JPH01153515A - Method for granulating magnesium oxide raw material for forming - Google Patents

Abstract

PURPOSE:To efficiently granulate an MgO raw material for forming under safe working environment at a low cost by primarily granulating MgO powder with a binder solution containing a surfactant using a stirring and mixing method and providing uniform grain size by a disintegrating method. CONSTITUTION:A magnesium oxide raw material for forming is pulverized into fine powder, which is then placed in a mixer, stirred and mixed with a binder solution (e.g., a solution of polyvinyl butyral in ethanol) containing a surfactant (e.g., polyethylene glycol monooleate) to carry out primary granulation. The resultant primarily granulated substance is subsequently placed in a disintegrating granulator, disintegrated with a disintegrating tool and passed through a screen to make grain size uniform and afford granulated grains of the magnesium oxide. The granulated grains have high fluidity due to a powder having uniform grain size distribution and are preferably used as a raw material powder for forming magnesium oxide formed products requiring high characteristics, such as sheaths for calcining electronic or magnetic materials.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for granulating a magnesium oxide raw material for molding, and in particular to a method for granulating a magnesium oxide raw material for molding, which is suitable for producing electronic materials and sheaths for firing magnetic materials. Regarding a granulation method.

[Prior Art] Conventionally, a press molding method has been mainly used for molding magnesium oxide shoes and the like used for firing electronic materials and magnetic materials. The raw material used in this press molding method is granulated fine powder of magnesium oxide.
The granulation method is classified into mixed granulation, forced granulation, heat utilization type, etc., and many methods for each are known.

By the way, in the press molding method, the fluidity of the raw material is an extremely important factor that determines the quality of the product obtained.

Conventionally, in order to obtain granulated powder with high fluidity, a spray drying granulation method has been exclusively employed.

[Problems to be solved by the invention] However, since magnesium oxide is hydratable, in the spray drying granulation method, a large amount of non-aqueous organic solvent must be used as a suspending solvent for slurry preparation. .

For this reason, the cost required for granulation becomes large, leading to a rise in manufacturing costs. Furthermore, the use of non-aqueous organic solvents should be avoided as much as possible since they may have an adverse effect on workers and cause environmental pollution problems.

[Means for Solving the Problems] The method for granulating a magnesium oxide raw material for molding of the present invention involves first granulating magnesium oxide powder by a stirring and mixing method using a binder solution containing a surfactant, and then It is characterized by uniform particle size using a crushing method.

The present invention will be explained in detail below.

In the present invention, first, a magnesium oxide raw material is pulverized to obtain a fine powder preferably having an average particle size of about 1 to 2 μm.

This is put into a mixer such as a Henschel mixer together with a binder solution containing a surfactant, and the fine magnesium oxide powder is mixed with the binder solution and granulated with stirring. The binder solution used here is 3.0 to 40% by weight, especially 20% by weight.
1 to 6% by weight for a solution containing binder.
Preferably, 0% by weight surfactant is added. Note that polyvinyl butyral or the like is generally used as the binder, and ethyl alcohol or the like is used as the solvent. Stearic acid or the like is used as the surfactant.

Further, the amount of the binder solution used is preferably 5 to 15% by weight relative to the magnesium oxide fine powder.

In addition, in the present invention, as the mixer, in addition to the Henschel mixer, a kneader, Eirich mixer, etc. can also be used.

Next, the stirred granules obtained by stirring and granulating are crushed by a crushing tool such as a hammer using a crushing granulator, and passed through a screen to reduce the particle size.

Arrange.

As the crushing and granulating machine, a crushing and granulating machine such as a rotating knife (vertical) type, a rotating knife (horizontal) type, and a rotating bar type can be used.

According to such a method of the present invention, a magnesium oxide granulated powder having extremely excellent fluidity and having a particle size distribution in the range of 60 to SOO μm can be obtained.

[Function] In the present invention, raw material powder is granulated by a composite granulation method that involves a two-step granulation process of stirring and mixing and crushing.

In the composite granulation method of the present invention, the binder solution is appropriately dispersed and mixed when the raw material magnesium oxide powder is rotated and fluidized by the rotation of the rotary blade of the mixer during stirring and mixing.

Therefore, there is no need to prepare a slurry, and granulation can be performed using only the solvent of the binder solution, so only a small amount of solvent can be used, and the impact on the human body and environment is extremely small.

In addition, in the crushing method, the powder crushed by the crusher passes through a screen to produce small and uniform particles.
High-quality magnesium oxide powder is obtained.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 1000 g of fused magnesium oxide with an average particle size of 1.6 μm
and 5.0 g of surfactant (“Polynon 〇-44” manufactured by Tetsuno Kasei (main ingredient: polyethylene glycolmon))
20% by weight binder solution ("Serna 5E-
604J Nakaya Yushi Co., Ltd. (main ingredients: waxes, solvent: ethyl alcohol) 75g and 200g in a Henschel mixer.
The mixture was mixed and granulated with stirring at ~600 rpm for 3 minutes. Next, the obtained granules were impact-pulverized using a hammer rotating at 90 rpm in a crushing granulator.

The granulated powder thus obtained had high fluidity, a compacted apparent specific gravity of 2.00, and a degree of compression of 6.3%. Further, when this granulated powder was molded at a press pressure of 1000 kg/crn'', the density of the molded product was extremely high at 2.72 g/err?.

Example 2 Granulation was carried out in the same manner as in Example 1, except that the surfactant and binder solution were replaced with those shown below.

Surfactant: Type: Polyethylene glycol (average molecular weight 400) (Wako Pure Chemical Industries) Amount used: 5.0g Binder solution: Binder: Polyvinyl butyral (rG-7,211J Dai-Kogyo Seiyaku) Solvent: Ethyl alcohol concentration : 18.8% by weight Amount used: 80g The obtained granulated powder has high fluidity and has an apparent specific gravity of 1.
93, and the degree of compression was 10.1%. In addition, when this granulated powder was molded with a press pressure of 1000 kg/cm',
The density of the molded product was extremely high at 2.51 g/Cm'.

Comparative Example 1 1000g of the electrofused magnesia raw material used in Example 1 was mixed into 2.
A slurry was prepared by suspending OIL in a solvent (ethyl alcohol), and the slurry was spray-dried using a spray dryer to form granules.

The fluidity of the obtained granulated powder was considerably inferior to that obtained in Example 1.2, and the compacted apparent specific gravity was 1°58, the degree of compaction was 17.4%, and the powder was 1000 kg/c. rn'
When molded with a press pressure of , the density of the molded product was 2.40.
g/CJT! 'Met.

[Effects of the Invention] As detailed above, the method of granulating the magnesium oxide raw material for molding of the present invention is a composite granulation method of a stirring and mixing method and a crushing method, and the amount of solvent used is significantly reduced. Therefore, magnesium oxide granulated powder can be obtained efficiently and at low cost in a safe working environment. Moreover, since the obtained granulated powder has an extremely uniform particle size distribution, its fluidity is extremely high, and it can be used to mold magnesium oxide compacts that require high properties such as electronic materials and sheaths for firing magnetic materials. It is extremely useful as a raw material powder.

Claims (1)

[Claims] (1) A method for granulating a magnesium oxide raw material for molding, which comprises first granulating magnesium oxide powder by a stirring and mixing method using a binder solution containing a surfactant, and then adjusting the particle size by a crushing method.