JPS6241190B2 - - Google Patents

Description

[Detailed description of the invention]

Polyvinyl alcohol (hereinafter referred to as PVA)
is widely known as a binder for ceramic raw powder (hereinafter referred to as raw material powder), and its excellent film-forming properties and low wettability to metals are particularly useful for granulation by spray drying and mold release in mold press molding. Due to its remarkable effectiveness, boron, including boric acid, boron oxide, and aluminum borate, has been particularly effective as a binder for slurry of raw material powder that is spray-dried for the purpose of mold press molding. It could not be used for raw material powders containing compounds. These boron compounds are used when coloring pigments are blended into raw material powder to blacken or brown ceramics for light shielding, such as ceramic packages for ICs.
Although it is used to make the color tone uniform, boron compounds react with PVA in the slurry and gel it, impairing its function as a binder, so it is unavoidable for raw material powders containing boron compounds.
It was necessary to select a binder other than PVA. The present invention provides a binder for raw material powder containing a boron compound that has excellent film-forming properties during spray drying and high mold releasability during mold press molding.
This allows the use of PVA, and the boron compound in the raw material powder is dissolved in alcohol that is sparingly soluble in water, such as n-octyl alcohol, n-butyl alcohol, isoamyl alcohol, and isobutyl alcohol. An aqueous solution (W) of a surfactant is added and emulsified to produce an (O-W) emulsion, and the emulsion is mixed with the above raw material powder excluding the boron compound and an aqueous solution of PVA to form a slurry. Organic solvents in which boron compounds such as boric acid have an OH group,
In particular, we focused on dissolving in alcohol, and by emulsifying and dispersing a solution of the boron compound in water with alcohol that is poorly soluble in water,
The molecular layer of the emulsifier on the surface of the alcohol particles prevents direct contact between the boron compound and the surrounding PVA molecules, completely preventing gelation of the PVA particles, and preventing the boron compound from forming a slurry-like raw material powder.
We succeeded in making it possible to add PVA. Example 1 50 c.c. of n-butyl alcohol in which 0.2 g of boric acid was dissolved was added to 80 c.c. of water and 0.2 g of a nonionic surfactant (Nonion E-230, HLB value 17.3, NOF) aqueous solution. 5g of PVA, which is considered to be the upper limit as a binder, is added to this emulsion. Even when dissolved, PVA does not gel at all, and is left at room temperature for 80 hours.
However, it remained stable even if left alone.
In a comparative product in which n-butyl alcohol was replaced with water-soluble ethyl alcohol, and other conditions were the same, PVA began to gel immediately after dissolution, and after 5 minutes, it completely gelled, showing that water and the poorly soluble alcohol were responsible. The effect was seen. Example 2 Contains 0.1% boron oxide as final product
98%Al ₂ O ₃ -0.4%SiO2 _-0.4 %CaO-1.1%MgO-
For a composition consisting of 0.1% B ₂ O ₃ (A) 1.8 g of boric acid (H ₃ BO ₃ Hayashi Pure Chemical Reagent Grade 1)
(equivalent to 1 g of B ₂ O ₃ ) was dissolved in 112 g of n-octyl alcohol, which is sparingly soluble in water, using a magnetic stirrer to obtain a solution O, which was then mixed with a nonionic surfactant (Nonion E-230HLB value 17.3). The O-W emulsion mentioned above is prepared by mixing 0.6 g of fat and oil dissolved in 300 c.c. (W) of water using a propeller stirrer. (B) Alumina (Showa Light Metal AL-160SG) 980g Silicic anhydride (Tomita Pharmaceutical Micom F) 4g Calcium carbonate (Yoneyama Pharmaceutical Reagent 1st grade) 4g Magnesium carbonate (Katayama Chemical Reagent 1st grade) 11g and Microsol (peptizer compatible) Mix 5g of Kagaku Kogyo KE-412 special carboxylic acid) and 5g of polyethylene glycol (plasticizer Sanyo Chemical PEG-4000S). (C) Dissolve PVA Denka B-17 in 200 c.c. of water. When the above three materials (A), (B), and (C) were ground and mixed for 15 hours using an alumina magnetic ball with an internal volume of 3, no gelation of PVA was observed and it was normal. The gas temperature was 190℃,
Spray drying was carried out under the conditions of a disk diameter of 110 mmφ and 7200 RPM to obtain granules with an average particle size of about 50 μm. Separately, the binder PVA was replaced with a water-soluble acrylic resin (Nippon Pure Chemical Industries AT-51DL), which is completely unaffected by boron compounds, and granules with an average particle size of approximately 53μ were used as a comparative product under the same conditions. Granulate,
Both granules were formed into a size of 40 x 12 x 5 mm using a mold press at a pressure of 1500 kg/cm ² and then placed in an electric furnace.
Table 1 shows the results of comparing various properties after firing at 1570°C for 1 hour.

[Table] However, the number of times that the mold can be used continuously is the number of times that the mold can be press-molded continuously after cleaning it until the next cleaning. As is clear from the above table, the slurry obtained by the present invention exhibits low viscosity with good fluidity;
Granules produced by spray drying are superior to comparative products in terms of mold releasability as expressed by the number of times the mold can be used continuously, and the transverse rupture strength of the unsintered body press-molded with a mold, especially in the former mold releasability. The reason for this is that the boron compound exhibits a much higher value compared to other products, and there is no particular difference in the sintered product.The reason why the boron compound is made into an emulsion as described above prevents contact with PVA, and the reaction between the two prevents the PVA from coming into contact with the boron compound. Prevents the gel value of
It is clear that this is due to the fact that PVA's original excellent properties are exhibited as is, and the present invention has great industrial value as it has made it possible to blend PVA into raw material powder containing boron compounds, which was previously considered difficult. It is. The above explanation is based on the case of press molding using granules granulated by spray drying as the most effective method, but when used in a slurry state such as casting molding or doctor blade method. It can be applied to 〓〓〓〓〓

Claims (1)

[Claims] 1 O-W emulsion made by dissolving a boron compound in an alcohol that is sparingly soluble in water and then adding it to an aqueous surfactant solution to emulsify it (where O is a combination of a boron compound and an alcohol that is sparingly soluble in water). 1. A method for preparing a ceramic raw material containing a boron compound, which comprises mixing an inorganic raw material powder and an aqueous solution of polyvinyl alcohol to form a slurry.