Source Lei little knowledge, nano calcium carbonate commonly used 10 categories of surface modifiers.
With the gradual expansion of the application field of nano-calcium carbonate, in order to give full play to the advantages of nano-calcium carbonate and improve the performance of nano-calcium carbonate, different surface modification methods and modifiers must be used for surface modification. Let's take a look at the 10 types of surface modifiers commonly used in nano calcium carbonate.
1. Titanate coupling agent
Titanate coupling agent can be divided into single alkoxy type, coordination type and chelating type, in order to improve the uniformity of the reaction, the need to use inert solvent for dissolution and dilution, and then in the form of spray surface modification machine, can be better with calcium carbonate particles for dispersion and mixing, surface chemical coating.
2. Aluminate coupling agent
The alkoxy at one end of the aluminate can react with the free protons on the surface of calcium carbonate, and the other end can be wound or cross-linked with the polymer molecular chain, and its performance is better than that of titanate.
3. Borate ester coupling agent
The use of borate ester coupling agent as a modifier has many advantages: non-toxic and antibacterial, excellent coupling function, good thermal stability, and good hydrolysis resistance. Therefore, boric acid ester as a nano calcium carbonate modifier, not only for dry surface modification process, but also can be used for wet modification treatment.
4. Fatty acid (salt)
The action mechanism of fatty acid (salt) is to use a large number of hydrophilic hydroxyl groups distributed on the surface of calcium carbonate, showing the characteristics of strong alkaline, and its RCOO-reacts with Ca2, CaHCO3, CaOH and other components in calcium carbonate slurry to generate fatty acid calcium precipitate, which is coated on the surface of calcium carbonate particles.
5. Phosphate and condensed phosphoric acid
Phosphate ester (salt) modifier also belongs to the anionic surfactant, mainly through the phosphate ester corrosion calcium carbonate surface to generate phosphate ester calcium and phosphate hydrogen calcium, which tightly coated on the surface of nano calcium carbonate particles, long chain alkyl outward arrangement, making nano calcium carbonate hydrophobic.
6. Quaternary Ammonium Salts
Quaternary ammonium salt is a kind of cationic surfactant, one end of its molecule can be crosslinked with polymer materials, and the other end can be charged with positive electrostatic adsorption on the surface of calcium carbonate.
7. Reactive monomers and active macromolecules
In the reactive monomer, small molecule carboxylic acid with unsaturated bond can interact with nano calcium carbonate to disperse nano calcium carbonate; using its reactivity (unsaturated bond), it can be grafted with polyolefin to form a graft and strengthen the interface between nano calcium carbonate and polymer.
The polymer can be adsorbed on the surface of calcium carbonate, so that calcium carbonate has charge characteristics and forms a physical or chemical adsorption layer on the surface of calcium carbonate particles, increases the distance between particles, prevents the adhesion and agglomeration of calcium carbonate particles, and improves the dispersion. Commonly used polymers are mainly oligomers, polymers and water-soluble polymers.
9. Super Dispersant
Hyperdispersants are different from traditional surfactants and are mainly composed of a solvent segment and an anchoring segment. The anchoring segment is generally a polar group, which can be tightly combined with the particle surface in the form of single-point anchoring or multi-point anchoring; the solvent segment has different polarities and is suitable for polymer modification with different polarities.
Inorganic modifiers generally can not make calcium carbonate from hydrophilic to hydrophobic, but can improve the dispersion and acid resistance of nano calcium carbonate, if combined with other modifiers, the effect is better. Commonly used mainly metaphosphoric acid (salt), polyphosphoric acid (salt), aluminate (salt), alum, barium salt, etc.
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Barium sulfate is based on barite as the main raw material, through beneficiation, ore washing, crushing and other processes. Barium sulfate has a hardness of 3~3.5 (Mohs) and a specific gravity of 4.3~4.7. It has the characteristics of high specific gravity, low hardness and brittleness. Barite is almost insoluble in water, ethanol and acid, soluble in hot concentrated sulfuric acid. With the development of some high-performance barium sulfate products, the application field of barium sulfate is constantly expanding.