CN103146008A - Preparation method of alkali lignin-starch film - Google Patents

Abstract

The invention discloses a preparation method of an alkali lignin-starch film, which relates to a preparation method of an alkali lignin-starch film. The present invention aims to solve the problem of phase separation in the blended film caused by low molecular weight in the existing method in the film processing process. The method of the present invention is as follows: 1. Prepare starch gelatinization liquid; 2. Prepare film-making liquid; 3. Cool the film-making solution to room temperature, then vacuum degassing, then pour the film-making solution on a stainless steel plate and spread it flat, then dry it, then let it stand at room temperature, and peel off the film to obtain an alkali lignin-starch film , which completes the preparation method of the alkali lignin-starch film. The invention is applied in the fields of agriculture and gardening, fruit and vegetable packaging, and daily chemicals.

Description

A kind of preparation method of alkali lignin-starch film

technical field

The invention relates to a preparation method of alkali lignin-starch film.

Background technique

Since the 1980s, researchers have focused on the development of modified starch films and blend films of starch and biodegradable polymers. Chiellini et al. conducted research on the application of some biodegradable polyester materials such as polyhydroxyalkyl esters, polylactic acid, and polycaprolactam in starch-based materials. The results of the research showed that these materials are not only biodegradable and biocompatible capacitive, and its mechanical properties are also very good. However, the use cost of these polymers is relatively high, which is not conducive to the industrialization of materials. In order to make raw materials cheap and easy to obtain, Funke et al. began to search for suitable natural polymer compounds from agricultural products, such as cellulose, lignin, pectin, chitin and protein, etc., and developed a fully biodegradable starch-based film. Among these natural polymer compounds, lignin is the main by-product of the paper industry and the emerging biomass fuel ethanol industry, and its resource utilization and high-value utilization have been the focus of researchers for a long time.

The first chapter "Starch-lignin films" written by Baumberger in "Chemical Modification, Properties, and Usage of Lignin" published in 2002 (Thomas Q.Hu, Kluwer Academic/plenum Publishers, New York, 2002, 1-20.) ", reviewed the preparation methods, thermodynamic properties, interaction mechanism of starch and lignin, and potential application prospects of starch-lignin blends. In the film processing process of glycerol, there is a phenomenon of phase separation in the blend liquid caused by low molecular weight.

Contents of the invention

The invention aims to solve the problem of phase separation in the blended film caused by low molecular weight in the film processing process of the existing method, and provides a preparation method of the alkali lignin-starch film.

A kind of preparation method of alkali lignin-starch film of the present invention is carried out through the following steps: 1. Mix cornstarch with water to prepare a cornstarch aqueous solution with a mass percentage of 1% to 10%, and then heat up while stirring to 95°C, and keep it for 15-25 minutes to obtain starch gelatinization solution; 2. Add hydroxymethylated alkali lignin, with a mass percentage of 50% glutaraldehyde and glycerin, to the gelatinization solution obtained in step 1, and cool down to 20-90°C, react for 1-5h, and obtain the film-making solution; 3. Cool the film-making solution obtained in step 2 to room temperature, then vacuum defoam, spread and cast, and then place it in a constant temperature drying oven at 70°C , kept for 1 to 2 hours, then taken out, left to stand at room temperature for 8 to 12 hours, and the film was peeled off to obtain an alkali lignin-starch film, that is, the preparation method of the alkali lignin-starch film was completed; wherein the corn starch in step 1 and step 2 The mass ratio of hydroxymethylated alkali lignin is 1: (0.2～1), and the mass volume ratio of cornstarch in step 1 and the mass percentage content of 50% glutaraldehyde in step 2 is 1g: (0.1～1 ) mL, the mass volume ratio of cornstarch in step 1 to glycerin in step 2 is 1g: (0.5～2) mL.

The present invention utilizes the cross-linking reaction to improve the compatibility of starch and alkali lignin in the composite material, and introduces the hydroxymethyl functional group into the alkali lignin molecule, so that the water absorption rate of the composite membrane material exceeds that of starch and alkali lignin. Compared with the blended film, the alkali lignin-starch film of the present invention has a uniform and soft texture. After soaking in water for 24 hours, the shape of the film material does not change significantly, and the material is still very uniform without blister formation. ,;Using scanning electron microscopy to observe the surface and cross-sectional microscopic morphology of the membrane material, it was found that the components in the membrane material had good compatibility and no obvious phase separation occurred.

Therefore, it can be used as a moisture-retaining film material in fields such as agriculture and horticulture, fruit and vegetable packaging, and daily chemicals.

Description of drawings

Fig. 1 is the SEM photograph of the alkali lignin-starch film surface that test 1 prepares;

Fig. 2 is the SEM photo of the alkali lignin-starch film section prepared in experiment 1.

Detailed ways

Specific embodiment one: the preparation method of a kind of alkali lignin-starch film of this embodiment is carried out through the following steps: one, cornstarch is mixed with water to prepare the cornstarch aqueous solution that the mass percentage content is 1%～10% , and then heat up to 95°C while stirring, and keep it for 15-25min to obtain starch gelatinization liquid; 2. Add hydroxymethylated alkali lignin to the gelatinization liquid obtained in step 1, the mass percentage is 50% amylose Dialdehyde and glycerin, lower the temperature to 20-90°C, react for 1-5h, and obtain the film-forming liquid; 3. Cool the film-forming liquid obtained in step 2 to room temperature, then vacuum degassing, flat casting, and then place at 70 ℃ in a constant temperature drying oven, keep it for 1-2 hours, then take it out, let it stand at room temperature for 8-12 hours, and peel off the film to obtain an alkali lignin-starch film, which is to complete the preparation method of the alkali lignin-starch film; wherein step 1 The mass ratio of corn starch in step 2 to hydroxymethylated alkali lignin is 1: (0.2～1), and the mass volume ratio of corn starch in step 1 to 50% glutaraldehyde in step 2 is 1g: (0.1-1) mL, the mass-volume ratio of cornstarch in step 1 to glycerin in step 2 is 1 g: (0.5-2) mL.

In this embodiment, the cross-linking reaction is used to improve the compatibility of starch and alkali lignin in the composite material, and by introducing hydroxymethyl functional groups into the alkali lignin molecules, the water absorption rate of the composite membrane material exceeds that of starch and alkali lignin. Compared with the blended film, the alkali lignin-starch film of the present embodiment has a uniform and soft texture. After soaking in water for 24 hours, the shape of the film material does not change significantly, and the material is still very uniform. Formation of blisters; using a scanning electron microscope to observe the microscopic morphology of the surface and cross-section of the membrane material, it is found that the components in the membrane material have good compatibility and no obvious phase separation occurs, so it can be used as a moisture-retaining membrane material in agriculture Horticulture, fruit and vegetable packaging, daily chemicals and other fields.

Embodiment 2: This embodiment differs from Embodiment 1 in that in step 1, cornstarch and water are mixed to prepare an aqueous solution of cornstarch with a mass percentage of 3% to 7%. Other steps and parameters are the same as those in the first embodiment.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that in Step 1, cornstarch and water are mixed to prepare an aqueous solution of cornstarch with a mass percentage of 5%. Other steps and parameters are the same as those in Embodiment 1 or 2.

Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is that in step 1, the temperature is raised to 95° C. within 40 minutes. Other steps and parameters are the same as those in the first to third specific embodiments.

Embodiment 5: This embodiment is different from Embodiment 1 to Embodiment 4 in that the temperature is lowered to 50° C. in step 2. Other steps and parameters are the same as one of the specific embodiments 1 to 4.

Embodiment 6: The difference between this embodiment and one of Embodiments 1 to 5 is that the reaction is 2h in step 2. Other steps and parameters are the same as one of the specific embodiments 1 to 5.

Embodiment 7: This embodiment is different from Embodiment 1 to Embodiment 6 in that step 3 is kept for 1.5h. Other steps and parameters are the same as one of the specific embodiments 1 to 6.

Embodiment 8: The difference between this embodiment and one of Embodiments 1 to 7 is that the mass ratio of cornstarch in step 1 to hydroxymethylated alkali lignin in step 2 is 1:0.7. Other steps and parameters are the same as one of the specific embodiments 1 to 7.

Embodiment 9: The difference between this embodiment and Embodiment 1 to Embodiment 8 is that the mass volume ratio of corn starch in step 1 to 50% glutaraldehyde in step 2 is 1 g: 0.1 mL. Other steps and parameters are the same as one of the specific embodiments 1 to 8.

Embodiment 10: This embodiment differs from Embodiment 1 to Embodiment 9 in that the mass-volume ratio of cornstarch in step 1 to glycerin in step 2 is 1 g: 0.8 mL. Other steps and parameters are the same as one of the specific embodiments 1 to 9.

Prove the beneficial effect of the present invention by following test:

Test 1, the preparation method of a kind of alkali lignin-starch film of this test is carried out by following steps: one, cornstarch is mixed with water preparation mass percentage composition to be the cornstarch aqueous solution of 5%, then heat up while stirring To 95 ℃, and keep 20min, obtain starch gelatinization liquid; 2, add hydroxymethylated alkali lignin, mass percentage content is 50% glutaraldehyde and glycerol to the gelatinization liquid obtained in step 1, cool to 50 ℃, reacted for 2 hours, and obtained the film-making solution; 3. Cool the film-making solution obtained in step 2 to room temperature, and then vacuum degassing, then pour the film-making solution on a stainless steel plate and cast it flatly, and then put the film-making solution with The liquid stainless steel plate is placed in a constant temperature drying oven at 70°C, kept for 1.5h, then taken out, left to stand at room temperature for 10h, and the film is peeled off to obtain an alkali lignin-starch film, that is, the preparation method of the alkali lignin-starch film is completed. wherein the mass ratio of cornstarch in step one to hydroxymethylated alkali lignin in step two is 1: 0.7, and the mass volume ratio of cornstarch in step one to the mass percentage of 50% glutaraldehyde in step two is 1g: 0.1mL, the mass volume ratio of cornstarch in step 1 to glycerin in step 2 is 1g: 0.8mL.

The water absorption rate of the alkali lignin-starch film prepared in this test is 146.3%. The alkali lignin-starch film prepared in this test is tested by TG and DSC. The test results show that the alkali lignin-starch film has stable thermal properties below 90 °C , using a scanning electron microscope to observe the surface and cross-sectional microscopic morphology of the alkali lignin-starch film, the results are shown in Figure 1 and Figure 2. From Figure 1 and Figure 2, it can be seen that in the alkali lignin-starch film prepared in this test The compatibility between the components is good, and no obvious phase separation occurs. The alkali lignin-starch film was tested for mechanical properties according to GB13022-91. The elongation at break of the alkali lignin-starch film prepared in this test was 62.54%. The elongation at break of the existing lignin-starch blend film is 21.52%, and the water absorption rate is 35.6%. Compared with the existing lignin-starch blend film, the elongation at break of the alkali lignin-starch film prepared in this test Therefore, the alkali lignin-starch film prepared in this experiment has good flexibility, good toughness and high water absorption rate, and can be used as a moisture-retaining film material in agriculture and horticulture, fruit and vegetable packaging, daily chemicals and other fields.

Claims (10)

1. a preparation method of alkali lignin-starch film is characterized in that the preparation method of alkali lignin-starch film is carried out by the following steps: one, cornstarch is mixed with water and the preparation mass percentage is 1%～ 10% cornstarch aqueous solution, then heat up to 95°C while stirring, and keep it for 15-25min to obtain starch gelatinization liquid; 2. Add hydroxymethylated alkali lignin, mass 100% The component content is 50% glutaraldehyde and glycerin, lower the temperature to 20-90 ° C, and react for 1-5 hours to obtain the film-forming liquid; 3. Cool the film-forming liquid obtained in step 2 to room temperature, then vacuum degassing, flat flow Then put it in a constant temperature drying oven at 70°C for 1-2 hours, then take it out, let it stand at room temperature for 8-12 hours, and peel off the film to obtain an alkali lignin-starch film, that is, complete the alkali lignin-starch film. Preparation method; wherein the mass ratio of corn starch in step 1 to hydroxymethylated alkali lignin in step 2 is 1: (0.2-1), and the mass percentage of corn starch in step 1 and step 2 is 50% pentadiene The mass volume ratio of aldehyde is 1g:(0.1～1)mL, and the mass volume ratio of cornstarch in step 1 to glycerin in step 2 is 1g:(0.5～2)mL. 2. The preparation method of a kind of alkali lignin-starch film according to claim 1, characterized in that in step 1, cornstarch is mixed with water to prepare an aqueous cornstarch solution with a mass percentage of 3% to 7%. 3. the preparation method of a kind of alkali lignin-starch film according to claim 1, it is characterized in that in step 1, cornstarch and water are mixed to prepare the cornstarch aqueous solution that mass percentage composition is 5%. 4. The method for preparing an alkali lignin-starch film according to claim 1, characterized in that step 1 heats up to 95° C. within 40 minutes. 5. The preparation method of a kind of alkali lignin-starch film according to claim 1, characterized in that in step 2, the temperature is lowered to 50°C. 6. The preparation method of a kind of alkali lignin-starch film according to claim 1, characterized in that in step 2, react for 2h. 7. the preparation method of a kind of alkali lignin-starch film according to claim 1 is characterized in that keeping 1.5h in step 3. 8. The preparation method of a kind of alkali lignin-starch film according to claim 1, characterized in that the mass ratio of corn starch in step 1 to hydroxymethylated alkali lignin in step 2 is 1:0.7. 9. the preparation method of a kind of alkali lignin-starch film according to claim 1 is characterized in that the mass percentage composition of cornstarch and step 2 in the step 2 is that the mass volume ratio of 50% glutaraldehyde is 1g: 0.1mL. 10. The preparation method of a kind of alkali lignin-starch film according to claim 1, characterized in that the mass volume ratio of cornstarch in step 1 to glycerin in step 2 is 1g: 0.8mL.

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