JPH0717461B2 - Aqueous ceramic binder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an aqueous ceramic binder, and more specifically,
The present invention relates to a water-soluble ceramic binder in which sludge has excellent defoaming properties and can be easily thickened when preparing a green sheet.

(Prior Art) Ceramic circuit boards are usually made of alumina, zirconia,
Ceramic powder such as aluminum silicate, titanium oxide, etc. is added to a solution containing a binder resin and a plasticizer, mixed and defoamed to prepare a slurry, which is then placed on a suitable support such as a polyester film. After coating and heating and drying, the support is peeled off to obtain a green sheet, which is then punched into an appropriate shape, and if necessary, printed with circuits, characters, etc., laminated and pressure bonded, and baked, It is manufactured by decomposing the binder.

As the binder resin in the ceramic binder, conventionally, a cellulosic resin such as ethyl cellulose,
Butyral resin such as polyvinyl butyral resin is used, and accordingly, as the solvent, an organic solvent that dissolves these is used. However, in recent years, from the viewpoint of environmental pollution and toxicity, ceramic binders have also been required to use water as a solvent.

As such an aqueous ceramic binder, conventionally,
It is known to use polyvinyl alcohol as a binder resin. However, when such a conventional aqueous ceramic binder is used, it is difficult for the mixture to defoam when a slurry is prepared from the mixture containing the ceramic powder, the binder resin and the plasticizer. In order to solve such a problem, a method of adding an antifoaming agent to the mixture is also adopted, but as the viscosity of the sludge increases, the effect of the antifoaming agent of lowering the surface tension is reduced, and eventually, The difficulty of defoaming when preparing sludge has not been fully resolved.

Further, it is known that the conventional aqueous ceramic binder as described above is blended with ethylene glycol as a plasticizer in order to enhance the handling property and post-processability of the obtained green sheet.

However, as the high integration of ceramic circuit boards progresses, the green sheets are shaped into a predetermined shape, and after printing a predetermined circuit on each, several to several tens are stacked and heat-sealed to integrate them. It is required to fire this into a hybrid circuit board.

The conventional water-based ceramic binder as described above is usually used without problems in the production of a ceramic circuit board for general use that does not require the heat-sealing property of the green sheet, but for the production of the hybrid circuit board. Is inferior in the heat fusion property of the green sheet and is not suitable for use.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned problems in the conventional aqueous ceramic binder, wherein the slurry is excellent in defoaming property during preparation of the green sheet, and is easy. It is an object of the present invention to provide a water-soluble ceramic binder that can be thickened to a desired level.

Further, it is an object of the present invention to provide an aqueous ceramic binder which gives the obtained green sheet excellent heat fusion property.

(Means for Solving the Problems) The aqueous ceramic binder according to the present invention contains a ceramic powder, a water-soluble polyvinyl acetal resin and a plasticizer as main components, and the solvent is a mixture of water and an alcohol having a boiling point of 100 ° C. or less. Is characterized in that.

The water-soluble polyvinyl acetal resin used as the binder resin in the present invention is obtained by reacting polyvinyl alcohol with an appropriate amount of an aldehyde in the presence of an acid catalyst. The degree of polymerization of polyvinyl alcohol used is
Those having a saponification degree of 300 to 2000 and a saponification degree of 75 to 99.8 mol% are preferable. Furthermore, regarding the acetalization degree, for example, the butyralization degree is 5 to 15 mol% and the acetoacetalization degree is
About 10 to 50 mol% is preferable. Further, even a resin acetalized with two or more kinds of aldehydes can be used as a binder resin in the present invention as long as it has water solubility.

In the ceramic binder according to the present invention, a mixture of water and alcohols having a boiling point of 100 ° C. or lower is used as a solvent. As such alcohols, for example,
Methyl alcohol (boiling point 63.9 ° C), ethyl alcohol (boiling point 78.7 ° C), isopropyl alcohol (boiling point 82.9)
℃) and the like.

As the ceramic powder, those conventionally known can be appropriately used. As such ceramic powder, for example, powder of alumina, zirconia, magnesia, sialon, spinel, mullite, crystallized glass, silicon carbide, silicon nitride, aluminum nitride, MgO-SiO ₂
-CaO based, B ₂ O ₃ -SiO _{2 system, PbO-B 2 O 3 -SiO} 2 system, CaO-SiO ₂
-MgO-B ₂ O ₃ system, PbO - may be mentioned glass frit, such as SiO ₂ -B ₂ O ₃ -CaO based.

As the plasticizer, those having good compatibility with the water-soluble polyvinyl acetal resin and having low volatility are practically suitable, and polyhydric alcohols having a boiling point of 230 ° C. or higher are preferably used. Examples of such polyhydric alcohols include diethylene glycol (boiling point 245 ° C), triethylene glycol (boiling point 278 ° C), glycerin (boiling point 290 ° C), hexamethylene glycol (boiling point 250 ° C) and the like. Of these, glycerin, which has an excellent plasticizing effect, is particularly preferably used.

The ceramic binder according to the present invention is a ceramic powder.
Generally, the polyvinyl acetal resin is used in an amount of 5 to 15 parts by weight with respect to 100 parts by weight, and the plasticizer is 1 part with respect to 100 parts by weight of the polyvinyl acetal resin.
It is used in an amount of 0 to 60 parts by weight, preferably 20 to 40 parts by weight. The amount of solvent water and alcohol is
It is not particularly limited, and the obtained sludge may have an appropriate kneading property, but it is usually used in the range of 50 to 200 parts by weight with respect to 100 parts by weight of the ceramic powder. The weight ratio of water to alcohol is 10:70 to 65:
A range of 15 is preferred.

The ceramic binder according to the present invention is used in the same manner as the conventional one, for example, for manufacturing a ceramic circuit board. That is, the ceramic powder is added to a water-alcohol solution containing a binder resin and a plasticizer, mixed and defoamed to prepare a slurry, which is coated on a support and dried by heating, and then the support is prepared. Peel to obtain a green sheet, then
This is punched into an appropriate shape, and if necessary, printed with a circuit, characters, etc., if necessary, a plurality of sheets are stacked, heat-fused to be integrated, and fired to obtain a hybrid circuit board. .

(Effect of the invention) Water and n-butyl alcohol (boiling point 117.7 ° C) as solvents
Does not improve the defoaming property. The reason is that defoaming property is not improved because water is preferentially volatilized in the process of mixing and thickening the ceramic powder, the binder resin, the plasticizer and the above solvent.

On the other hand, according to the present invention, when an alcohol having a boiling point of 100 ° C. or less is used as a solvent together with water, since this alcohol has a lower boiling point than water, it volatilizes preferentially over water. In addition to facilitating the volatilization of the solvent from the mixture, it also acts as a defoaming accelerator, and is therefore expected to have excellent defoaming properties.

When a water-soluble polyvinyl acetal resin is used as the binder resin, the flexibility of the green sheet is increased, but the heat fusion property is not improved even if the amount of ethylene glycol as the plasticizer is increased. The reason is that when the slurry is applied on the support and dried, ethylene glycol is volatilized with water by azeotrope, etc., and the amount on the surface of the green sheet is reduced. Will not be improved.

On the other hand, according to the present invention, when a glycol having a boiling point of 230 ° C. or higher is used as a plasticizer, the plasticizer remains effectively on the surface of the green sheet even during vacuum defoaming of the sludge and water drying. As a result, it seems that a green sheet having excellent heat-sealing property can be obtained.

Example 1 20 g of a water-soluble polyvinyl acetal resin (polymerization degree: 500, saponification degree: 88 mol%, butyralization degree: 10 mol%) was dissolved in a solution consisting of 80 g of water and 60 g of ethyl alcohol, and plasticized into the solution. As an agent, 4 g of glycerin (boiling point 290 ° C.) and 200 g of alumina powder were added and mixed in a ball mill for about 15 hours.

The resulting slurry is stirred and defoamed under a reduced pressure of 5 mmHg, while adjusting the viscosity to 10 poise, and then applied to a polyester film that has been subjected to release treatment to a thickness of about 0.5 mm,
After air-drying for 1 day, it was dried in a gear oven at 110 ° C. for about 3 hours to obtain a green sheet having a thickness of about 0.15 mm.

In the obtained green sheet, almost no dent due to the inclusion of air bubbles in the sludge was recognized.

Example 2 Except that a solution of 45 g of water and 95 g of ethyl alcohol was used as a solvent and 20 g of a water-soluble polyvinyl acetal resin (polymerization degree 800, saponification degree 95 mol%, butyralization degree 8 mol%) was used. A green sheet having a thickness of about 0.2 mm was obtained in the same manner as in Example 1.

In the obtained green sheet, almost no dent due to the inclusion of air bubbles in the sludge was recognized.

Example 3 A solution of 70 g of water and 70 g of methyl alcohol was used as a solvent, and a water-soluble polyvinyl acetal resin (polymerization degree 1800, saponification degree 88 mol%, acetoacetalization degree 15
Mol%) was used in the same manner as in Example 1 except that 20 g was used.
A green sheet having a thickness of about 0.2 mm was obtained.

In the obtained green sheet, almost no dent due to the inclusion of air bubbles in the sludge was recognized.

Example 4 The thickness was about the same as in Example 1 except that a solution consisting of 80 g of water and 60 g of isopropyl alcohol was used as the solvent.
A green sheet of 0.15 mm was obtained.

In the obtained green sheet, only a slight dent due to the inclusion of air bubbles in the sludge was recognized.

Comparative Example 1 Water-soluble polyvinyl acetal resin (degree of polymerization 50%) in 140 g of water
0 g, saponification degree 88 mol%, butyralization degree 10 mol%) 20 g is dissolved, and glycerin (boiling point 290
℃) 4g and alumina powder 200g are added, and ball mill
Mix for 15 hours.

When the obtained sludge was placed under a reduced pressure of 5 mmHg with stirring, a large number of bubbles were entrained in the sludge as the viscosity increased, and the bubbles remained even after returning to normal pressure.

When a green sheet was prepared using this sludge in the same manner as in Example 1, the obtained green sheet was
Many dents were observed due to the inclusion of bubbles in the sludge.

Comparative Example 2 A green sheet having a thickness of about 0.15 mm was obtained in the same manner as in Comparative Example 1 except that 4 g of ethylene glycol (boiling point 197 ° C.) was used as a plasticizer.

Many dents were found in the obtained green sheet due to the inclusion of bubbles in the sludge.

For each green sheet obtained as described above, the strength / elongation measurement, the heat fusion property measurement, and the surface state evaluation were performed. The results are shown in Table 1.

The test method is as follows.

Tensile strength measurement Punching from a green sheet with JIS K6301 No. 2 dumbbell to create a test piece (between marked lines 20 mm), 23 ° C overnight
After adjusting the condition at 50% RH, the tensile strength and breaking elongation were evaluated by measuring with an autograph at a tensile speed of 100 mm / min.

Heat fusion measurement 50 mm square test pieces were cut out from the green sheet, 10 sheets were piled up, 100 Kg / cm ² pressure was applied at 100 ° C., press molding was performed for 10 minutes, then split by hand and cut Visual observation was carried out. When the laminated surface was not visible, it was evaluated as ◯, and when it was clearly visible, it was evaluated as x.

Surface condition evaluation A 100 mm square test piece was cut out from the green sheet, and the condition of the dents on the surface was visually observed. In addition, in the evaluation, ◎ is almost concave, ○ is There were three dents, with slight dents and many dents.

Claims (1)

[Claims] 1. An aqueous ceramic binder containing a ceramic powder, a water-soluble polyvinyl acetal resin, and a plasticizer as main components, wherein the solvent is a mixture of water and an alcohol having a boiling point of 100 ° C. or less.