Synthesis And Properties Of Phosphate Extended Surfactants

Potassium monododecyl phosphate（MAPK）is a green and mild surfactant with excellent foaming properties,good detergency,low degreasing capacity,and low irritation.Therefore,it is widely used in personal cleaning care products.However,its sodium salt is poorly water-soluble and hardly resistant to hard water,so its application is limited.The sodium monododecyl polyoxyethylene ether phosphate（MAEPNa）by ethoxylation has good water solubility and hard water resistance,but the introduction of polyethylene oxide（PEO）block leads to the new problem of carcinogenic dioxane,therefore it is urgent to solve the problem of green alternation of MAPK.The introduction of polypropylene oxide（PPO）blocks in surfactant molecules do not produce carcinogenic dioxane,so the eco-friendly products sodium alkyl polypropylene ether phosphate（C_cP_pP）may be better than that of MAEPNa.PPO blocks provide dynamic amphiphilicity and the rugby like structure which may be formed on the interface of C_cP_pP will give it excellent properties such as emulsification,wettability,and detergency.Also besides,whether the unique properties such as low stimulation of C_cP_p P could be maintained or even better than that of MAPK needs to be further studied.In order to solve the above problems,a series of alkyl polypropylene ethers（C_cP_pP）（c=12,14,16,and 18,p=3,6,and 9）were synthesized by propoxylation of natural fatty alcohols,and then a series of sodium mono-alkyl polypropylene ether phosphate（MC_cP_pP）were synthesized by reaction with pyrophosphoric acid.The structures were characterized by FT-IR,ESI-MS,¹H-NMR,and ³¹P-NMR.Physicochemical properties and application properties such as Krafft point,surface tension,foam property,emulsification,wettability,electrolyte resistance,lime soap dispersing power,detergency,irritation,and primary biodegradability were determined,and the comparison with conventional surfactants MAPK,SDS,and SLE₃S were also further investigated.On this basis,the synthesis of C_cP_pP with phosphorus pentoxide as a phosphorylation agent was explored,which laid the foundation for the industrialization of C_cP_p P.The main results were shown as follows:（1）A series of C_cP_p were prepared by the propoxylation of fatty alcohol and propylene oxide with the KOH catalyst.Then,a series of MC_cP_PP were synthesized by the phosphorylation with pyrophosphoric acid and following neutralization.The calculated adduct number of PO（p）from the integral value of active hydrogen in ¹H-NMR of C_cP_pP was consistent with that from hydroxy value.C_c P_pP was monoalkyl phosphate by double indicator method of bromocresol green-phenolphthalein,which was consistent with the chemical shift of only mono-phosphate in ³¹P-NMR.The products were MC_cP_pP by the phosphorylation of C_c P_pP and pyrophosphoric acid.The structures of MC_cP _pP were further confirmed by FT-IR and ESI-MS.（2）The Krafft points of series MC_cP_pP were less than 0℃,indicating that it had good low-temperature water solubility.The electrolyte resistance of MC_cP_p P was significantly better than that of MAPK,and increased with the decrease of alkyl carbon chain number（c）and p.The MC₁₂P_pP had good hard water resistance which made it possible to be used alone in the formulation of daily chemicals.The outstanding salt resistance showed its special application potential.The surface tension(γ_cmc)of MC_cP_pP were lower than that of MAPK,and decreased with the increase of c.The cmc of MC_cP_pP was 1～3 orders of magnitude lower than that of MAPK,SDS,and SLE₃S which indicated that MC_cP_pP were easier to form micelle.The PC₂₀and CMC/C₂₀ of MC_cP_p P were higher than that of MAPK,SDS,and SLE₃S,indicating that MC_c P_pP was more inclined to adsorb in the gas-liquid interface.The shape factors（S）of MC_c P_pP were all more than 5,indicating that it also had the unique Rugball-like structure of extended surfactants.Other properties of MC_cP_pP such as foamability,emulsification,and wettability were also superior to that of MAPK.Especially MC₁₂P₃P had excellent properties such as medium foam property,low irritation,and excellent emulsification.Therefore,MC_cP_pP could replace MAPK as a new green and mild surfactant for personal care and toiletry.In addition,the emulsification of MC_cP_pP in silicone oil,jojoba oil,and Caprylic/Capric triglyceride was good,which showed that it had the potential to be used as a novel of green and mild cosmetic emulsifier.（3）C_cP_p P with a high content of MC_c P_pP was designed and synthesized by the two-step method of adding water.The results showed that the optimum conditions for the synthesis of high MC_cP_p P content by two-step water addition method were as follows:n(C₁₂P₃):n（P₂O₅）:n（H₂O）was 2:1:0.75,the reaction temperature was 80℃,reaction time was 8 h,water content for hydrolysis was 4 wt%,hydrolysis temperature was 90℃,hydrolysis time was 12 h.The results showed that the content of MC₁₂P₃P,DC₁₂P₃P,PA were 77.4 wt.%,12.9 wt.%and3.5 wt.%,respectively,and the conversion of C₁₂P₃ was 91.3%.