Study On The Properties Of Quaternary Ammonium Hydrolyzed Surfactants For Plant Protein

Surfactant is an indispensable chemical product in industrial production and daily life.At present,most of the surfactants we use are non-renewable petrochemical products,which have certain ecological toxicity,bioaccumulation and low biodegradability,so they do great harm to the environment.Under the strategic background of circular economy,"carbon neutralization"and"carbon peak",it has become an urgent task to develop a green surfactant with biodegradability and renewability.In recent years,hydrolyzed vegetable protein,as a by-product of agricultural processing,is considered to be an ideal raw material for green surfactants.However,when used as surfactants,directly hydrolyzed plant proteins inevitably have some performance defects,such as poor surface properties,poor antibacterial properties,low solubility and so on,which usually need to be improved by chemical modification.At the same time,the structure of hydrolyzed vegetable protein is complex,so it is difficult to accurately predict the structure-property relationship of hydrolyzed vegetable protein after chemical modification.Therefore,using a variety of hydrolyzed vegetable proteins as raw materials,a series of quaternized hydrolyzed vegetable protein surfactants with different structures were synthesized by ring-opening addition reaction of epoxy groups and amino groups,and the relationship between structure and properties was studied comprehensively and systematically.The main contents of this paper are as follows:1.Study on the optimum synthesis path and properties of epoxypropyl alkyl quaternary ammonium saltEpoxy propyl dodecyl dimethyl ammonium chloride（EPDDAC）was synthesized by nucleophilic substitution reaction of dodecyl dimethyl tertiary amine（DDA）and epichlorohydrin（ECH）.The effects of solvent type,solvent content,reaction temperature and reaction molar ratio on the purity of the product werinvestigated.The optimum synthesis conditions were obtained as follows:methanol（60%）as solvent and reaction temperature 20℃.The molar ratio of tertiary amine to epichlorohydrin is 1:2.Under these conditions,three kinds of green tertiary amines with alkyl chain length between C₈～C₁₆ were selected to synthesize a group of epoxy propyl alkyl quaternary ammonium salts with different alkyl chain length.The products were characterized by nuclear magnetic resonance spectroscopy（NMR）and Fourier transform infrared spectroscopy（FT-IR）to verify the synthesis of the products.Through the tests of surface tension and foam properties,it was found that the surface activity,foam stability and foaming property of epoxy propyl alkyl quaternary ammonium salt increased with the increase of alkyl chain length.2.Synthesis of quaternary ammonium hydrolyzed vegetable protein surfactantsHydrolyzed wheat protein-based surfactants with different quaternization degrees were synthesized from hydrolyzed wheat protein and epoxy propyl lauryl dimethyl ammonium chloride by changing the feed ratio.The characterization results of FT-IR show that the structure of the product is correct.The amino content was tested by formaldehyde titration,the result shows that when the feed ratio of hydrolyzed wheat protein to quaternary ammonium salt was 1:20,the amino conversion rate of the product was close to 100%,indicating that the quaternization of hydrolyzed wheat protein reached saturation.At the same time,under this feed ratio,a series of quaternized hydrolyzed vegetable protein surfactants with different molecular weight,hydrophobic chain length and kinds of hydrolyzed vegetable protein were synthesized.the amino content of the surfactant was tested,and it shows that the amino conversion was close to 100%.3.Study on properties and application of quaternary ammonium hydrolyzed vegetable protein surfactantsBy testing the surface tension and foam properties of hydrolyzed vegetable protein raw materials and 12 kinds of quaternized hydrolyzed vegetable protein surfactants,it was found that quaternization could significantly improve the surface activity,foaming and foam stability of hydrolyzed vegetable protein.The foaming and foam stability of protein-based surfactants increased with the increase of the degree of quaternization,the molecular weight of hydrolyzed protein and the length of hydrophobic chain.The decrease of molecular weight and the increase of alkyl chain length of hydrolyzed protein can optimize its surface activity.However,the surface activity indexes of protein-based surfactants with different degree of quaternization showed different trends.with the increase of the degree of quaternization,the critical micelle concentration decreased at first and then increased,the surface tension decreased gradually,whereas all the parameters of adsorption increased.But generally speaking,the increase of quaternization degree is beneficial to the improvement of surface activity and foam performance.Due to the structure and properties of hydrolyzed protein,quaternized hydrolyzed wheat protein has the best surface activity,and quaternized corn protein has the best foam performance.Finally,through the test of fiber specific resistance and pure bending,proved that quaternized hydrolyzed wheat protein can effectively improve the antistatic and flexibility of the fabric,and the best concentration of finishing solution is 5 g/L.