Methods Of Improving The Properties Of Polyurethane Resins

Waterborne polyurethane has many advantages, so it is widely used in coatings, inks, adhesives, leather finishing agents, artificial leather, gloves lubricants and so on.

Take leather finishing agent as an example: finishing is an important part in leather manufacturing.

It can increase the appearance and durability of leather, improve the grade, increase variety and expand the scope of use.

Among them, polyurethane coating agents have good film forming properties, strong covering power, strong adhesion, excellent physical properties of coatings, and can greatly improve the grade of leather making.

At present, most of the waterborne PU are mainly prepared by self emulsifying method. The PU containing hydrophilic group is the main curing component. When the film is dried, if the hydrophilic component can not effectively enter the crosslinking network, the film formed by drying will be swollen with water.

In addition, it lacks the crosslinking density and high molecular weight that can be obtained from two-component solvent based PU film. Therefore, the water dispersoid coating has poor water resistance, solvent resistance, heat resistance and luster, which severely limits its use.

Therefore, the crosslinking density of the coating is often used to improve the water resistance of the emulsion coating.

There are two commonly used crosslinking methods: one is to synthesize polyhydroxyl compounds with a function of more than 2 when the PU prepolymer is synthesized, and to directly generate cross-linked PU prepolymer. The prepolymer can be well dispersed in water, and the chain is formed to form macromolecules, and finally the emulsion is formed.

This method is also called pre crosslinking. The disadvantage is that the viscosity of the prepolymer can be increased, and it is difficult to disperse in water, which will affect the stability of the emulsion.

In recent years, the research on screening and synthesis of new crosslinking agent and multifunctional chain extender is quite active. It has become one of the main ways to improve the physical and mechanical properties and water resistance of waterborne PU.

The other way is to use the anionic PU emulsion with carboxylic acid as crosslinking agent. The cross-linking reaction takes place on the carboxyl group of PU molecule, with nitropropane, carbonimide and metal salt compounds, and cross-linking at room temperature.

This kind of crosslinking agent is usually added when using PU emulsion, because its crosslinking reaction rate is very fast, gel is broken in a short time.

The foreign joint method can successfully solve the problem of hydrophilicity of PU emulsion coating, but because of the addition of crosslinking agent, the two component finishing agent can cause inconvenience to the construction. This method is used less.

Now we introduce a series of modified silicone resin to polyurethane leather, polyurethane finishing agent, polyurethane adhesive, shoe sole, polyurethane coating and ink. Through the contrast test of the engineers, we find that the existing PU and oil-based PU products can be solved.

The products are introduced as follows: 1. Adhesive: the series of products are modified organosilicon crosslinking agents, which can enhance the adhesion between different substrates and polyurethane coating materials for synthetic leather, so as to enhance the finishing and adhesion, and at the same time bring about the feeling of hydrolysis resistance and smoothness.

It can replace toxic multi nitrogen propanedipine cross linking agent.

Two. Wetting agent: this series of products is designed to improve the wettability between polyurethane coating materials and polyurethane coating materials and different substrates. It can also be used as foam modifier and leveling agent for polyurethane synthetic leather.

Three. Pore forming agent: this series of products is mainly used to improve the myogenic properties of the coatings, thereby improving the final touch and surface fluidity of leather.

The products are hydroxyl free and can be used as an effective wetting agent and pore forming agent.

Four, leveling agent: this series of products can give polyurethane synthetic leather surface smoothness.

In wet process, the surface moisture permeability and levelness of bass are improved. In dry process, PU leather is tacky and silky.

Five, bubble regulator: this series of products is designed for bubble control in the process of wet polyurethane sizing, and the cellular structure is vertical to the uniform circular pass.

At the same time, it also has antifoaming effect, providing smooth skin or bass layer.

Six, PU resin modifier: this series of products contains active groups, polyether terminated or hydroxyl terminated silicone modifiers, which can directly participate in slurry synthesis reaction, also can be added as functional additives, give polyurethane synthetic leather Beth and surface better moisture permeability, permeability, better low temperature flexibility, better anti viscosity, higher wear resistance, good surface smoothness, foam stability or excellent processability.

At the same time, it has good compatibility with polar solvents, non-polar solvents, polyols and isocyanates.