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Polyurethane emulsion of defects and the processing method in use

by:Sinograce Chemical     2020-06-24
A, waterborne polyurethane resin storage happened technical problems and solving methods in the process of 1. 1 is stored in the process of condensation and viscosity rise ( 1) May is the cause of dispersant and wetting agent is not enough, or with some easy decomposition of dispersant, such as sodium tripolyphosphate, potassium, etc. The salt in the process of storage, easy to decompose, to cause pigment flocculation again. At this time should be added after adding some dispersant, of course, selection of dispersants, the application of different kinds and amount of dispersants, so as to avoid failure affect dispersion efficiency as dispersant. ( 2) Yan, stuffing improper selection, reactive ngan, packing, such as zinc oxide or titanium dioxide on filling. In principle, should not choose such pigments, fillers, one thousand presence of such substances, apply some special surfactant wetting system. ( 3) PH value, can also cause such problem. The deployment of buffer solution should be strengthened, control the dosage of the strong alkaline pigment, use some PH range of thickener. ( 4) Excessive organic solvents, such as film-forming polyurethane emulsion or ethylene, propylene glycol dosage is too large. Should reduce the dosage of the organic solvent, choose some polyurethane emulsion film with high efficiency. 1. Decrease in viscosity in the process of storage (2 1) Thickener by bacteria or enzyme degradation, some thickening agents such as HEC, is the nutrition of bacteria, if there is bacterial decomposition of the thickener, the viscosity is reduced. Therefore, improve the conditions of corrosion or without HEC thickening system. ( 2) PH value they drift away from thickener optimal scope of work. Alkali swelling thickening agent, such as ASE series, are sensitive to PH, optimum PH range between 9 ~ 10, if choose ammonia adjust PH value, for ammonia volatile, resulting in decreased PH, the thickener efficiency is reduced. Therefore, choose the AMP - 95 kinds of organic alkali PH regulator or use the PH less sensitive to changes of thickener. 1. 3 freeze-thaw instability ( 1) The amount of film forming of polyurethane emulsion are too high. As high efficiency of film-forming polyurethane emulsion is adopted such as Tg PPH or lower the dosage of the emulsion film and the polyurethane emulsion. ( 2) The amount of antifreeze is not enough. Should increase the dosage of the glycol. ( 3) Not appropriate surfactant system. Few people pay attention to such reason. If the freezing and thawing flocculation, increase the amount of surfactant; If the freezing and thawing coalescence, or viscosity rise, will increase the amount of surfactant with glycol, or increase the dosage of protecting glue, or increasing the dosage of the three at the same time. 1. 4 color change
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