Zeolite moisture scavengers are used in a variety of CASE applications, including polyurethane coatings, adhesives, sealants and elastomers. In polyurethane systems, trace moisture is one of the primary challenges in the manufacture of polyurethane products, which needs molecular sieve as a powerful moisture scavenger to solve it.
Why Moisture Scavenger Needed In Polyurethane System?
In the production of polyurethane, the most important chemical reaction is between isocyanates and polyols. As is known, the isocyanates are extremely sensitive to moisture, and even trace amounts of moisture will react with isocyanates to produce carbon dioxide, resulting in bubbling, poor adhesion and related problems.
As a chemical additive, moisture scavenger is a crucial component in polyurethane systems. It is designed to react with and remove moisture from the raw materials or the surrounding environment to prevent it from reacting with isocyanates in the polyurethane system.
Zeolite Molecular Sieve For Polyurethane Moisture Scavenger
Zeolite molecular sieve has excellent chemical stability, and itself will not react with the isocyanates or polyols. However, it can effectively and selectively adsorb trace moisture in typical polyurethane formulations, inhibit the occurrence of detrimental reactions.
Zeolite molecular sieve used as polyurethane moisture scavengers are usually in powder form, which is also called activated zeolite powder or molecular sieve activated powder. Type 3A, 4A, 5A, 13X activated zeolite powders, they have controllable pore sizes, good dispersibility and high specific surface area, and are capable of quickly adsorbing trace amounts of moisture.
Type 3A activated zeolite powder: the most commonly used, suitable for almost all polyurethane systems, because the 3Å pore size only absorbs water and does not adsorb polyols and catalysts, thus avoiding the loss of polyol and isocyanate components.
Type 4A activated zeolite powder: It has stronger water absorption than type 3A activated zeolite powder, but it is prone to absorb polyols or small molecule additives. So it is suitable for some rigid polyurethane foam systems or polyurethane systems that require extremely low water content.
Type 5A activated zeolite powder: Its pore size is even larger, and it is occasionally used in special polyurethane systems, such as rigid foams or systems with high chemical resistance requirements, but with a high risk of secondary adsorption.
Type 13X activated zeolite powder: It has the largest pore size and absorbs water most thoroughly, but is rarely used in conventional polyurethane except in some high-polarity solvent systems or in the preparation of special prepolymers.
CASE Applications Of Zeolite In Polyurethane Industry
Polyurethane coating and pigment: Construction coatings such as self-leveling floor coating, wood-flooring coating, wood putty, basement waterproofing, sports hall flooring, industrial floors, decorative floors, UV resistant coatings, liquid-applied roofing, concrete re-surfacing; Equipment coatings such as lathe coating, crane coating, pipeline coating, turbine coating; Transportation coatings such as aerospace equipment surface coating, automotive coating, ship or yacht coating, marine container coating, traffic paint, railroad re-spiking; Metallic pigment coatings such as aluminum paints, zinc-rich primers, and etc.
Polyurethane adhesive and sealant: Artificial turf grass, carpet tiles, edge sealants, railway ballastless track laying, epoxy–resins for electrical insulation applications, polysulfide and silicone system for the construction industry, windscreen adhesive, wood splicing adhesive, waterproof shoe adhesive, PVC material adhesive, plywood adhesive, book binding adhesive, Ink adhesive, adhesive for packaging composite film, and etc.
Polyurethane Elastomer: Shoe and clothing materials such as shoe soles and logos, PU-based clothing, waterproof and permeable materials; Medical materials such as operating bed air bags, chemically resistant silicone molds, hospital mattresses, ice packs, bandages, plasma bags, masks; Sports goods such as football surface and inner liner, snowboard, drinking bag, Inflatable bed; Industrial supplies such as trumpet drum paper rubber edge, waterproof strip, soundproof material, fireproof material; Electrical wire and cable outer sheath material, insulation and heat resistance material; Other materials such as car interiors, truck bed liners, phone buttons, computer keyboard, plastic inflatable toys, and etc.
Polyurethane Foam: Foam boards, foam plastics, foam mattresses, foam dressings, foam caulking agents.