Solid content is an important indicator of waterborne polyurethane
solid content of the impact both in the drying process of the waterborne polyurethane film forming rate, also affect the cost of storage transport waterborne polyurethane, at the same time of high and low solid content of waterborne polyurethane as the raw material of product processing.
Currently limited to raw material types, preparation methods, such as complete sets of equipment condition limit, most domestic waterborne polyurethane is a hydrophilic group with carboxyl anionic waterborne polyurethane, relatively low solid content more concentrated in about 20 ~ 40%, it is difficult to achieve 50% above its solid content, more difficult to meet the needs of the market diversification.
So, the production of high solid content products (
Solid mass fraction 50%)
Is very positive and practical significance to promote the wide application of waterborne polyurethane, become the development direction of waterborne polyurethane emulsion and research hot spot.
The hydrophilic chain extender is an important influence factors of solid content of waterborne polyurethane.
Hydrophilic chain extender is in chain extender for polyurethane pre polymers at the same time, the hydrophilic groups into the main chain of such molecules.
Research indicates that kinds of chain extender, synthesis methods and selection of polyurethane raw materials are the key to influence the waterborne polyurethane emulsion solid content.
Containing carboxyl of water-borne polyurethane low solid content, viscosity, soft film;
Anionic sulfonic group and to the hydrophilic chain extender preparation of waterborne polyurethane with strong hydrophilicity, high crystallinity, the characteristic of high solid content, but there is also a reaction process is difficult to control, process equipment requirement is high, the film issue such as difference of resistance to water.
The above two kinds of hydrophilic group each have their advantages and disadvantages, waterborne polyurethane composite use can realize the complementary advantages, improve the performance of waterborne polyurethane and enlarge its application area.
So the same time sulfonic acid and carboxylic acid and two kinds of hydrophilic groups waterborne polyurethane has very practical significance.
Of waterborne polyurethane pre polymers before and after two hydrophilic chain extender, containing carboxylic acid and sulfonic acid groups of hydrophilic chain extender is introduced into the main chain of the polyurethane molecular up at the same time, the waterborne polyurethane as carboxylic acid, sulfonic acid type waterborne pu common characteristic, is easy to achieve high solid content of waterborne polyurethane, effectively avoid the sulfonic acid and carboxylic acid type waterborne polyurethane respective shortcomings, then through dendritic macromolecules of waterborne polyurethane modified high solid content, introducing dendritic macromolecules in the molecular structure of water-borne polyurethane, take advantage of dendritic macromolecule structure improves performance of the resin.
Study different hydrophilic radical effect on the properties of waterborne polyurethane emulsion, and dendritic macromolecules modified waterborne polyurethane resin of high solid content.
Sulfonic acid and carboxylic acid hydrophilic group through research on the influence of molecular structure and waterborne polyurethane emulsion performance, to the preparation of a kind of good physical and mechanical properties, water resistant, heat resistant, structure stable waterborne polyurethane resin of high solid content, which is based on the needs of the water-based synthetic leather processing technology, adopting waterborne polyurethane resin of high solid content through mechanical foaming principle, preparation of similar solvent-based polyurethane synthetic leather wet foam coating, to replace solvent-based wet coating processing technology.
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