Studied On Synthesis And Properties Of Non-phosphate Detergent Builder-Layered Sodium Disilicates

Although pentasodium phosphate (STPP) was a detergent builder with good washing ability it was also one reason of which induce eutrophication in close or semi-close water area. So, to search a substitution of STPP is becoming ever important. Layered sodium disilicates (Na₂Si₂O₅) have good ion binding capacity, provide appropriate water alkalinity; and may cooperate with other composition in good method, They were considered as excellent non-phosphate detergent builder and have good prospect for substituting STPP.In this paper, some problems about layered sodium disilicates, such as, synthesis conditions, properties, bivalent ion binding mechanism, hydrolysis rules, etc, have been studied.When constant temperature was chosen between 630-800 °C, the synthesis conditions of layered sodium disilicates have been systemic researched by using sodium silicate (modulus =1.5-2.4)as source.The data proved that the phases of layered sodium disilicate can be obtained without any seed when the modulus of sodium silicate was from 2.1 to 2.2 and constant temperature was from 660-780°C. 5 layered sodium disilicate (content of 5 phase >80%) may be synthesized at 660-780°C for 2-8 minutes. The pure phase of δ-Na₂Si₂O₅ can be prepared at 720-750°C for 2-5 minutes by employing sodium silicate withmodulus=2.1-2.2 as source material. This is a new discovery because common preparing method of 5-Na2Si2Os is adding seed to accelerate the crystalline of 5-Na2Si2O5.By using mixture phase of 5-Na2Si205 and a-Na2Si205 as structure direct agent, the pure phase of a-Na2Si2Os was synthesized at 780 ± 10"C. This way may short the crystalline time and improve the purity of synthesized samples.The Ca2+ and Mg2+ ion binding properties of layered sodium disilicate were studied at 25-60°C. The data were compared with the properties of zeolite 4A, amorphous sodium silicate and sodium metasilicate. The experimental results proved that 5-Na2Si2Os had higher Mg"+ ion binding capacity than zeolite 4A did. In researched field (builder's concentration 0.1 -0:02%), Ca2+ ion binding capacity of 5-Na2Si205 increased with the decrease of builder's concentration. This was a different peculiarity to other builders.High stability 5-Na2Si205 has been prepared by adding Al element as framework stable agent and let it to enter the framework of 5-Na2Si;O5. The synthesized samples may keep as 5 phase and did not transformed into |3 phase after they were marinated in hot water (80±2°C) for 60 minutes. The method improved the framework stability of 5-Na2Si:O5. The experimental data proved that Ca2+ ion binding capacity of 5-Na2Si205 would decrease 30% after it was marinated in hot water (80 + 2 °C ) for 60 minutes;-' but, Ca2+ ion binding capacity of Al-5-Na2Si2O5 only decreased 5% through the same process. According to the XRD data of Al-5-Na2Si205, adding Al element may effectively restrict the form of a-Na2Si205. MAS NMR characterized the atom coordination of Al-5-Na2Si205. It was demonstrated that Al element existed in oxide and substituted the site of SiO2.In the experiments, the qualitative and quantitative methods have been found for measuring the stability of 5 layered sodium disilicate inpowder detergent's manufacture process. By above technology, the framework stability and dissolubility of Al-8-Na2Si205 were studied in the solution of Na2CO3, Na2SO4, water glass, and LAS. The experiments demonstrated that Na2CC>3 and water glass may accelerate the phase transformation of Al-5-Na2Si205 in hot water. LAS had not clear effect on the phase transformation of Al-5rNa2Si205. Na2SO4 may restrict the phase transformation of Al-5-Na2Si20s. It was proved that Al-5-Na2Si205 may keep as 5-Na2Si205 within two hours (65-70°C) in supersaturation solution ofNa2SO4.XRD, SEM, FT-IR and ion binding rate characterized the hydrolysis samples of 5-Na2Si20s from different solutions. The data showed that , in tap water, a part of 5-Na2Si20s transported to kanemite- a layered sodium silicate with ion exchange ability, another part of 8-Na2Si205 dissolved into water and formed deposit through bonding with Ca2+ and Mg2+. The data proved that the Rieck's conclusion about its ion binding process was incompletion; the process whicja 5-Na2Si205 removed divalent ions has the characteristic of ion exchange and precipitation.The manufacture of Al-5-Na2Si20s (10000 tons/year) had been achieved by referring the basic data from laboratory and employing suitable synthesis conditions. The product was soft and its apparent gravity was in 0.30-0.65. The content of 5-Na2Si205 in manufactured product was higher than that in current other products. It was proven that high stability Al-5-Na2Si205 (product name: HSST-l)had good application effect.