JPH0146464B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to glass beads that have high mechanical strength and excellent wear resistance, and in particular, glass beads that have high hardness and excellent chemical durability as glass beads for filling in crushing and dispersion mills. Concerning sexual glass beads. [Technical background of the invention and its problems] Conventionally, sand mills and the like using glass beads have been used to micronize powders such as pigments, paints, and magnetic materials for magnetic tapes, and to homogenize them by mixing them with solvents. dispersant is used. This sand mill uses stirring blades that rotate at high speed to stir the raw material powder, glass beads, and dispersion material housed in a container at high speed, and when these collide and rub against each other, the raw material powder is It is intended to be homogeneously dispersed. These glass beads are generally made by crushing pieces of soda lime-based ordinary plate glass to a predetermined particle size, heating them, and forming them into a spherical shape. This type of glass beads has low chemical durability, and alkaline components elute, which changes the PH value of the raw material during dispersion and adversely affects the chemical and physical properties of the product.
In addition, the mechanical strength, especially the hardness, is low, so the wear rate is fast, and in order to maintain the desired dispersion efficiency, the glass beads must be replaced frequently. It has the disadvantage of contaminating the body and significantly reducing the quality of products. Also, beads made of zircon or corundum, which have high hardness, are known as dispersing materials other than glass, but these beads have the drawback of damaging the dispersing material container and stirring blades due to their extremely high hardness. Therefore, the conditions for glass beads suitable for sand mills are that the particle size of the glass beads should be constant in order to maintain the dispersion effect and that they would not be easily worn out, and that they should have high mechanical strength and be resistant to impacts such as collisions and not shatter.
Glass beads that satisfy all of these properties are not commercially available, such as being difficult to elute when used as a dispersion solvent and having excellent chemical durability. [Object of the Invention] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide wear-resistant glass beads that exhibit superior properties in all of the above conditions compared to soda lime glass beads. shall be. [Summary of the Invention] In order to achieve the above object, the present invention strengthens alkali-free glass containing a large amount of ZnO and B ₂ O ₃ to increase its hardness, have excellent wear resistance, and The present invention provides glass beads that also have excellent chemical durability. That is, the present invention uses SiO ₂ 28-65% by weight percentage,
ZnO 10~45%, _B2O3 5~25%, _{Al2O3 1} ~ ₁₅ %,
Molten glass consisting of 3 to 15% of CaO + MgO + BaO + SrO + TiO ₂ is poured onto a rotating disk and dispersed to form glass beads with a diameter of 0.7 to 4 mm into a spherical shape, which is then heated to a temperature above the strain point of the glass to form a molten alkali nitrate or alkali molten salt. These are glass beads that have been strengthened by placing them in oil or water and rapidly cooling them. The reason why the glass composition of the present invention is limited to the above range is as follows. SiO ₂ is one of the basic components necessary for glass formation, but if it is less than 28% by weight (the same applies hereinafter), the mechanical strength and chemical durability will decrease, and the coefficient of thermal expansion will also increase, so the heat resistance Impact resistance decreases, causing cracking during bead molding, and if it exceeds 65%, meltability decreases and viscosity at high temperatures increases, making it difficult to mold beads. ZnO increases the hardness of the glass, lowers its viscosity at high temperatures, and makes it easier to strengthen, but if it is less than 10%, the hardness of the glass does not increase, the abrasion resistance is poor, and it is difficult to strengthen. If it exceeds %, the glass becomes brittle, its mechanical strength deteriorates, and there is a risk that the glass beads will be damaged when used in a sand mill. B ₂ O ₃ is a basic component of glass formation together with SiO ₂ ,
It improves meltability and chemical durability, but if it is less than 5%, no effect can be expected, and if it exceeds 25%, abrasion resistance and chemical durability are significantly reduced. Al ₂ O ₃ improves the chemical durability of glass, but
If it is less than 1%, no effect can be expected, and if it exceeds 15%, the meltability will be significantly reduced. CaO, MgO, BaO, SrO and _TiO2 are effective in improving wear resistance and chemical durability, but 2
If it is less than 10%, the effect cannot be expected and the glass beads have low hardness and become brittle, and if it exceeds 10%, phase separation tends to occur and the meltability deteriorates. Alkali metal oxides such as Na ₂ O, K ₂ O, Li ₂ O, etc. are not added in order to avoid elution of alkaline components during dispersion, and even if they are contained, they are contained in trace amounts of less than 1% from raw material impurities. It does not affect chemical durability. Next, the diameter of the glass beads of the present invention is 0.7 to 4 mm.
The reason why the glass beads are limited to this range is that when the glass beads are used as a dispersion promoter in a sand mill or the like, if the diameter of the beads is smaller than 0.7 mm, the beads are lightweight, so kinetic energy is insufficient during milling, and the crushing effect is poor. Furthermore, if the diameter exceeds 4.0 mm, the gaps between the beads will be large and the number of collisions will be small, resulting in a decrease in the dispersion effect. Next, when molten glass having the above composition is made to flow down continuously onto the top surface of a disk rotating at high speed with a viscosity of 100 voices or less, shock waves are transmitted to the glass flow upon contact with the disk, and the glass flow is dispersed. However, it is scattered by centrifugal force, and while flying through the air, it is shaped into a spherical shape by surface tension and becomes glass beads. The particle size of glass beads can be adjusted arbitrarily by changing the rotation speed of the disk, but since they are manufactured with a particle size distribution within a certain range, it is difficult to obtain glass beads with a desired particle size. Sorted by sieving. The glass beads thus obtained are treated by the usual liquid cooling strengthening treatment method described above to obtain wear-resistant glass beads. [Embodiments of the Invention] Next, embodiments of the present invention will be described and explained. No. 1 to No. 5 in the table indicate examples according to the present invention,
No. 6 is a comparative example using conventional glass beads.
In addition, the characteristic value wear resistance is 2 kg for the sand mill of 2.
Add the glass beads and water and stir with the stirring blade 3000 times/
This is the value expressed as a percentage of the abrasion loss of the glass beads after 48 hours of rotation in minutes. Compressive strength is a compressive crushing strength measurement value using an autograph compression testing device. Hardness is measured using a Bitkers hardness tester.
It is shown as the value obtained when the weight is 100g. Water Resistance A glass elution test was performed by immersing 5 g of glass beads with a diameter of 1.5 ± 0.1 mm in 200 ml of warm water (96 to 99°C) for 4 hours, and the eluate was measured using an atomic absorption spectrophotometer.
Concentration values (ppm) of Li, Na, K, Ca, Mg, and Ba are shown.

【table】

〔Effect of the invention〕

As described above, the glass beads of the present invention are superior to conventional glass beads in terms of abrasion resistance, mechanical strength, chemical durability, etc. Therefore, when used as a powder dispersion promoter, the following effects can be achieved. play. Due to its high hardness and excellent abrasion resistance, the glass beads have a long lifespan and can be used continuously for a long period of time. Since the mechanical strength is high and the glass beads themselves are less likely to be crushed, it is possible to prevent glass bead fragments from being mixed into the powder and improve the quality of the product. Since it has excellent chemical durability, the amount of alkali elution is small, causing no chemical or physical changes in the dispersing material, and it can be stably used in acidic or alkaline dispersing materials. Note that the glass beads of the present invention are not limited to the above uses.

Claims (1)

[Claims] 1 SiO ₂ 28-65%, ZnO 10-45% by weight percentage,
_{B2O3 5-25} %, _{Al2O3 1-15} %, CaO+MgO+
A wear-resistant glass bead characterized by reinforced glass beads having a diameter of 0.7 to 4 mm formed into a spherical shape by flowing down and dispersing molten glass consisting of 3 to 15% of BaO + SrO + TiO ₂ onto a rotating disk.