JPH0444623B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to glass beads with high mechanical strength and excellent abrasion resistance, and in particular, borosilicate glass beads with high hardness and excellent scientific durability as glass beads for crushing and dispersion mill filling. This invention relates to wear-resistant glass beads made of alkaline earth alumina glass. [Technical background of the invention and its problems] Conventionally, sand mills and the like using glass beads have been used to make pigments, paints, magnetic materials for magnetic tapes, etc. into fine particles, or to mix and homogenize solvents. dispersant is used. This sand mill stirs the raw material powder, glass beads, and dispersion material housed in a container using stirring blades that rotate at high speed, creating a high-speed flow.The raw material powder, glass beads, and dispersion material housed in a container are stirred into a high-speed flow by colliding and rubbing against each other. It disperses homogeneously. 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 weak chemical durability, and alkaline components may be eluted, causing the pH of the raw material to deteriorate during dispersion.
Changes in values and adversely affect the scientific and physical properties of the product. In addition, the mechanical strength, especially the hardness, is low, so the wear rate is high, 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. In addition, beads made of zircon or corundum, which have high hardness, are known as dispersing materials other than glass, but they have the drawback of damaging the dispersing material container and stirring blades due to the extremely high altitude. 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 dissolve in dispersion solvents and having excellent chemical durability. Furthermore, there is a demand for glass beads with a composition that does not contain arsenous acid or lead, which can elute or turn into fine powder and have a harmful effect on the human body. [Object of the Invention] The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide abrasion-resistant alkali-free glass beads that exhibit superior properties in all of the above conditions compared to soda lime glass beads. With the goal. [Summary of the Invention] In order to achieve the above object, the present invention uses glass that does not contain alkali components and contains large amounts of BaO, CaO, and B ₂ O ₃ to achieve high hardness, wear resistance, and chemical resistance. It is made of molded glass beads with excellent durability. i.e. SiO ₂ 25-50 in weight percentage
%, B ₂ O ₃ 15-28%, Al ₂ O ₃ 2-18%, CaO,
MgO, BaO, SrO alone or in combination of two or more 15~
It is a wear-resistant alkali-free glass bead with a composition of 55%. 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 25%, mechanical strength and chemical durability will decrease, and the coefficient of thermal expansion will increase, resulting in a decrease in thermal shock resistance and bead formation. Sometimes it causes cracking, and if it exceeds 50%, the meltability decreases and the viscosity at high temperatures increases, making it difficult to mold beads. B ₂ O ₃ is a basic component of glass formation together with SiO ₂ and improves meltability and chemical durability, but if it is less than 15%, the effect cannot be expected, and if it exceeds 28%, wear resistance and chemical durability are reduced. Sexuality is significantly reduced. Al ₂ O ₃ improves the chemical durability of glass, but if it is less than 2%, the effect cannot be expected, and if it exceeds 18%, the meltability will be significantly reduced. CaO, MgO, BaO, and SrO have the effect of improving wear resistance and chemical durability, but if the content of these alone or two or more is less than 15%, the effect cannot be expected and the hardness of the glass beads When it becomes low and exceeds 55%, phase separation occurs and milky whiteness occurs. Alkali metal oxides such as Na ₂ O, K ₂ O, Li ₂ O, etc. are not particularly added 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. When using the glass beads of the present invention as a dispersion promoter in a sand mill, etc., the diameter of the beads should be 0.7
It is desirable to limit the range to 4 mm. The reason for this is that if the diameter of the beads is smaller than 0.7 mm, the beads are lightweight and lack kinetic energy during milling, resulting in a poor crushing effect, while if the diameter exceeds 4 mm, the gaps between the beads become large and the number of collisions decreases, resulting in a poor dispersion effect. This is because it decreases. Next, when molten glass having the above composition is caused to flow down continuously at a viscosity of 100 poise or less onto the top surface of a disk rotating at high speed, a shock wave is 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. [Embodiments of the Invention] Next, embodiments of the present invention will be described and explained. No. 1 to No. 6 in the table indicate examples according to the present invention,
No. 7 is a comparative example using conventional glass beads.
As for the characteristics, wear resistance is 2. Put 2 kg of glass beads and water in a sand mill and set the stirring blade to 3000.
This is a value expressed as a percentage of the abrasion loss of glass beads after 48 hours of rotation at a rate of rotation per minute. Compressive strength is a compressive crushing strength measurement value using an autograph compression testing device. The hardness was expressed as a value obtained using a Bitkers hardness tester at a load of 100 g. Water resistance was determined by performing a glass elution test 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 measuring the eluate using an atomic absorption photometer. Concentration values (ppm) of K, Ca, Mg, Ba, and Sr 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., and therefore, when used as a powder dispersion promoter, the following effects can be achieved. There is. 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 does not contain alkali metal oxides, there is no contamination due to alkali elution, and no chemical or physical changes occur in the dispersion material. Since it does not contain ingredients harmful to the human body such as arsenous acid and lead, it can be safely used in the food industry.

Claims (1)

[Claims] 1 SiO ₂ 25-50%, B ₂ O ₃ 15-28% by weight percentage,
Wear-resistant glass beads having a composition of 2 to 18% Al ₂ O ₃ and 15 to 55% of CaO, MgO, BaO, SrO alone or in combination of two or more.