Summary of the invention
The object of the present invention is to provide preparation method high deacetylized, a kind of chitosan of high-molecular weight.
The present invention includes following steps:
1) shrimp shell pre-treatment: fresh prawn shell is rinsed well, and oven dry is pulverized, and sieves, and promptly gets the shrimp shell after sieving;
2) calcium salt is removed in acid treatment: the shrimp shell after will sieving soaks with excessive hydrochloric acid, filters, and collects the shrimp shell, cleans, and removes hydrochloric acid remaining in the shrimp shell, promptly gets the shrimp shell after the deliming;
3) alkaline purification removes Deproteinization: the shrimp shell after the deliming with excessive sodium hydroxide solution immersion, is cooled off, filter, collect the shrimp shell, clean, remove residue sodium hydroxide in the shrimp shell, promptly get except that the shrimp shell behind the albumen;
4) remove astacin: will soak in potassium permanganate solution except that the shrimp shell behind the albumen, filter, filtration product is soaked in sodium sulfite solution, filter, clean, drying promptly gets chitin;
5) acetyl is taken off in alkaline purification: chitin is soaked with excessive sodium hydroxide solution, and cooling is filtered, and the cleaning and filtering product is removed residue sodium hydroxide, and oven dry promptly gets chitosan.
In step 1), the described mesh size that sieves can be 100~150 μ m.
In step 2) in, the volume ratio of shrimp shell and hydrochloric acid can be 1 during described the immersion: (5~10), the mass concentration of described hydrochloric acid can be 5%~15%, and the time of described immersion can be 4~6h.
In step 3), the volume ratio of shrimp shell and sodium hydroxide solution can be 1 during described the immersion: (5~10), the mass concentration of described sodium hydroxide solution can be 10%~20%, and described immersion can be soaked 1~2h under 80~90 ℃ of temperature.
In step 4), the mass concentration of described potassium permanganate solution can be 2%~5%; The described time that will soak in potassium permanganate solution except that the shrimp shell behind the albumen can be 0.5~1h, and the mass concentration of described sodium sulfite solution can be 5%~10%, and the described time that filtration product is soaked in sodium sulfite solution can be 0.5~1h.
In step 5), the mass concentration of described sodium hydroxide solution can be 40%~45%, described chitin be can be with the condition that excessive sodium hydroxide solution soaks: temperature is 90~110 ℃, soaks each 2~4h 1~2 time; Before the described oven dry, can wash by water filtration product, remove residue sodium hydroxide, clean at least 1 time with dehydrated alcohol again.
The preparation method of a kind of chitosan of the present invention compared with prior art has the following advantages:
1) the shrimp shell after will pulverizing uses the screen cloth in 100~150 μ m apertures to sieve, and makes the time of deliming shorten, and can improve the molecular weight of product chitosan.
2) in removing the step of astacin, because potassium permanganate has strong oxidizing property, the energy degrade chitosan, therefore, the soak time that shortens potassium permanganate and sodium bisulfite can improve the molecular weight of chitosan.
3) in the step of taking off the acetyl step, use the alkali interrupter method to take off acetyl step by step, to influencing the experiment condition of deacetylating degree of chitosan, viscosity-average molecular weight, temperature of reaction (T), reaction times (t), naoh concentration (C
NaOH), study by orthogonal design, find that each factor to the influence of deacetylation is in proper order: t>T>C
NaOHInfluence to viscosity-average molecular weight is in proper order: C
NaOH>T>t takes all factors into consideration the processing condition that obtain optimum, makes the deacetylating degree of chitosan for preparing reach 91%~93%, and viscosity-average molecular weight is 8.9 * 10
5~94 * 10
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Embodiment
Embodiment 1
1) prepare raw material: with fresh prawn shell clean dry, pulverizer is pulverized then, crosses the sub-sieve in 150 μ m apertures, promptly gets the shrimp shell after sieving;
2) calcium salt is removed in acid treatment: the shrimp shell after will sieving soaks 4h with excessive hydrochloric acid under agitation condition, filters, and collects the shrimp shell, and water thoroughly cleans, and removes hydrochloric acid remaining in the shrimp shell, promptly gets the shrimp shell after the deliming;
3) alkaline purification removes Deproteinization: the shrimp shell after the deliming is stirred under 90 ℃ of temperature with 10% excessive sodium hydroxide solution soak 2h, cooling is filtered, collection shrimp shell, and water thoroughly cleans, and removes residue sodium hydroxide in the shrimp shell, promptly gets except that the shrimp shell behind the albumen;
4) remove astacin: will in 2% potassium permanganate solution, under agitation condition, soak 0.5h except that the shrimp shell behind the albumen, filter, and wash with water to filtrate limpid till, this moment, filter residue was a purple, again filter residue is soaked 0.5 in 5% sodium sulfite solution under agitation condition, filter, water washes repeatedly guarantees that sodium bisulfite cleans up, 60 ℃ of dryings promptly get chitin;
5) take by weighing the dried chitin of 3g and pack in the there-necked flask, with 40%NaOH in 90 ℃ of reaction 1h, room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, at 90 ℃ of reaction 1h, the room temperature cooling is filtered with 40%NaOH, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash twice with dehydrated alcohol again, the dry chitosan that gets.The gained deacetylating degree of chitosan is 85.38%, and viscosity-average molecular weight is 1.01 * 10
6
The measuring method of deacetylation: acid base titration
Get 3 parts of 0.3~0.5g chitosans, place the 250ml triangular flask, standard salt acid solution 30ml with 0.1mol/L, stir down at 20~25 ℃, dissolve (but adding distil water) therebetween fully until chitosan, add 6 indicator (tropeolin-D-aniline blue (volume ratio 1: 2)) then, become pale bluish green to solution with the free H+ of the standard caustic soda solution titration of 0.1mol/L.Other gets a duplicate samples, dries to constant weight at 105 ℃, measures 3 times, calculates water ratio (W).
Deacetylation (D.D.%)=203n/ (Q+42n)
N=C
1V
1-C
2V
2(C wherein
1, V
1Be respectively the concentration and the volume of hydrochloric acid, C
2, V
2Be respectively concentration sodium hydroxide and volume)
The Q=sample quality * (1-W).
Viscosity-average molecular weight adopts this area progressively dilution method commonly used to measure.
Embodiment 2
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 40%NaOH at 100 ℃ of reaction 1.5h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, react 1.5h at 100 ℃ with 40%NaOH, the room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times the dry chitosan that gets again with dehydrated alcohol.The gained deacetylating degree of chitosan is 89.19%, and viscosity-average molecular weight is 8.91 * 10
5
Embodiment 3
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 40%NaOH at 110 ℃ of reaction 2h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, react 2h at 110 ℃ with 40%NaOH, the room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times the dry chitosan that gets again with dehydrated alcohol.The gained deacetylating degree of chitosan is 95.2%, and viscosity-average molecular weight is 8.74 * 10
5
Embodiment 4
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 45%NaOH at 90 ℃ of reaction 1.5h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, react 1.5h at 90 ℃ with 45%NaOH, the room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times the dry chitosan that gets again with dehydrated alcohol.The gained deacetylating degree of chitosan is 88.76%, and viscosity-average molecular weight is 9.43 * 10
5
Embodiment 5
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 45%NaOH at 100 ℃ of reaction 2h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, react 2h at 100 ℃ with 45%NaOH, the room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times the dry chitosan that gets again with dehydrated alcohol.The gained deacetylating degree of chitosan is 93.62%, and viscosity-average molecular weight is 9.38 * 10
5
The infared spectrum of chitosan shows (referring to Fig. 1): the carbonyl peak (1655cm of acid amides
-1) very weak, the N-H peak (1599cm of the amino of chitosan
-1) very strong, acid amides becomes amino behind the chitin deacetylase, and amino peak is strong, the deacetylating degree of chitosan height.
The x-ray diffraction pattern of chitosan (referring to Fig. 2): chitosan locates to occur peak crystallization at 10.9 ° and 20.1 °, near the crystalline hydrate structure of the corresponding chitosan of the diffraction peak of angle of diffraction 2 θ 10.9 °, near the II shape crystalline texture of the corresponding chitosan of the diffraction peak 21.1 °.Bibliographical information (Samuels RJ.Solid state characterization of the structure of chitosan films[J] Polym.Sci.Polym.Phys.Ed, 1981,19 (7): 1081-1087), raising along with deacetylation, the I type structure of chitosan will change II type structure gradually into, and the order of structure improves.Illustrate that prepared chitosan of the present invention is mainly II type structure, and absorption peak is sharp-pointed, has good crystalline structure.
Embodiment 6
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 45%NaOH at 110 ℃ of reaction 1h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, in the cooling of 110 ℃ of reaction 1h room temperatures, filter with 45%NaOH, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times with dehydrated alcohol again, the dry chitosan that gets.The gained deacetylating degree of chitosan is 89.63%, and viscosity-average molecular weight is 9.07 * 10
5
Embodiment 7
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 50%NaOH at 90 ℃ of reaction 2h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, in the cooling of 90 ℃ of reaction 2h room temperatures, filter with 50%NaOH, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times with dehydrated alcohol again, the dry chitosan that gets.The gained deacetylating degree of chitosan is 90.29%, and viscosity-average molecular weight is 8.58 * 10
5
Embodiment 8
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 50%NaOH at 100 ℃ of reaction 1h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, in the cooling of 100 ℃ of reaction 1h room temperatures, filter with 50%NaOH, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times with dehydrated alcohol again, the dry chitosan that gets.The gained deacetylating degree of chitosan is 89.36%, and viscosity-average molecular weight is 8.92 * 10
5
Embodiment 9
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 50%NaOH at 110 ℃ of reaction 1.5h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, reinstall in the there-necked flask, react 1.5h at 110 ℃ with 50%NaOH, the room temperature cooling, filter, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times the dry chitosan that gets again with dehydrated alcohol.The gained deacetylating degree of chitosan is 91.11%, and viscosity-average molecular weight is 74 * 10
5
Embodiment 10
The preparation method of chitin is identical with embodiment 1, take by weighing the dried chitin of 3g and pack in the there-necked flask, with 45%NaOH at 100 ℃ of reaction 4h, the room temperature cooling is filtered, and the thorough cleaning and filtering product of water, remove residue sodium hydroxide, wash 2 times, the dry chitosan that gets with dehydrated alcohol.The gained deacetylating degree of chitosan is about 80%, and viscosity-average molecular weight is 6.8 * 10
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