微晶纤维素在季铵碱水溶液中的低温溶解研究

Low temperature dissolution of microcrystalline cellulose in quaternary ammonium base aqueous solution

选用四甲基氢氧化铵(TMAH)、四乙基氢氧化铵(TEAH)、四丙基氢氧化铵(TPAH)3种季铵碱水溶液为溶剂,通过低温冷冻、室温解冻溶解微晶纤维素(MCC),研究不同温度及不同溶剂浓度下MCC的溶解效果,对不同季铵碱水溶液处理后的MCC的溶解行为进行表征。结果表明:随着冻融温度的降低,3种溶剂中MCC的溶解度整体上均呈现先上升后慢慢趋于稳定的趋势;在不同溶剂体系下,随着季铵碱浓度的增大,MCC的溶解度均呈现上升趋势;当冻融温度为-30℃、溶剂中季铵碱质量分数为35%时MCC的溶解效果最佳,在TMAH、TEAH和TPAH水溶液中MCC的溶解度分别为1.2%、11.5%和7.25%;季铵碱水溶液体系为MCC的非衍生化溶剂体系,其中TEAH能够削弱MCC内部氢键,溶解能力最强;经TEAH、TPAH处理的MCC的结晶度均下降,其中TEAH溶胀处理后MCC的结晶度由63.11%下降到43.71%,TEAH溶解后再生MCC的结晶度下降到30.46%,MCC的晶型由纤维素I晶型转变为纤维素II晶型;3种季铵碱水溶液中TEAH去结晶能力最强,对MCC的溶解效果最好。

Three kinds of quaternary ammonium base aqueous solutions,namely tetramethylammonium hydroxide(TMAH),tetraethylammonium hydroxide(TEAH)and tetrapropylammonium hydroxide(TPAH),were selected as solvents to dissolve microcrystalline cellulose(MCC)through low-temperature freezing and room-temperature thawing.The dissolution effect of MCC was studied at different temperatures and solvent concentrations,and the dissolution behavior of MCC treated with different quaternary ammonium base aqueous solutions was characterized.The results showed that the solubility of MCC in all three solvents showed an overall trend of first increasing and then gradually stabilizing as the freeze-thaw temperature decreased;the solubility of MCC showed an increasing trend with the increase of quaternary ammonium base concentration in different solvent systems;the dissolution effect of MCC was optimized when the freeze-thaw temperature was-30℃and the mass fraction of quaternary ammonium base was 35%in the solvent,and the solubility of MCC in TMAH,TEAH and TPAH aqueous solutions was 1.2%,11.5%and 7.25%,respectively;the quaternary ammonium base aqueous solution system was a non-derivative solvent system for MCC,in which TEAH could weaken the internal hydrogen bonds of MCC and offer the strongest solubility;the crystallinity of MCC treated with TEAH and TPAH both decreased,the crystallinity of MCC decreased from 63.11%to 43.71%after TEAH swelling treatment,and the crystallinity of regenerated MCC decreased to 30.46%after TEAH dissolution,and the crystal form of MCC transformed from cellulose crystal formⅠto cellulose crystal formⅡ;and TEAH had the strongest ability to decrystallize and contributed the best dissolution effect to MCC among the three quaternary ammonium base aqueous solutions.