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At present, most of the waterborne PUs are mainly prepared by self-emulsification method. The main curing component is PU containing hydrophilic groups. When the coating film is dried, if the hydrophilic component cannot effectively enter the cross-linked network, the coating film formed by drying will be encountered. Water swells easily. In addition, it lacks the crosslink density and high relative molecular mass that can be obtained with a two-component solvent-based PU coating, and thus the water resistance, solvent resistance, heat resistance, and gloss of these aqueous dispersion coating films are poor. Limited the scope of its use. Therefore, it is often used to increase the crosslinking density of the coating film to improve the water resistance of the emulsion coating film. There are two commonly used cross-linking methods: one is the synthesis of PU prepolymers, the addition of polyhydroxyl compounds with a functionality greater than two, direct cross-linked PU prepolymers, and good dispersion of the prepolymers in water. , And chain extension to form macromolecules, the final formation of emulsion.
This method is also called the pre-crosslinking method. The disadvantage is that it tends to increase the viscosity of the prepolymer and it is difficult to disperse in water and affect the stability of the emulsion. In recent years, the research on the screening and synthesis of novel cross-linking agents and multifunctional chain extenders has been active, and has become one of the main ways to improve the physical mechanical properties and water resistance of aqueous PUs. Another method is the diplomatic linkage method. An anionic PU emulsion with carboxyl groups is used for cross-linking. The cross-linking reaction takes place on the carboxyl group of the PU molecule, and aziridine, carboimide, and metal salt compounds are performed at room temperature. Cross-linked. Such a cross-linking agent is generally added when a PU emulsion is used, because the cross-linking reaction rate is fast, and a gel is generated and broken in a short time. The diplomatic alliance method can successfully solve the hydrophilicity problem of PU emulsion coating, but due to the addition of cross-linking agent, the two-component finishing agent is inconvenient for construction, and this method is less used.
We now introduce a series of modified silicone resins into polyurethane leathers, polyurethane finishing agents, polyurethane adhesives, shoe soles, polyurethane coatings, and inks. Through the comparative tests of engineers, we have found that we can solve current water-based PUs and oil-based PUs. There are various problems with the product. This series of products are introduced as follows:
The series of products are modified silicone cross-linking agents, which can enhance the adhesion between different substrates and polyurethane coating materials for synthetic leather, thereby improving the coating properties and adhesion, and at the same time bring about hydrolysis resistance and smoothness. feel. Instead of the toxic polyaziridine cross-linking agent.
Second, wetting agent:
This series of products is designed to improve the wettability between polyurethane coating materials and between polyurethane coating materials and different substrates. It can also be used as a cell regulator and leveling agent for polyurethane synthetic leathers.
Third, the homogenizer:
This series of products is mainly used to increase the muscle formation of the coating, thereby improving the final touch and surface fluidity of the leather. This series of products does not contain hydroxyl groups and can be used as an effective wetting agent and a homogenizer.
Fourth, leveling agent:
This series of products can give polyurethane synthetic leather surface smoothness. In the wet process, the surface moisture permeability and leveling of bass are improved; in the dry process, PU leather is improved in anti-adhesion and has a silky feel.
Fifth, cell regulator:
This series of products is designed for the cell control during the wet polyurethane slurry leather process. The cell structure is vertically long to uniform. At the same time there is defoaming, providing a smooth skin or bass layer.
Sixth, PU resin modifier:
This series of products contain active groups, polyether-terminated or hydroxyl-terminated silicone modifiers, which can directly participate in the slurry synthesis reaction and can also be added as functional additives, giving the polyurethane synthetic leather bass and surface better Moisture permeability, air permeability, better low temperature flexibility, better anti-adhesion, higher wear resistance, excellent surface smoothness, cell stability or excellent processability. It also has good compatibility with polar solvents, non-polar solvents, polyols, and isocyanates.
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