Cautionary Notes for the Use of Polyurethane Ink Binders

When using polyurethane ink binders (especially alcohol-soluble/ester-soluble types), the key points to control are moisture, solvents, compatibility, curing, substrate and storage. This is to avoid problems such as composite delamination, non-drying and poor adhesion. 

 

1. Strict control of moisture and active impurities: The binder contains hydroxyl groups. When exposed to active hydrogen substances such as water, alcohols, and amines, it will consume the curing agent - NCO, resulting in decreased composite adhesion and incomplete drying of the ink film. The moisture content of the solvents (ethyl ester, isopropanol) must be ≤ 0.2%, and water or alcohol/ amine additives must not be mixed in. The humidity of the printing environment should be ≤ 65%, and the corona discharge of the substrate (OPP, PET, NY) should meet the standards and be free from moisture to prevent the residual moisture from affecting the reaction. 

 

2. Solvent and dilution specifications: Preferentially use ester-based (ethyl ester) and alcohol-ester mixed solvents, with the alcohol content controlled at ≤ 8%. Dilute slowly and stir at low speed according to viscosity requirements to avoid introducing bubbles at high speed. Match the evaporation gradient to ensure thorough drying, with solvent residue ≤ 3mg/m², and prevent subsequent compounding from causing foaming and stratification. 

 

3. Curing agent and compatibility test: For two-component systems, the specific curing agent should be added in the prescribed ratio. Prepare the mixture on the spot and use it immediately, controlling the applicable period. It is strictly prohibited to mix with systems containing active hydrogen such as chlorinated polypropylene and epoxy. Before batch production, a small-scale test must be conducted to verify the compatibility with adhesives, pigments, and substrates. In the case of water boiling / steam boiling scenarios, the interlayer peel strength should also be tested. 

 

4. Storage and Operation Safety: Store in a sealed container in a cool and dry place (5-30℃), protected from light and fire. Avoid high temperatures and direct sunlight. Use up the contents as soon as possible after opening to prevent moisture absorption and deterioration. Take appropriate protective measures during operation and keep away from fire sources. Dispose of the waste solvents in a compliant manner.