| Builder is an essential ingredient in laundry detergents,whose primary role is sequestering hardness ions to improve washing performance.Sodium tripolyphosphate(STPP)is recognized as the most cost-effective detergent builder.However,phosphorus resources are not rich in China and phosphates contribute to the problem of “eutrophication”.Present phosphate substitutions,small molecule carboxylates,zeolites,crystalline layered silicates and polycarboxylates,have their limitations in the application.Therefore,it is still a worthy of research to find cost-effective phosphate substitutes.Sodium oxalate is a dicarboxylic acid chelating agent,which can soften water by forming insoluble salts with polyvalent ions.Sodium oxalate as detergent builder has been explored in early patents.However,the cost of sodium oxalate is relatively high,so it is not applied in detergent products.With the development of industrial technology,the current technology for producing sodium oxalate with industrial exhaust gas can effectively reduce the production cost of sodium oxalate,providing an opportunity for sodium oxalate as a detergent builder.In this paper,after analysis of the basic physical and chemical properties,toxicological properties and biodegradability of sodium oxalate,sodium oxalate systematic research work was carried out.Traditional builders of sodium tripolyphosphate and 4A zeolite were conducted on the same washing conditions.The main research contents and conclusions are as follows:(1)First,the basic properties of sodium oxalate as a detergent builder were studied,including the calcium removal capacity,calcium removal rate of sodium oxalate,and the effects on surfactants wetting,emulsifying,foaming and washing performance.Compared with 4A zeolite and STPP,sodium oxalate has higher calcium removal capacity and faster removal rate.It also helps to improve the detergency of surfactants.(2)Stain removal performance is the most important property of detergents.The detergency of sodium oxalate in detergent formulations was further studied in this paper.The detergency performance of detergents with sodium oxalate as a detergent builder was studied from multiple angles,by adjusting the composition of the detergent formulation,washing time and temperatures,STPP and 4A zeolite also carried out on the same washing conditions.The experimental results show that t The experimental results show that the detergency of sodium oxalate-based detergents is close to that of STPP,and far superior to the phosphate-free builder 4A zeolite.(3)Enzymes are an important component of modern detergents,and small amounts of enzymes can effectively improve the ability to remove specific stains.In order to study the compounding performance of sodium oxalate and enzyme in the washing formula,protease,lipase and cellulase were respectiviely added to the sodium oxalate detergent formula,and the detergency of the corresponding stained cloth was measured and compared with STPP and 4A zeolite.The experimental results show that sodium oxalate and enzyme show better compounding performance than that of STPP and 4A zeolite.The reason is that sodium oxalate has little effect on the activity of the enzyme,which maintains the vitality of the enzyme in the detergent and produces better detergency performance.(4)As sodium oxalate removes hard water ions by precipitation,the generated insoluble oxalate may deposit on the fabric to produce ash.Ash deposition can cause the fabric "incrustation" and make the clothes yellow and hard.In this paper,sodium oxalate-based detergent formulations were conducted by adjusting the types of anionic surfactants and polymers.Cotton,polyamide and polyester fiber were chosen to study ash deposition by circulation washing.Experimental results find that cotton fabric is more likely to cause ash deposition than synthetic fabric.Through the screening of detergent formulations,three formulations with low ash content and high whiteness retention on three fabrics were obtained: methyl ester sulfonates(MES)/sodium carboxymethyl cellulose(CMC),MES/polyvinyl pyrrolidone(PVP)and alcohol ether sulfates(AES)/CMC.(5)The ash deposition mechanism of sodium oxalate detergents was studied by anionic surfactant and sodium oxalate formulation system.The zeta potential of insoluble oxalate and cotton fabric was determined in different surfactant solutions and the interaction force between them was calculated by Derjaguin–Landau–Verwey–Overbeek(DLVO)theory.The results show that when calcium oxalate phase is same in the surfactant solution,the deposition decreases as the maximum total interaction energy increases.(6)Significant factors of sodium oxalate detergent formulas were analyzed with statistical methods.The formulation of sodium oxalate detergent with AES as anionic surfactant and CMC as anti-deposition agent was screened by using the Plackett-Burman design method.It can provide a reference for further optimization.The results show that the improvement effect of sodium oxalate on the washing performance is extremely significant and significant respectively,especially for the washing performance of protein stained cloth and sebum stained cloth.The added amount of sodium oxalate within a relatively large range,the difference in ash content do not reach a level of significant impact. |
