What is the difference between light, heavy and nano calcium carbonate, modified?

Calcium carbonate is an important and useful chemical raw material, which is used as a reinforcing agent and filler in rubber, paper, ink, coating, plastic, food, cosmetics and other industries. According to the different production methods of calcium carbonate, it can be divided into light calcium carbonate and heavy calcium carbonate and nano calcium carbonate.

Light calcium carbonate, also known as precipitated calcium carbonate, is prepared by chemical processing methods; heavy calcium carbonate, also known as ground calcium carbonate, is prepared by mechanically crushing natural limestone, calcite, chalk and so on.

There are certain differences in the particle size and surface characteristics of heavy calcium carbonate and light calcium carbonate, so there will also be differences in the effect of use.

Nano calcium carbonate refers to calcium carbonate products with a particle size of 1 to 100 nm, including ultra-fine and ultra-fine calcium carbonate products.

Summary of Modification Methods - Modification methods for heavy calcium carbonate

Physical coating modification

Physical coating modification is to mix the modifier with heavy calcium carbonate in a certain proportion, under the action of dispersion force, the modifier is adsorbed on the surface of heavy calcium carbonate by physical forces such as van der Waals force or electrostatic gravity, forming a single, double or multi-layer coating layer.

Chemical modification of the surface

Surface chemical modification refers to the use of functional groups in the modifier molecule and the active point of the surface of the heavy calcium carbonate powder for chemical reaction or chemical adsorption by a certain method, so that the modifier is coated on the surface of the heavy calcium carbonate particles, enhancing the compatibility and dispersion of the heavy calcium carbonate and the filled organic matrix, thereby improving the processing performance and physical and mechanical properties of the composite material.

Mechanical chemical modification

Mechanical chemical modification is the use of mechanical means such as crushing and friction to make the lattice of the heavy calcium carbonate powder shift and change the crystal form, while the system temperature increases and the internal energy increases.

In the industrial production of heavy calcium carbonate, grinding and crushing and surface modification are generally carried out separately, if in the process of heavy calcium carbonate crushing at the same time add modifier to modify its surface, not only can use the physical mechanical force of crushing to enhance the surface modification effect, but also to prevent the agglomeration phenomenon caused by heavy calcium carbonate particles too fine.

Surface deposition modification

Surface deposition modification is the use of suitable methods to precipitate the modifier on the surface of heavy calcium carbonate, which is one of the commonly used methods for surface modification of inorganic mineral pigments.

Suitable for industrial production, the process flow is simple, by controlling the reaction conditions, the right particle size and purity can be obtained.

Lightweight calcium carbonate modification method

Fatty acid (salt) modification

Stearic acid (salt) is a commonly used surface modifier of calcium carbonate. The modification process can be either dry or wet. General wet processes use stearates, such as sodium stearate.

In addition to stearic acid (salt), other fatty acids (esters), such as phosphates and sulfonates, can also be used for surface modification of calcium carbonate. Studies have shown that after surface modification of calcium carbonate with a special structure of polyphosphate (ADDP), the surface of calcium carbonate particles is hydrophobic and lipophilic, and the average agglomeration particle size in the oil is reduced.

The active calcium carbonate modified with fatty acids (salts) is mainly used to fill PVC plastics, cable materials, adhesives, inks, coatings, etc.

Coupling agent modification

Coupling agent is a sexual structure compound, through the reaction group and calcium carbonate surface hydroxyl group for chemical bonding, the polar group of its molecules, can react with the functional group on the surface of calcium carbonate particles, the formation of a stable chemical bond. The other end can be chemically reacted or physically wound with organic polymers, thereby tightly combining two materials with large polarity differences, and has good compatibility, and gives the composite material better physical and mechanical properties.

According to its structure, it can be divided into silanes, titanates, aluminates, titanium aluminates, zirconate aluminates and complexes.

Polymer modification

Surface modification of calcium carbonate using polymers can improve the stability of calcium carbonate in organic or inorganic phases (systems). These polymers include oligomers, polymers and water-soluble polymers such as polymethyl methacrylate (PMMA), polyethylene glycol, polyvinyl alcohol, polymaleic acid, polyacrylic acid, alkoxystyrene - styrene sulfonic acid copolymers, polypropylene, polyethylene and the like.

Plasma and radiation modification

The results of low-temperature plasma modification of heavy calcium carbonate (1250 mesh) powder using inductively coupled glow discharge plasma system and using argon (Ar) and high-purity propylene (C3H6) gas mixture as plasma bodies showed that the calcium carbonate filler treated with Ar-C3H6 gas mixture had good interfacial adhesion to polypropylene (PP).

Nano calcium carbonate modification method

1. Modification of local chemical reactions

Local chemical reaction modification is a method of first adding treatment agents (coupling agents, organic substances, inorganic substances, etc.), and then the nano calcium carbonate surface functional group chemically reacts with it to achieve the purpose of modification. At present, the surface modification of nano calcium carbonate is applied in this method.

There are two main types of local chemical reaction modification processes: dry and wet. The dry method is to add nano calcium carbonate powder and surface modifier to the modifier in turn to carry out surface modification. Suitable for surface modification with coupling agents.

2. Surface coating modification

A modified method of connecting the nano-calcium carbonate particles and the coating by van der Waals force or physical methods. The surface modifier or superdiscent agent is added to the preparation solution of nano calcium carbonate, while producing nano calcium carbonate, the surface modifier is coated on the surface of calcium carbonate, so that the final product exists in the form of uniform particles.

3. Masterbatch filler modification

Masterbatch filler is a new type of filler, by mixing a certain proportion of resin masterbatch, calcium carbonate and surfactant, the masterbatch filler is prepared while the surface modification of calcium carbonate. According to the different matrix resins used, the common masterbatch fillers mainly include polyethylene wax calcium carbonate masterbatch, irregular polypropylene calcium carbonate masterbatch (APP masterbatch) and resin calcium carbonate masterbatch filler.

4. High performance surface modification

A method of modification using plasma or high-energy rays such as X-rays, γ rays, etc. The surface modification of the plasma to the CaCO3 powder is mainly based on the use of plasma polymerization technology, first of all, the monomer is activated to produce gaseous free radicals, and then adsorbed on the solid surface to become a surface radical, and then polymerization reaction occurs with the plasma or gas phase primitive monomer, forming a polymer film on the surface of calcium carbonate to achieve modification.

epilogue

In short, surface modification is an important means necessary to improve the application performance of calcium carbonate, improve applicability, expand market and dosage. Surface modified calcium carbonate, from the traditional filler to a multifunctional modifier, should be a wider range and more popular.

In the future, functionalization and specialization will become the main trend of calcium carbonate development, and the product structure will also undergo great changes. Products such as nano-scale calcium carbonate, ultra-fine calcium carbonate, medical grade and food grade calcium carbonate; a variety of surface modification of special calcium carbonate, such as natural rubber, synthetic rubber, coatings for lightweight calcium carbonate, these high value-added calcium carbonate products market demand will be larger and larger, and product quality will also be the key to the survival and development of enterprises!