阅读说明：本技术 一种聚离子液体改性的疏水型热塑型淀粉及其制备方法 (Polyion liquid modified hydrophobic thermoplastic starch and preparation method thereof ) 是由 夏于旻 汪菁晶 梁源 刘洁 张雯雯 赵忠政 梁娇娇 丁丹宁 吕晓洁 于 2019-09-11 设计创作，主要内容包括：本发明公开了一种聚离子液体改性的疏水型热塑性淀粉及其制备方法。所述热塑性淀粉包括玉米淀粉及聚离子液体。制备方法为：将玉米淀粉和聚离子液体分别溶于二甲基亚砜中,然后混合,加热并搅拌；将混合物烘干除去二甲基亚砜,得到固体产物；对固体产物加热熔融后压制成膜,得到热塑性淀粉膜。Poly[ECH-MIM]-DBS可与玉米淀粉形成新的氢键作用,使得淀粉处于无定形状态而具有热塑性。此外,原先亲水的玉米淀粉在聚离子液体Poly[ECH-MIM]-DBS的增塑下表现为疏水性,这一定程度上可以减少由于亲水对热塑性淀粉材料性能的影响,拓展了热塑性淀粉材料的应用。(the invention discloses polyion liquid modified hydrophobic thermoplastic starch and a preparation method thereof. The thermoplastic starch comprises corn starch and polyion liquid. The preparation method comprises the following steps: respectively dissolving corn starch and polyion liquid in dimethyl sulfoxide, mixing, heating and stirring; drying the mixture to remove dimethyl sulfoxide to obtain a solid product; and heating and melting the solid product, and pressing to form a film to obtain the thermoplastic starch film. Poly [ ECH-MIM ] -DBS can form new hydrogen bonding with corn starch, so that the starch is in an amorphous state and has thermoplasticity. In addition, the original hydrophilic corn starch is presented with hydrophobicity under the plasticization of the polyion liquid Poly [ ECH-MIM ] -DBS, so that the influence of hydrophilicity on the performance of the thermoplastic starch material can be reduced to a certain extent, and the application of the thermoplastic starch material is expanded.)

1. A polyion liquid modified hydrophobic thermoplastic starch is characterized by comprising corn starch and polyion liquid, wherein the mass ratio of the corn starch to the polyion liquid is (1.0-9.0): 1, wherein the polyionic liquid is Poly [ ECH-MIM ] -DBS.

2. the polyionic liquid modified hydrophobic thermoplastic starch of claim 1, wherein the polyionic liquid has the chemical formula:Wherein n is 50-5000.

3. the method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 1 or 2, characterized by comprising the steps of:

Step 1): respectively dissolving corn starch and polyion liquid in dimethyl sulfoxide, mixing, heating and stirring;

Step 2): drying the mixture obtained in the step 1) to remove dimethyl sulfoxide to obtain a solid product;

Step 3): heating and melting the solid product obtained in the step 2), and pressing the solid product into a film to obtain the thermoplastic starch film.

4. The method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 3, wherein the concentration of corn starch dissolved in dimethyl sulfoxide in step 1) is 0.08-0.2 g/mL; the concentration of the polyion liquid is 0-0.12g/mL after the polyion liquid is dissolved in dimethyl sulfoxide.

5. The method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 3, wherein the heating temperature in step 1) is 60-110 ℃, the mechanical stirring speed is 150-300r/min, and the heating and stirring time is 50-90 min.

6. The method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 3, wherein the drying temperature in the step 2) is 70-90 ℃ and the drying time is 48-72 h.

7. The method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 3, wherein the solid product is heated and melted by a flat vulcanizing machine in the step 3) and pressurized to form a film, the heating temperature is 150 ℃ and 190 ℃, the heating and melting time is 2-5min, and the applied pressure is 30-70kg/cm²The pressurizing time is 15-45 s.

Technical Field

The invention belongs to the field of starch deep processing, and particularly relates to hydrophobic thermoplastic starch prepared by using polyion liquid as a macromolecular plasticizer and a preparation method thereof.

background

the melting temperature of the starch is higher than the decomposition temperature due to the strong hydrogen bond interaction among molecules in the starch molecule, namely the starch cannot be subjected to thermoplastic processing, so that the application of the starch is greatly limited, and the advantage of biodegradability of the starch cannot be fully exerted, so that the research of the thermoplasticity of the starch by utilizing the plasticizer draws the attention of researchers. Common plasticizers include glycerin, urea, sorbitol and other small molecules, which can effectively form hydrogen bond with starch molecules and lubricate during thermal processing, so that the starch molecules can perform chain motion at a lower temperature and show thermoplasticity macroscopically. However, this plasticizing system has the problem that small molecules are easy to migrate, and after the plasticized thermoplastic starch is stored for a period of time, aggregation and overflow of the plasticizer can be observed by means of an environmental Scanning Electron Microscope (SEM), which can affect the performance stability of the thermoplastic starch material and even cause it to lose its thermoplasticity. Therefore, effectively keeping the properties of the thermoplastic starch material stable is another difficulty which is continuously solved in starch thermoplasticity. In recent years, research shows that Ionic Liquid (IL) has good dissociation effect on a strong hydrogen bond network as a novel solvent, so more and more researchers introduce the ionic liquid into the development of thermoplastic starch. It was found that ionic liquids can impart better hydrophobicity to thermoplastic starch materials and have higher plasticization efficiency than the glycerol system thermoplastic starch materials, but ionic liquids are also a disadvantage of the presence of small molecule plasticizers.

Compared with a micromolecule plasticizer, the macromolecule plasticizer can be stabilized in a plasticized system due to molecular chain entanglement and the like, and the problem caused by plasticizer migration can be solved. However, the newly reported article using polyester-based plasticizers shows that the compatibility between macromolecular plasticizers and starch directly affects the plasticizing effect and the performance of thermoplastic starch materials. Therefore, if a macromolecular plasticizer which can successfully solve the problems of easy migration of small molecules and compatibility with starch can be designed and synthesized, the method has important significance for preparing the thermoplastic starch material with stable performance.

moreover, the polyhydroxy structure of the starch has certain hydrophilicity, so that the requirement on the environment is relatively high in the application process, and certain limitation is realized, so that if the thermoplastic starch material can be further endowed with hydrophobicity, the application problem can be effectively solved, and the application of the starch is expanded.

disclosure of Invention

the technical problem to be solved by the invention is as follows: provides a polyion liquid modified hydrophobic thermoplastic starch and a preparation method thereof.

in order to solve the problems, the invention provides polyion liquid modified hydrophobic thermoplastic starch, which is characterized by comprising corn starch and polyion liquid, wherein the mass ratio of the corn starch to the polyion liquid is (1.0-9.0): 1, wherein the polyionic liquid is Poly [ ECH-MIM ] -DBS.

Preferably, the chemical structural formula of the polyion liquid is as follows:wherein n is 50-5000.

3. The method for preparing polyion liquid modified hydrophobic thermoplastic starch as claimed in claim 1 or 2, characterized by comprising the steps of:

step 1): respectively dissolving corn starch and polyion liquid in dimethyl sulfoxide (DMSO), mixing, heating and stirring;

step 2): drying the mixture obtained in the step 1) to remove dimethyl sulfoxide to obtain a solid product;

Step 3): heating and melting the solid product obtained in the step 2), and pressing the solid product into a film to obtain the thermoplastic starch film.

Preferably, the concentration of the corn starch dissolved in the dimethyl sulfoxide in the step 1) is 0.08-0.2 g/mL; the concentration of the polyion liquid is 0-0.12g/mL after the polyion liquid is dissolved in dimethyl sulfoxide.

preferably, the heating temperature in the step 1) is 60-110 ℃, the mechanical stirring speed is 150-300r/min, and the heating and stirring time is 50-90 min.

Preferably, the drying temperature in the step 2) is 70-90 ℃, and the drying time is 48-72 h.

Preferably, in the step 3), a flat vulcanizing machine is adopted to heat and melt the solid product and pressurize the solid product to form a film, the heating temperature is 150-²the pressurizing time is 15-45 s.

the principle of the invention is that firstly imidazole and epichlorohydrin are used as monomers, and Poly [ ECH-MIM ] -DBS with dodecylbenzene sulfonate ion as anion is synthesized through quaternization reaction and ion exchange reaction; the starch is used as a plasticizer to be mixed with starch, and new hydrogen bonding effect is generated by utilizing anions and cations of the polyionic liquid and hydroxyl groups on starch molecular chains, so that the hydrogen bonding effect between the molecular chains is greatly weakened compared with that of the original starch, the starch molecular chains can slide at a relatively low temperature, and the melting phenomenon is macroscopically expressed, thus obtaining the thermoplastic starch. On the other hand, due to the hydrophobicity of the polyion liquid Poly [ ECH-MIM ] -DBS anion, the thermoplastic starch material can be endowed with hydrophobicity, and the hydrophobic thermoplastic starch in the invention has hydrophobicity after secondary thermoplastic processing, which is different from the common surface hydrophobic modification. The thermoplastic starch material plasticized by the polyionic liquid can be pressed into a sheet by a flat vulcanizing machine, which fully represents the thermoplasticity of the material. And the infrared spectrum, the differential scanning calorimetry image, the thermal weight loss image and the mechanical property test can be used as effective means for analyzing the interaction of the corn starch and the polyion liquid. Particularly, the contact angle of the material is tested by using a full-automatic video microcosmic contact angle measuring instrument, so that the hydrophilicity and hydrophobicity of the material are judged.

the polyionic liquid Poly [ ECH-MIM ] -DBS is designed and synthesized and is used for preparing hydrophobic thermoplastic starch, an imidazole cationic ionic liquid unit is contained on the main chain of the polyionic liquid, and the polyionic liquid contains a hydroxyl structure, anions and cations can form hydrogen bond action with hydroxyl of a starch molecular chain, the effect of effectively avoiding the recombination of the hydrogen bond of starch molecules is achieved, the starch is in an amorphous state, so that the starch obtains thermoplastic processing performance, and hydrophobic dodecyl benzene sulfonate ions on the Poly [ ECH-MIM ] -DBS can bring hydrophobicity to the thermoplastic starch; the preparation method is simple, does not use micromolecular plasticizers, is different from common surface hydrophobic modification, and the obtained thermoplastic starch still has hydrophobicity after secondary thermoplastic processing and good mechanical property, thereby expanding the application field of the starch, optimizing the performance of the thermoplastic starch material and developing the application value of the starch more greatly.

Compared with the prior art, the invention has the beneficial effects that:

The invention utilizes polyion liquid Poly [ ECH-MIM ] -DBS as a macromolecule plasticizer to prepare thermoplastic starch, and modifies the thermoplastic starch to ensure that the starch material has hydrophobicity, and compared with the common surface hydrophobic modified material, the starch material still has hydrophobicity after secondary thermoplastic processing; compared with thermoplastic starch prepared by micromolecular plasticizers, the thermoplastic starch prepared by the method has the advantages of no problem of easy migration of the plasticizer, simple preparation and high mechanical property.

Drawings

FIG. 1 is an infrared spectrum of Poly [ ECH-MIM ] -DBS as the polyion liquid in the invention;

FIG. 2 is a nuclear magnetic hydrogen spectrum of Poly [ ECH-MIM ] -DBS in the present invention;

FIG. 3 is an infrared spectrum of hydrophobic thermoplastic starch prepared in examples 1 to 3 and a comparative example;

FIG. 4 is a differential scanning calorimetry trace of hydrophobic thermoplastic starches obtained in examples 1 to 3 and comparative example;

FIG. 5 is a photograph of a sheet prepared by a press vulcanizer comprising corn starch and the hydrophobic thermoplastic starch obtained in example 1;

FIG. 6 is a contact angle image of hydrophobic thermoplastic starches obtained in examples 1 to 3 and comparative example.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.