How to control the oil absorption value of magnesium hydroxide
As an inorganic filler, magnesium hydroxide has been widely used in many industries such as rubber, plastics, coatings, inks, pharmaceuticals and food. Among the indicators related to the quality of magnesium hydroxide products, the oil absorption value has a very important influence on the application of the product.
The oil absorption value, also known as resin adsorption, is an index of the amount of resin absorbed by the filler. In addition to the chemical composition and purity of the powder material, the oil absorption value is also related to the chemical properties of its surface, and the particle size, specific surface area and adsorption properties of the powder are different. The oil absorption value can change the compatibility of magnesium hydroxide with the action of polymers, and has a certain influence on the quality, performance and use of the material.
In simple terms, a high oil absorption value "wastes" a large amount of resin and the effect of filling magnesium hydroxide to reduce production costs is diminished. In addition, if the formulation contains liquid additives, magnesium hydroxide with a low oil absorption value should be used, while inorganic powders with a high oil absorption value will require more coupling agents.
The way to reduce the oil absorption value of magnesium hydroxide.
1)Control the particle shape.
The oil absorption value of magnesium hydroxide and the production process has a great relationship. In the case of particle shape without special requirements, can use crystal control agent, control crystal shape and specific surface area, so as to reduce its oil absorption value.
2)Control fineness and particle size distribution.
Ordinary field of magnesium hydroxide product application, the fineness and particle size distribution requirements are not high, can be appropriate to choose the particle size distribution gap between the compound products, so that small particles will enter the large particle space, the stacking density becomes larger, the overall oil absorption of the product will be reduced.
For high quality product applications, high fineness, narrow particle size distribution of magnesium hydroxide can help improve the performance of the product, this time it is necessary to solve the problem of oil absorption value through surface modification.
3)Surface modification.
Surface modification is one of the important means to effectively reduce the oil absorption value of the powder. After the surface modification of magnesium hydroxide, aggregated state particles reduce, dispersion improve, reduce the gap between the particles, in addition, modified molecules make the surface polarity of magnesium hydroxide weakened, the friction between the particles reduce, lubricity improve, the powder accumulation more closely, the accumulation density increases, oil absorption value naturally reduced.
Magnesium hydroxide production process variables on the impact of oil absorption value.
1)The influence of secondary carbonisation time.
2)The influence of the amount of crystal control agent.
Carbonisation reaction includes the generation of magnesium hydroxide nuclei and crystal growth, at the beginning of the carbonisation reaction, with the increase in the amount of crystalline control agent, the nucleation rate is greater than the growth rate, the produced nano magnesium hydroxide particle size is small, the specific surface area is large, high yield value, but the oil absorption value is also increased accordingly.
3)The influence of surfactant dosage.
With the increase in the amount of surface treatment agent, magnesium hydroxide oil absorption value decreases. But when the amount of treatment agent increased to a certain extent, the oil absorption value almost no longer down, and the system in excess of treatment agent leads to yield value reduction.
