Synthesis And Characterization Of Castor Oil-Modified And Ambient Self-crosslinked Polyurethane Dispersions

Polyurethane dispersion(PUD) coating is applied on hard substrate, which needs high water resistance, ethanol resistance, hardness, heat resistance, glossiness and low costs. However, the comprehensive properties and costs of PUD in the current market are often difficult to achieve the ideal application requirements.To solve the above problems, a new type of functional monomer containing ketone groups, 2,2-bis(4-(2-hydroxypropoxy levulinate)phenyl)-propane(BHLPP), is prepared by using 2,2-bis(4-(2,3-epoxypropoxy)phenyl)-propane(BEPP) and levulinic acid(LA). Using the BHLPP as chain extender, adipic dihydrazide(ADH) as latent crosslinking agent, poly-neopentylene adipate glycol(PNA), 4,4-methylenedicyclohexyl diisocyanate(HMDI), and dimethylolpropionic acid(DMPA) as main materials, ambient self-crosslinked PUDs are synthesized, expecting to improve water resistance, ethanol resistance, hardness and heat resistance of PUD films. Castor oil(CO) modified and ambient self-crosslinked PUDs are also synthesized by using low price, polyfunctionality, containing unsaturated double bond CO to replace a part of PNA, expecting to reduce costs and improve water resistance and glossiness of PUD films.The BHLPP is separated and purified by the method of extraction, thin layer chromatography(TLC) and column chromatography. The structure of the BHLPP is characterized by FT-IR and NMR. The results showed that using 6:1 ethyl acetate/petroleum ether as an elution to purify the BHLPP, the conversion of the BHLPP reaches about 95%. The structure of the BHLPP is assured by FT-IR and NMR.The ambient self-crosslinked PUDs have excellent stability. The average particle size of PUDs are at 50~155nm and exhibite bimodal distribution. TEM analysis shows that the particle of PUDs exhibite regular spheroid morphology. During film formation, the self-crosslinking reaction between ketone(-CO-) of BHLPP and hydrazine(-NHNH2) of ADH has really reacted. Meanwhile, when the ratio of n(-NHNH2)/n(-CO-) is 0.75:1, the comprehensive properties of PUD film is best. As the BHLPP content increases, the crosslinking density, hardness, water resistance, ethanol resistance, heat resistance and glass transition temperature(Tg) of PUD films are significantly improved.The structure of the CO modified and ambient self-crosslinked PUD films are characterized by FT-IR. The transmission electron microscopy(TEM) and particle size analysis show that the particle of PUDs exhibite regular spheroid and bimodal distribution. As the value of R increases, the water and ethanol absorptions of PUD films reduce and the hardness of PUD films increases; As DMPA content increases, the average particle size of the PUDs reduces and the stability of the PUDs increases, but the water absorption of the PUD films increases; The viscosity of PUDs increases with the increase of CO content. However, the stability of PUDs reduces with the increase of CO content. As CO content increases, the glossiness and heat resistance of the PUD films increase and the water and ethanol absorptions of PUD films reduce; As BHLPP content increases, the crosslinking density and hardness of the PUD films increase and the water and ethanol absorptions of PUD films reduce. When the value of R, DMPA content, CO content and BHLPP content are 1.8, 24mmol·(100g resin)-1, 13.5g·(100g resin)-1 and 12.9g·(100g resin)-1, respectively, the synthetic castor oil-modified and ambient self-crosslinked PUD has excellent glossiness, water resistance, ethanol resistance, hardness and heat resistance.