. The method for producing a ceramic green sheet according to claim 1, wherein the ceramic slip is prepared by hydrolyzing one or more alkoxides. 3. A film forming machine that continuously coats a carrier film with a ceramic slip using a liquid having hydroxyl groups as a dispersion medium using a doctor blade to form a film; a microwave dryer which irradiates the coating film with microwaves with an energy density ranging from 1KW to 2KW ^per square meter of coating film area; A ceramic green sheet manufacturing device equipped with a humidity controller that adjusts temperature and humidity to a predetermined temperature and a supply/discharge device that supplies and discharges humidity-controlled warm air at a predetermined speed.