CN111995772B

CN111995772B - Preparation method of silk-polymer mixed solution

Info

Publication number: CN111995772B
Application number: CN202010948844.4A
Authority: CN
Inventors: 谢海波; 岳旺; 邓璐璐; 陈鹏
Original assignee: Guizhou University
Current assignee: Guizhou University
Priority date: 2020-09-10
Filing date: 2020-09-10
Publication date: 2023-04-18
Anticipated expiration: 2040-09-10
Also published as: CN111995772A

Abstract

The invention discloses a preparation method of a silk-polymer mixed solution, which comprises the following steps: degumming a silk raw material to obtain a product A; (2) Mixing carboxylic acid compound and organic amine to form proton type ionic liquid to obtain product B; (3) Adding product A and polymer into product B at total mass concentration of 0.1-25%, stirring and dissolving at 50-140 deg.C for 10-360 min to obtain fibroin ionic liquid solution, i.e. silk-polymer mixed solution. The method has the characteristics of simple treatment process, low ionic liquid cost, recoverability of the ionic liquid and high dissolving efficiency.

Description

Preparation method of silk-polymer mixed solution

Technical Field

The invention relates to a silk treatment method, in particular to a preparation method of a silk-polymer mixed solution.

Background

With the current increasingly exhausted fossil energy and the environmental problems caused by fossil energy, people pay more attention to the development and utilization of natural polymer materials.

Silk is a high-quality protein fiber and consists of two parts of sericin and silk fibroin. The composite material has excellent physical properties, porous property, good air permeability, excellent moisture absorption performance, good mechanical property, biocompatibility and physical stability, the application range of the composite material is expanded to the novel fields of food, medicine, regenerative medicine, cosmetology and the like, and the composite material has wide application prospect and high application value.

Since the fibroin is used in the novel field, the silk dissolution and reprocessing are essential steps. The fibroin molecular chains are linked by a large number of hydrogen bonds within the fiber and form a regular high crystalline structure, and thus only limited swelling occurs in water and most organic solvents without dissolution. In order to obtain the regenerated silk protein solution, the selection of a proper solvent and a proper dissolving process are crucial, and the solvent and the dissolving process not only ensure the sufficient dissolution of the silk, but also avoid the excessive degradation of the silk, thereby meeting the requirements of subsequent processing and application. At present, the silk dissolution systems developed mainly include two major types, inorganic salt systems and organic salt systems. The inorganic salt system is represented by high-concentration LiBr aqueous solution and CaCl ₂ The solvent system needs high-concentration salt to dissolve the silk under the condition of temperature rise, the process flow is long, the process is complicated, a large amount of salt, water and time are consumed, the fibroin molecular chain is seriously degraded, and the industrial application of the silk is limited. The organic salt is a new silk fiber dissolving system developed in recent years, and mainly comprises N-methyl-N-morpholine-N-oxide (NMMO) and ionic liquid.

The ionic liquid is a salt which is in a liquid state at or near room temperature and is completely composed of anions and cations, and is also called low-temperature molten salt. The ionic liquid is widely applied as an organic solvent with better dissolving performance and is not separated from the green environmental protection performance of the ionic liquid, the dissolving rate of the ionic liquid is higher, the solvent can be recycled after being used, and the environmental pollution is hardly caused. Compared with the traditional organic or inorganic solvent, the ionic liquid has more excellent physical and chemical properties, and the solvent ionic liquid is not only applied to the field of dissolving high molecular polymers, but also has important influence and wide application in the fields of biology, chemistry and materials. The ionic liquid is divided into alkylated quaternary ammonium salt ionic liquid and proton type ionic liquid. The alkylated quaternary ammonium salt ionic liquid has the disadvantages of complex preparation process, higher price, high recycling cost and the like, and is always subject to scaling. The proton type ionic liquid is prepared by directly equimolar reacting organic acid, inorganic acid and organic amine, has the characteristics of simple preparation process, low price, distillability, recycling and the like, and is recently attracted by attention.

The ionic liquid can destroy the hydrogen bond structure between natural protein polymers, and the more interference on the fibroin, the higher the solubility of the fibroin in a solvent. In 2004, it was found that the ionic liquid can dissolve silk and spider silk in the process of preparing a spider silk protein and silk fibroin composite film layer by F, junghans and the like. Phillips and the like research the dissolving characteristic of the 1-butyl-3 methylimidazolium chloride ionic liquid to silk, and provide a new idea for exploring a new technology of protein processing; mantz et al dissolved silk fibroin with different ionic liquids, and found that the highest solubility of silk fibroin in 1-ethyl-3 methylimidazolium chloride ionic liquid reaches 23.3% at 100 ℃; in 2008, zhu Hailin and the like use 1-allyl-3-methylimidazolium chloride as a silk fibroin solvent, and the conclusion that the two are both good silk fibroin solvents is obtained; 2010 Yan Guoliang and the like discuss the dissolution and regeneration characteristics of silk fibroin in ionic liquid, and the ionic liquid with different anions and cations has great influence on the solubility of silk fibroin, and indicate that Cl ^- The solubility to silk fibroin is maximal for the anion, and this conclusion is verified experimentally. Zhang Huihui, etc. by using 1-butyl-3 methylimidazolium chloride as solvent, preparing 10% spinning solution under the heating condition of 100 ℃, using methanol as coagulating bath, preparing regenerated silk fibroin by dry-wet spinning method, dissolving silk fibroin by ionic liquid,and the regenerated fibroin/water-soluble polyurethane blend membrane is prepared, and the prepared blend membrane has good hydrophilicity and biological stability and is insoluble in water. Through literature and patent search, reports of dissolving silk by using imidazole quaternary ammonium salt ionic liquid as a solvent are provided, such as CN102153766A, CN104693457A, CN105061788A, CN102011212A, CN108034057A. However, imidazole quaternary ammonium salt is known to have the defects of higher ionic liquid price, separation and purification, high regeneration cost and high fibroin solution viscosity. According to literature and patent search, no report is provided so far that silk is dissolved by using cheap proton type ionic liquid and a mixed solvent consisting of the proton type ionic liquid and a polar solvent.

To sum up, the cheap proton type ionic liquid and the mixed solvent composed of the proton type ionic liquid and the polar solvent are used for dissolving the silk, so that the reasonable recycling of resources can be realized, the waste raw materials can be regenerated, and the method has important application value and industrial application prospect.

Disclosure of Invention

The invention aims to provide a preparation method of a silk-polymer mixed solution. The method has the characteristics of simple treatment process, low ionic liquid cost, recoverability of the ionic liquid and high dissolving efficiency.

The technical scheme of the invention is as follows: a method for preparing silk-polymer mixed solution comprises the following steps:

(1) Degumming the silk raw material to obtain a product A;

(2) Mixing carboxylic acid compound and organic amine to form proton type ionic liquid to obtain product B;

(3) Adding product A and polymer into product B at total mass concentration of 0.1-25%, stirring and dissolving at 50-140 deg.C for 10-360 min to obtain fibroin ionic liquid solution, i.e. silk-polymer mixed solution.

In the preparation method of the silk-polymer mixed solution, the degumming treatment is to put the silk raw material into the sodium bicarbonate solution with the concentration of 0.3-0.7wt% and boil for 40-80min, and then wash and dry the silk raw material by deionized water.

In the above method for preparing a silk-polymer mixed solution, the carboxylic acid compound and the organic amine are mixed in a molar ratio of 1:1 and mixing.

In the preparation method of the silk-polymer mixed solution, the product B further contains a polar organic solvent, wherein the carboxylic acid compound, the organic amine and the polar organic solvent are mixed in a molar ratio of 1:1: x is mixed, wherein X is more than 0 and less than or equal to 4.

In the preparation method of the silk-polymer mixed solution, the polar organic solvent is one or a mixture of any two or more of dimethyl sulfoxide, dimethyl amide, diethyl amide, gamma valerolactone, ethylene carbonate and propylene carbonate.

In the preparation method of the silk-polymer mixed solution, the silk material in the step (1) is one or a mixture of any two or more of mulberry silk, tussah silk, castor-oil plant silk and tussah silk.

In the preparation method of the silk-polymer mixed solution, the carboxylic acid compound in the step (2) is one or a mixture of any two or more of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, beta-hydroxypropionic acid and levulinic acid; the organic amine is one or a mixture of any two or more of n-butylamine, di-n-butylamine, dihydroxyethylamine, tributylamine, triethanolamine, tetramethylguanidine, 1,5-diazabicyclo [4.3.0] -5-nonene (DBN), 1,8-diazabicycloundecene-7-ene, triazabicyclo and 4-dimethylamino pyridine.

In the preparation method of the silk-polymer mixed solution, the polymer is one or a mixture of any two or more of cellulose, chitin, chitosan, polyacrylonitrile, polylactic acid, polyethylene terephthalate or polycaprolactone.

In the preparation method of the silk-polymer mixed solution, the mixing mass ratio of the product A and the polymer in the step (3) is 1:9-9:1.

the application of the silk-polymer mixed solution prepared by the method in the preparation of silk protein-polymer composite regenerated fibers, regenerated gels and regenerated composite films.

The invention has the advantages of

1. In the process, the ionic liquid does not need a special separation and purification process, compared with the traditional process of adopting the ionic liquid containing the imidazole quaternary ammonium salt as a solvent, the process disclosed by the invention directly mixes the carboxylic acid compound and the organic amine or the carboxylic acid compound, the organic amine and the polar organic solvent, and then mixes the mixture with degummed silk, so that the one-pot method for preparing the silk solution is realized, and the process has the advantage of simple preparation process.

2. Compared with the traditional ionic liquid, the ionic liquid provided by the invention has the advantages that the raw materials are easy to obtain, the preparation process is simpler, and the cost of the ionic liquid solution is greatly reduced, so that the preparation cost of the silk solution is reduced.

3. After the silk solution is prepared, the ionic liquid solution can be easily recovered and reused, so that the waste of resources is greatly reduced, the emission of pollutants is reduced, and the silk solution is more environment-friendly.

4. The process can treat various silks, and the silk dissolving efficiency is high.

Drawings

FIG. 1 is a graph showing the apparent viscosity and shear rate of 5wt% silk/cellulose solutions prepared in examples I, II, III and IV;

FIG. 2 is a rheological graph of loss modulus G 'and storage modulus G' versus angular frequency for silk/cellulose solutions of 5wt% different blending ratios prepared in examples one, two, three, and four;

Detailed Description

The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention.

Examples of the invention

The first embodiment is as follows:

(1) Degumming mulberry silk, boiling with 0.5wt% sodium bicarbonate solution for 60min, washing with deionized water, and air drying;

(2) Weighing 0.75g of degummed silk, cutting into 2cm small segments, weighing 0.75g of cotton pulp cellulose, tearing into small pieces by using forceps, and fully drying;

(3) Weighing 13.8g of levulinic acid and 14.7g of 1, 5-diazabicyclo [4.3.0] -5-nonene (DBN), fully mixing in a flask, and placing in an ice bath for low-speed stirring;

(4) And (3) dissolving the cotton pulp cellulose and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 100 ℃, and the silk/cellulose solution with the blending ratio of 5:5 is obtained after stirring at low speed for 40 min.

The influence of different kinds of silk on the reaction (table 1, numbers 1-4) was compared under the same conditions, and as shown in table 1, the results showed that the mulberry silk has the highest dissolubility mass concentration; the influence of different types of carboxylic acid on silk dissolution is examined under the same reaction condition (table 1, serial numbers 1 and 5-11), and the result shows that the stronger the acidity, the better the silk dissolution effect; the effect of different types of organic bases on silk dissolution is compared under the same conditions (table 1, serial numbers 1 and 12-20), and the result shows that the stronger the alkalinity of the organic bases, the better the silk dissolution effect; the solvent is favorable for reducing the viscosity of the fibroin solution (table 1, number 1, 21-26), and the dissolving efficiency in the high-polarity solvent is higher; the influence of temperature on the reaction is examined under the same reaction conditions (table 1, number 1, 27-31), and the results show that the silk dissolving efficiency tends to increase along with the increase of temperature, and the dissolving efficiency is reduced when the temperature exceeds 140 ℃; under the same reaction conditions, the maximum dissolved mass concentration also tends to increase along with the prolonging of the reaction time (Table 1, no. 1, 32-38), and the maximum mass concentration of the silk does not increase after 240 minutes of reaction; further experiments showed that the dissolution efficiency showed a tendency to decrease with increasing reaction time. The effect of different polymers on silk dissolution was examined under the same reaction conditions (table 1, no. 1, 39-44), with the highest maximum mass fraction of silk-cellulose mixed solution soluble.

Table 1: influence of different reaction conditions on the preparation of the Silk-Polymer Mixed solution

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Example two:

(2) Weighing 0.3g of degummed silk, cutting into 2cm small sections, weighing 1.2g of cotton pulp cellulose, tearing into small pieces by using forceps, and fully drying;

(3) Weighing 13.8g of levulinic acid and 14.7g of 1, 5-diazabicyclo [4.3.0] -5-nonene (DBN), fully mixing in a flask, and stirring at a low speed in an ice bath;

(4) And (3) dissolving the cotton pulp cellulose and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 8:2, wherein the dissolving temperature is 100 ℃, and the silk/cellulose solution with the blending ratio of 8:2 is obtained after stirring at low speed for 40 min.

Example three:

(2) Weighing 1.2g of degummed silk, cutting into 2cm small segments, weighing 0.3g of cotton pulp cellulose, tearing into small pieces with forceps, and fully drying;

(4) And (3) dissolving the cotton pulp cellulose and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 2:8, wherein the dissolving temperature is 100 ℃, and the silk/cellulose solution with the blending ratio of 2:8 is obtained after stirring at low speed for 40 min.

FIG. 1 is a graph showing the apparent viscosity and shear rate of silk/cellulose solutions prepared in examples I, II and III at different blending ratios of 5 wt%. Referring to fig. 1, in the silk/cotton pulp blended solution prepared according to the technical scheme provided by the invention, the apparent viscosity decreases with the increase of the shear rate, and the characteristic of shear thinning is shown.

FIG. 2 is a rheological graph of loss modulus G 'and storage modulus G' of silk/cellulose solutions prepared in examples one, two and three and having different blending ratios of 5wt% and angular frequency. Referring to fig. 2, in the fibroin solution and the silk/cellulose blended solution prepared according to the technical scheme provided by the invention, the angular frequency range corresponding to G '> G' can qualitatively represent the entanglement degree in the solution system, and the higher the solution concentration is, the stronger the interaction between macromolecules is, and the more serious the entanglement is. As the concentration increases, G "and G', respectively, increase, the value of ω at the intersection of the two curves progresses toward a lower value. This is probably due to the fact that the high concentration results in the formation of a temporary entangled network, which requires a longer relaxation time for the high concentration silk/cellulose solution.

Example four:

(1) Degumming castor bean, boiling with 0.5wt% sodium bicarbonate solution for 60min, washing with deionized water, and air drying;

(2) Weighing 0.75g of degummed silk, cutting into 2cm small sections, weighing 0.75g of chitosan, and fully drying;

(3) Weighing 11.8g of propionic acid and 16.7g of 1, 5-diazabicyclo [4.3.0] -5-nonene (DBN), fully mixing in a flask, and placing in an ice bath for low-speed stirring;

(4) And (3) dissolving the chitosan and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 100 ℃, and the silk/chitosan solution with the blending ratio of 5:5 is obtained after stirring at low speed for 40 min.

Example five:

(2) Weighing 0.75g of degummed silk, cutting into 2cm small sections, weighing 0.75g of chitin, and fully drying;

(3) Weighing 7.5g of acetic acid and 21.0g of 1, 8-diazabicycloundecen-7-ene (DBU), fully mixing in a flask, and placing in an ice bath for stirring at a low speed;

(4) And (3) dissolving the chitin and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 100 ℃, and stirring at a low speed for 40min to obtain the silk/chitin solution with the blending ratio of 5:5.

Example six:

(1) Degumming castor bean silk, boiling with 0.5wt% sodium bicarbonate solution for 60min, washing with deionized water, and air drying;

(2) Weighing 0.75g of degummed silk, cutting into 2cm small sections, weighing 0.75g of polylactic acid, and fully drying;

(4) And (3) dissolving the polylactic acid and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 120 ℃, and the silk/polylactic acid solution with the blending ratio of 5:5 is obtained after stirring at a low speed for 80 min.

Example seven:

(2) Weighing 0.3g of degummed silk, cutting into 2cm small segments, weighing 1.2g of cotton pulp cellulose, tearing into small pieces with forceps, and fully drying;

(3) Weighing 12.6g of levulinic acid and 15.9g of 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU), fully mixing in a flask, and stirring in an ice bath at a low speed;

(4) And (3) dissolving the cotton pulp cellulose and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 80 ℃, and stirring at a low speed for 100min to obtain the silk/cotton pulp cellulose blending solution with the blending ratio of 5:5.

Example eight:

(4) And (3) dissolving the chitosan and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 5% of the blending ratio of 5:5, wherein the dissolving temperature is 140 ℃, and the silk/chitosan blending solution with the blending ratio of 5:5 is obtained after stirring at a low speed for 120 min.

Example nine:

(1) Degumming mulberry silk, boiling with 0.3wt% sodium bicarbonate solution for 80min, washing with deionized water, and air drying

(3) Levulinic acid, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), and dimethyl sulfoxide were weighed out in a molar ratio of 1:1:0.1, fully mixing in a flask, and placing in an ice bath for low-speed stirring;

(4) And (3) dissolving the chitin and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 0.1% of the blending ratio of 1:9, wherein the dissolving temperature is 140 ℃, and stirring at a low speed for 10min to obtain the silk/chitin blending solution with the blending ratio of 1:9.

Example ten:

(1) Degumming natural silk, boiling with 0.7wt% sodium bicarbonate solution for 40min, washing with deionized water, and air drying;

(2) Weighing 0.75g of degummed silk, cutting into 2cm small sections, weighing 0.75g of polylactic acid, tearing into small pieces by using forceps, and fully drying;

(3) Levulinic acid, 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and propylene carbonate were weighed out in a molar ratio of 1:1:4 mixing, fully mixing in a flask, placing in an ice bath, and stirring at a low speed

(4) And (3) dissolving the polylactic acid and the degummed silk in the step (2) in the ionic liquid in the step (3) at the mass concentration of 25% of the blending ratio of 9:1, wherein the dissolving temperature is 50 ℃, and stirring at a low speed for 360min to obtain the silk/polylactic acid blending solution with the blending ratio of 9:1.

The above description is only for the purpose of illustrating the present invention and the appended claims, and the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.

Claims

1. A preparation method of a silk-polymer mixed solution is characterized by comprising the following steps:

(1) Boiling silk material in 0.3-0.7wt% sodium bicarbonate solution for 40-80min, washing with deionized water, and drying to obtain product A;

(2) Mixing a carboxylic acid compound and an organic amine according to a molar ratio of 1:1, mixing to form proton type ionic liquid to obtain a product B; the product B also contains a polar organic solvent, wherein the molar ratio of the carboxylic acid compound to the organic amine to the polar organic solvent is 1:1: x is mixed, wherein X is more than 0 and less than or equal to 4;

(3) The mixing mass ratio of the product A to the polymer is 1:9-9:1, adding the product A and a polymer into the product B according to the total mass concentration of 0.1-25%, stirring and dissolving for 10-360 minutes at 50-140 ℃ to obtain a silk protein ionic liquid solution, namely a silk-polymer mixed solution;

the polar organic solvent is one or a mixture of any two or more of dimethyl sulfoxide, dimethyl amide, gamma valerolactone, ethylene carbonate or propylene carbonate;

the polymer is one or a mixture of any two or more of cellulose, chitin, chitosan, polyacrylonitrile, polylactic acid, polyethylene terephthalate or polycaprolactone.

2. The method for preparing silk-polymer mixed solution according to claim 1, characterized in that: the silk raw material in the step (1) is one or a mixture of any two or more of mulberry silk, tussah silk, castor-oil plant silk or tussah silk.

3. The method for preparing silk-polymer mixed solution according to claim 1, characterized in that: the carboxylic acid compound in the step (2) is one or a mixture of any two or more of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, beta-hydroxy propionic acid and levulinic acid; the organic amine is one or a mixture of any two or more of n-butylamine, di-n-butylamine, dihydroxyethylamine, tributylamine, triethanolamine, tetramethylguanidine, 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-diazabicycloundecen-7-ene, triazabicyclo and 4-dimethylaminopyridine.

4. Use of the silk-polymer mixed solution prepared according to the method of any one of claims 1 to 3 for preparing silk protein-polymer composite regenerated fibers, regenerated gels and regenerated composite films.