| Waterborne polyurethane,which uses water as solvent,makes polyurethane prepolymer diffused into water.It has attracted the public attention and rapidly developed into one of the world’s favorite products in today’s increasing emphasis on environmental protection situation due to the fact that it contains no or very few organic solvents,which is harmless to human beings and the environment.The key to the synthesis of waterborne polyurethane is to connect a hydrophilic group or a hydrophilic structure to the polyurethane molecular chain.The chain extender itself contains certain characteristic groups.After being connected to the polyurethane molecular segment,the polyurethane has certain functions of the chain extender.Introducing cationic hydrophilic groups into the polyurethane structure can obtain cationic waterborne polyurethane,which leads to the yellow emulsion because of its ionic characteristics and poor mechanical properties.Through experiment,this paper describes the synthesis of a cationic chain extender with a tertiary amine group on the side chain of the molecular chain,and then synthesize cationic waterborne polyurethane.Change one reaction condition at a time,it optimized a new cationic chain extender N,N dimethyl-2-(dimethylol)butylamine.Waterborne polyurethanes with different molar amounts of hydrophilic chain extenders were synthesized in order to explore its effect on the performance of cationic waterborne polyurethane.The cation chain extender was characterized by nuclear magnetic resonance hydrogen spectroscopy and liquid-mass spectrometry.The performance of the synthesized new cation was explored and compared with the water-based polyurethane of N-methyldiethanolamine system.The main contents are as follows:(1)Synthesis and characterization of a new cationic chain extender N,N-dimethyl-2-(dimethylol)butylamineUnder high temperature and high pressure,cationic chain extender N,N-dimethyl-2-(dimethylol)butylamine was synthesized by the reaction between 2-ethyl-2-hydroxymethyloxetane and dimethylamine solution.To characterize its structure,a peak of each position in the structure of N,N-dimethyl-2-(dimethylol)butylamine appeared on the NMR hydrogen spectroscopy,and an extremely molecular peak with strong signal appeared at 162 on the LC / MS instrument.Change one reaction condition at a time,the synthesis process was explored.N,N-dimethyl-2-(Dimethylol)butylamine has the highest formation rate,which can reach 97%,under the situation of 4% of catalyst dosage,1: 5 molar ratio of 2-ethyl-2-hydroxyl-methyloxetane to dimethylamine and 180 ° C of reaction temperature.(2)Study on cationic waterborne polyurethanePreparation of Cationic Waterborne Polyurethaned by using N,N-dimethyl-2-(dimethylol)butylamine as the hydrophilic chain extender,and the impact of chain extender addition method and neutralization degree for the reaction were explored.Besides,N,N-dimethyl-2-(dimethylol)butylamine is used to synthesize waterborne polyurethane under mild conditions and stable waterborne polyurethane dispersion can be obtained by one-time feeding at 60 ℃,and stable aqueous polyurethane emulsion can be gotten at a neutralization ratio of 1: 3.The addition amount of N,N-dimethyl-2-(dimethylol)butylamine and the particle size of the waterborne polyurethane dispersion was explored and compared with the waterborne polyurethane dispersion properties of the MDEA system.The result shows that N,N-dimethyl-2-(dimethylol)butylamine,as a chain extender,has better dispersion properties.Through the study of the yellowing resistance,mechanical properties,water resistance and resistance for the two waterborne polyurethanes,the mechanical properties of the cationic waterborne polyurethane synthesized in the experiment are higher than the MDEA system,the yellowing resistance is significantly enhanced,and the heat resistance is also excellent through thermogravimetric analysis,but the water resistance is not as good as the waterborne polyurethane synthesized by MDEA. |
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