The so -called composite calcium carbonate products usually refer to the use of heavy calcium carbonate as the main body (> 50%) and a certain percentage of light -quality calcium carbonate powder. Through the complex and modified technology Sexuality can be well balanced, heavy and calcium differences, and the advantages of both two. While greatly reducing product costs, they expand the application scope of the product and improve the quality of the product.
Complex activated calcium carbonate surface modification method
The correct choice of modifiers must not only consider the affinity mixed solubility of the modifier and calcium carbonate and its use of pigment powder, but also consider the mixed solubility of other chemicals of the modified agent and the matrix, especially for it for for it for, especially for it for, especially for it for, especially for it for, especially for it. The compatibility effect of the modified calcium and auxiliary materials of the plastic system.
At present, the surface modification methods of calcium carbonate mainly include the modification of the surfactant, the modification of the coupling agent, the reactive monomer and the activated macromolecular modification, and the legal modification of the original position.
(1) Surface active agent modification method
At present, there are many types of surfactants for modified calcium carbonate, large production capacity, and low prices. They can be divided into two categories: fatty acids (salt) and titanate.
(2) Puppet coupling modification method
One end of the coupling molecules is a polar group, which can chemically react with the hydroxyl groups on the surface of calcium carbonate to form a stable chemical bond; the non -polar group on the other end is covered on the surface of the calcium carbonate particles to make the surface kiss on the surface Oilization can reduce the surface freedom of the particles, improve mixing with resin, and give better physical mechanical properties with better composite materials. At present, the coupling agent used in calcium carbonate is mainly titanate coupling agents and aluminate coupling agents.
(3) Polymerization method
The polymer can be adsorbed on the surface of calcium carbonate, so that calcium carbonate has a charge characteristics, and forms a physical and chemical adsorption layer on its surface, preventing the agglomeration of calcium carbonate particles and improving decentralization. It is generally believed that calcium carbonate of polymer envelope can be divided into two categories:
One type is to adsize the polymer to the surface of calcium carbonate, and then trigger its aggregation, so as to form a very thin polymerization film layer on its surface;
The other is to dissolve the polymer to add calcium carbonate in an appropriate solvent. When the polymer is gradually adsorbed on the surface of calcium carbonate, the solvent is eliminated to form a envelope.
(4) Original aggregation modification method
In the original polymerization, the particles were first dispersed evenly in the monomer, and then the polymerization was caused by the cause of the cause. Compared with the traditional filling polymer material, the polymerization of the original position ensures the uniform dispersing of the filling particles.
Analysis of common problems and reasons in the application
The problems that often occur in plastic in plastic are mainly reflected in the effective dispersing of the powder, the surface gloss of the product, the extrusion performance in the process of product processing, and the stability of the color.
(1) Disted problems of powder
★ When the surface covering of the active agent is incomplete and the oil absorption value is high, it is easy to cause the compatibility of the material sticky wall and the DOP such as DOP when the dried powder mixing
★ The pH value of the product is high, especially when it is above 10 or more, the dielectric performance of the surface of the powder particles changes, the amount of charge and electricity increases, and the product obviously appears.
★ Heavy calcium can effectively improve the liquidity of processing, but if the heavy calcium is added with too much and the granularity is large, it is easy to cause poor surface flatness and rough feel.
(2) Product surface gloss problem
★ When the particle size of the powder is large, the surface of the squeezing particles is obviously small particles after plasticizing the surface of the squeezing particles, the surface reflects decreases, and the light scattering effect makes the surface of the glue the surface darker darker;
★ Due to the plasticization of the rubber, the latex -shaped air bubbles are formed. After the glue is squeezed out and cooled, the position of the tiny bubbles forms the acupuncture point, the surface becomes uneven, and the gloss is reduced;
★ When the material is better after the material is squeezed out, but when the rubber is stored for a period of time, the surface appears “fog surface”. The main reason is that because the hard fat acid in the rubber is excessive, some hard fat acids are analyzed;
★ The difference in the surface flatness of the product is mainly the gel viscosity and poor liquidity.
(3) Squeezing performance is poor
★ Slow -extruded speed is due to excessive filling of calcium carbonate powder, which causes increased viscosity, difficult to plasticize, and reduces the extrusion speed;
★ The poor liquidity of the rubber is mainly due to the strong adsorption capacity of light calcium powder particles to the plasticizer, which affects the normal plasticization of the rubber, which extend the time of plasticization.
(4) Color stability problem
★ Calcium carbonate powder itself is low and unstable;
★ Powder contains a small amount of oxide impurities;
★ The pH value of calcium carbonate powder is high;
★ The oil absorption value of calcium carbonate powder is high.
Key points for re -activated calcium calcium carbonate production
In order to produce high -quality rehearsal active calcium carbonate to meet the needs of downstream users, you need to pay attention to the following points:
(1) Choose high -quality raw materials
Fangli stone and limestone should be raw materials of high -white, low impurities to control magnesium oxide content in the ore, and the optimization of magnesium oxide is less than 0.5%. Magnetic magnesium oxide content can reduce the pH value and oil absorption value of the powder.
(2) Optimize the proportion of calcium and light calcium proportion and particle size range
While effectively improving the liquidity of rubber, it can also effectively improve the surface quality of the product.
(3) Strictly control the equipment used in powder processing
Generally, stainless steel should be selected to avoid mixing of impurities such as rust. Especially the activation equipment and drying equipment must be made of stainless steel to avoid rust due to the contact with the active agent (generally slightly acidic); the wet material in the contact of the drying equipment can easily rust the carbon steel equipment.
(4) Calcium carbonate powder surface covering process
When the surface is covered (insufficient amount of the covering agent), the performance of the powder of the powder is reduced, and the compatibility of the plasticizer is reduced. After the calcium carbonate carbonate is covered by the surface activated agent, the high activation is obtained.