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Yuan Lei's Little Knowledge | Three Modification Methods of Ultrafine barite Powder

Release time:

2024-01-29 09:34

In the modification of barite powder, the choice of modifier will directly affect the modification effect of barite, as well as the application effect of filler in polymer materials, so the choice of modifier plays a key role in the preparation of active barite. In the modification of inorganic powder, modifiers can be divided into surfactants, coupling agents, organic polymers, unsaturated organic acids, metal oxides and their salts, and hyperdispersants. At present, in the preparation of active barite, the commonly used modifiers are surfactants, coupling agents, metal oxides and their salts.

 

 

1. surfactant modification

Surfactants can be classified into anionic surfactants, cationic surfactants and nonionic surfactants according to the chargeability of their active groups. The surface electrical properties of barite powder are determined by the charged ions on the surface of the powder. Under different pH values, barite powder will have different charges. When the pH is less than the isoelectric point, the surface of barite powder is positively charged. When the pH is greater than its isoelectric point, the surface is negatively charged.

The surface of the modified barite powder increases the steric hindrance between the particles due to the connection of the oleophilic base, prevents the particles from approaching each other, avoids the particles from colliding and settling, and improves the dispersion in the polymer material.

1. Anionic surfactant modification

The part that plays a surface active role after ionization in water is a negatively charged surfactant called an anionic surfactant. Stearic acid is a widely used anionic surfactant, one end of the molecule is a long chain alkyl R, the structure is similar to the polymer structure, so it has good compatibility with the polymer base material; the other end of the molecule is-COOH, which can be physically and chemically adsorbed with inorganic mineral powder.

The application of unmodified barite mineral powder in rubber is limited due to its poor affinity with rubber interface. Filling the modified barite mineral powder into rubber can not only improve the added value of barite, reduce the production cost of rubber materials, but also provide technical reference for the preparation of new rubber materials with wear resistance, aging resistance and special hardness.

As a paint filler, the modified barite mineral powder must have good affinity with organic paint and be evenly dispersed in the matrix; at the same time, it can increase the gloss and adhesion of the paint, and has good acid and alkali resistance.

2. Cationic surfactant modification

When the surface of the barite powder is negatively charged, it is necessary to use a cationic surface modifier, such as methyl oleic acid ammonium chloride, dioctadecyl dimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride, etc. The positively charged active groups react with the negative charge on the surface of the barite, so that the surface of the mineral powder is connected with a long-chain alkyl group, which increases the steric hindrance between the particles and avoids the agglomeration of the particles during the collision, so that the barite powder is better dispersed. At the same time, the long-chain alkyl group is similar to the structure of the polymer material, and the two have good affinity.

3. Non-ionic surfactant modification

The hydrophilic group and the lipophilic group in the non-ionic surfactant can interact with the filler and the polymer material respectively, and strengthen the connection between the two, so as to improve the dispersion and affinity of the system. In the preparation of active barite, the effect obtained by using a nonionic surfactant alone is not good.

 

 

2. coupling agent modified barite

1. Modification of silane coupling agent

Silane coupling agent is a kind of organic silicon compound which contains two different chemical properties at the same time. It can build a "bridge" between organic polymer materials and inorganic materials, so that two kinds of materials with large differences in properties can produce a good interface and be firmly combined together.

The superfine powder of barite modified by silane coupling agent is used as the filler of polymer materials, which has good compatibility and affinity with polymer materials and is evenly distributed in the matrix.

2. Modification of titanate

Titanate coupling agent is a new type of coupling agent developed by Kenrich Petrochemical Company in the mid-1970s. It has good modification effect on many inorganic particles. According to its chemical structure, it can be divided into single alkoxy type, chelating type and coordination type. After modification, the oil absorption of barite ore powder decreased by 15%. When the modified barite ore powder is added to the powder coating, the powder coating has smooth appearance and high gloss, which can improve the leveling, gloss and mechanical properties of the powder coating.

Modification of 3. metal oxides and their salts

The surface potential of barite is not only related to the surface adsorption, but also related to the adsorption of metal ions when there is characteristic adsorption. In the presence of characteristic adsorbed metal cations, the positive surface charge increases; in the presence of characteristic adsorbed anions, the surface charge becomes more negative.

The surface of barite powder can be made into composite conductive powder by chemical co-precipitation and corresponding physical and chemical treatment.

Method, barite, modification, surfactant, surface, coupling agent, polymer material, particle, good, adsorption

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