Chemical Industry: The role of water-based polyurethane resin in inks

First of all, let me introduce that water-based polyurethane resin is a type of polymer whose main chain contains -NHCOO- repeating structural units. It is polymerized by isocyanate (monomer) and hydroxyl compound. Because it contains a highly polar urethane group and is insoluble in non-polar groups, it has good oil resistance, toughness, wear resistance, aging resistance and adhesion. Materials suitable for a wide temperature range (-50–1500°C) can be made from different raw materials, including elastomers, thermoplastic resins and thermosetting resins. It is not resistant to hydrolysis at high temperatures and is not resistant to alkaline media. The polyurethane resin used in ink is generally formed by the reaction of polyester/polyether polyol and isocyanate, with a molecular weight of about 20,000 to 40,000. During the research and development process, alcohol ester solvents can be used to prepare corresponding benzene-free ink resins according to the environmental protection needs of ink factories and printing factories.

The functions of water-based polyurethane resin in inks are as follows:

1. Excellent yellowing resistance of water-based polyurethane resin

Polyurethane resin for ink is mainly synthesized from aliphatic polyester and aliphatic isocyanate as the main raw materials during the preparation process. Compared with aromatic polyurethane, It has excellent optical stability and the film has excellent yellowing resistance after film formation.

2. Water-based polyurethane resin for soft substrates Excellent adhesion and bending resistance

The molecular chain segment of polyurethane resin for ink contains polar groups such as urethane, allophanate, ester bond, ether bond, etc., and has various The polar groups on the surface of polar base materials such as PET and PA form hydrogen bonds, thereby forming joints with a certain connection strength. After the polyurethane resin is made into ink, it has good adhesion fastness when printed on the surface of polar plastic substrates.

3. Water-based polyurethane resin has good affinity with pigments

Polyurethane resins for wettability inks are generally composed of polyester or polyether polyols, alicyclic diisocyanates and diamine/diol chain extenders preparation. Due to the introduction of urea bonds in PU resin, polyurethane-urea resin (PUU) is formed, which makes it have good dispersion and wetting properties for pigments and good fullness.

4. Water-based polyurethane resin has good resin compatibility

Water-based polyurethane resin for ink has good compatibility with water-based acrylic resin, water-based epoxy resin, etc., and can be used according to the actual situation. Appropriately added to the process formula to improve the overall performance of the ink.

5. Excellent product film-forming properties of water-based polyurethane resin

Ink-based polyurethane resin is different in structure from polyurethane resins used in other fields. Traditional polyurethane mainly consists of polyester polyol/polyether polyol and isocyanate. The reaction generates hydroxyl-terminated polyurethane resin. The polar groups in the molecular structure are mainly urethane. The molecular cohesion is not enough to meet the film-forming performance requirements of the resin for ink. Therefore, the polyurethane resin for ink introduces urea group on the basis of traditional polyurethane. To greatly improve the cohesive strength and film-forming properties of the resin itself.

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