Molecular sieve desiccant

An aluminosilicate compound with a cubic lattice, which is mainly composed of silicon and aluminum connected by oxygen bridges to form an empty framework structure. In the structure, there are many pores with uniform pore diameter and cavities with neat arrangement and large internal surface area. In addition, it also contains metal ions with lower electricity prices and larger ion radius and water in a combined state. Because water molecules are continuously lost after heating, but the structure of the crystal skeleton remains unchanged, many cavities of the same size are formed, and the cavities are connected by many pores with the same diameter. These tiny pores are of uniform diameter and can be compared to the pores. Molecules with small diameters are adsorbed into the inside of the pores, and molecules larger than the pores are excluded. Therefore, molecules with different shapes and sizes, molecules with different polarities, molecules with different boiling points, and molecules with different saturation levels can be separated It has the function of "sieving" molecules, so it is called molecular sieve. Molecular sieves are widely used in metallurgy, chemical, electronics, petrochemical, natural gas and other industries.



Molecular sieves remove water from the crystallized synthetic zeolite (a special sodium/potassium aluminum silicate) structure, that is, "activate", and obtain a microporous powder solid with a specific pore size. Molecular sieves can selectively adsorb a mixture of small molecules, including water molecules.



The industrial molecular sieve produced by CECA of the French Arkema Group is Siliporite. The particle size of the molecular sieve powder is 0.7mm, 1.0mm, 1.3mm, 1.6mm, 2.0mm and other specifications. The main water-removing (water-absorbing, drying) agents that can be used in one-component and two-component polyurethane systems are Siliporite NK30AP and Siliporite SA1720, available in powder and paste product forms.



In the large two-component polyurethane system, molecular sieves can be added to the polyol/pigment filler mixture, but the impact of molecular sieves on pot life must be considered. SA1720 is a water absorbing agent specially developed for polyurethane systems, which improves the pot life of two-component polyurethane systems. Depending on the moisture in the system, adding 2% to 5% is sufficient to remove residual moisture.