Reagents: propylene oxide, sodium hydroxide, isopropanol, acetone, anhydrous B.
Alcohol, hydrochloric acid, ammonium sulfate and calcium chloride are all analytically pure, and chitosan (CTS,
D.d = 92.7% 1 (Nantong Xingcheng biochemical company).
Instruments: pH DZ-2 pen acidity meter, 72 1A spectrophotometer.
Meter, 170SX Fourier transform infrared spectrometer (Nicolet company 1.
Synthesis of 1.2 hydroxypropyl chitosan
Mixing a certain amount of chitosan and isopropanol for 30 minutes, adding
50% NaOH aqueous solution, alkalized and stirred for 60 minutes, and sealed overnight. Time magazine.
Days, add catalyst and stir well, and add a certain amount of propylene oxide.
React at room temperature for 60 min in a stirred reactor, and then react at a certain temperature.
React at 0℃ for a certain time, then adjust the pH to neutral and disperse in B.
In alcohol/water solution, after continuous stirring and suction filtration, it is repeatedly soaked and washed with acetone.
After washing, a dry product is obtained for later use.
1_3 test
Molecular mass. 2 1; Degree of substitution [13,141; Infrared characterization: hydroxypropyl chitosan
After refining, CTS and HPCTS were mixed with KBr and made into tablets with Fu.
Determination by vertical leaf transform infrared spectrometer; Solubility: dissolve 0.5g HP CTS.
Stir in 20 mL distilled water for a certain time, and observe its content in water.
Dissolve feelings; Moisture absorption and moisturizing performance. 6 1
2 Results and discussion
2. 1, 1.
Synthesis of 1.2 hydroxypropyl chitosan
Mixing a certain amount of chitosan and isopropanol for 30 minutes, adding
50% NaOH aqueous solution, alkalized and stirred for 60 minutes, and sealed overnight. Time magazine.
Days, add catalyst and stir well, and add a certain amount of propylene oxide.
React at room temperature for 60 min in a stirred reactor, and then react at a certain temperature.
React at 0℃ for a certain time, then adjust the pH to neutral and disperse in B.
In alcohol/water solution, after continuous stirring and suction filtration, it is repeatedly soaked and washed with acetone.
After washing, a dry product is obtained for later use.
1_3 test
Molecular mass. 2 1; Degree of substitution [13,141; Infrared characterization: hydroxypropyl chitosan
After refining, CTS and HPCTS were mixed with KBr and made into tablets with Fu.
Determination by vertical leaf transform infrared spectrometer; Solubility: dissolve 0.5g HP CTS.
Stir in 20 mL distilled water for a certain time, and observe its content in water.
Dissolve feelings; Moisture absorption and moisturizing performance. 6 1
2 Results and discussion
2. 1 Effect of reaction conditions on degree of substitution
2. 1. 1 temperature
It can be seen from the table 1 that with the increase of reaction temperature, the degree of substitution Ds is the first.
The reason is that the higher the reaction temperature, the greater the infiltration between reactants.
The more thorough the penetration and collision between propylene oxide and reactive groups of reactants,
Speed up the reaction, side reactions will also occur, and propylene oxide
Low boiling point is volatile, and too high temperature is unfavorable to the main reaction, leading to substitution.
The reaction temperature is 60℃.
Table 1 Effect of reaction temperature on products
Note: the reaction time is 8 h, chitosan is 2 g, propylene oxide is 20 mL, and the catalyst is 1 mL. ..
2. 1.2 propylene oxide dosage
It can be seen from Table 2 that the degree of substitution of the product increases with the increase of the amount of propylene oxide.
The reason is that increasing the amount of reactants can increase the reaction direction.
The internal diffusion speed of chitosan, and there are enough raw materials and chitosan.
The active groups of chitosan react, adding reaction reagents and chitosan molecules.
The collision probability of surface active groups increases the degree of substitution, although it can be achieved by
By increasing the amount of propylene oxide to improve the degree of substitution of products, but in production
Cost should also be considered in production, so the final requirements should prevail.
In order to choose the appropriate dosage, the dosage of propylene oxide was selected in this experiment.
It's 20 ml.
Table 2 Effect of propylene oxide dosage on products
Note: the reaction was carried out at 60℃ for 8 h, chitosan 2 g, catalyst 1 ml.
2. 1.3 times
As can be seen from Table 3, the longer the reaction time, the higher the degree of substitution and solubility of the product.
The reaction between chitosan and propylene oxide is solid-liquid heterogeneous.
Phase reaction, the initial stage of the reaction is the diffusion, penetration and alkali shell of propylene oxide.
The homogeneous mixing stage of polysaccharide is followed by propylene oxide and chitosan.
The reaction groups react, and the product changes from swelling to dissolution.
The extension of time makes the reaction more complete, and the alkaline chitosan will penetrate water.
The function of diffusion is to react with reactive groups. most
After that, prolonging the reaction time can let "diffusion-reaction-swelling-dissolution" pass.
This repetition makes the reaction more complete, the degree of substitution increases and the product dissolves.
The performance has been improved. Therefore, the water-soluble product can be obtained after 8 h of reaction.
Table 3 Effect of reaction time on products
Note: reaction temperature is 60℃, chitosan is 2 g, propylene oxide is 2ml, and catalyst 1 mL. ..
2. 1.4 Other conditions
Alkalization with isopropanol as solvent can ensure the uniform distribution of alkaline aqueous solution.
Powder is a good dispersant. Heat released during alkalization
Uniform dispersion, easy transfer, and reduced hydrolysis and transformation of alkaline chitosan.
More uniform alkaline chitosan was obtained by reaction. In addition, the solubility of alkali in alcohol
The solubility is lower than that in water, so chitosan can absorb more alkali.
Isopropanol can also improve the reaction activity and uniformity.
The reaction between chitosan and propylene oxide is heterogeneous, but adding
The phase transfer catalyst can increase the contact opportunity between propylene oxide and chitosan,
Increasing the conversion of propylene oxide is beneficial to the reaction.
3 Conclusion
The product with good solubility was prepared by the reaction of propylene oxide with chitosan.
Chitosan derivatives with properties. Increase reaction raw materials and reaction time
Prolongation is beneficial to the improvement of product substitution degree, while increasing reaction temperature is beneficial to the improvement of product substitution degree.
So that the degree of substitution of the product first increases and then decreases. FvrIR of products and raw materials
Infrared spectrum shows that the molecular chain of modified chitosan (mainly in c _
Hydroxypropyl was substituted by 1 on OH. Compared with raw material CTS,
The modified product HPCTS has good solubility, hygroscopicity and moisture retention.
It increases with the increase of degree of substitution. Water-soluble chitosan and its derivatives
Widely used in textile, food, medicine, daily cosmetics and many other fields.
The application prospect is broad.