Preparation method and application of maleic anhydride and triethanolamine molten polymer

Abstract

The invention relates to a preparation method and application of a maleic anhydride and triethanolamine molten polymer, and belongs to the technical field of preparation of bio-based degradable composite films. The method comprises the following steps: reacting maleic anhydride with triethanolamine through a melt polymerization method to obtain a polyester compound, adding the polyester compound into a starch / chitosan blended emulsion, and carrying out a solution casting method to obtain the modified starch / chitosan composite material. When the addition amount of the maleic anhydride triethanolamine molten polymer is 0.75 part, the tensile strength reaches the strength peak value of 10.97 MPa, the elongation at break retention rate reaches 107% while the strength is optimized, and at the moment, the composite film has relatively excellent mechanical properties, and can be applied to the field of medical instruments, such as medical instruments, medical instruments, medical instruments and the like. Meanwhile, the transparency index of the composite film under the ratio is also improved by 13.02%, and the optical performance is synchronously improved; the composite film is expected to be applied to the fields of food packaging, agricultural mulching films and the like.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a maleic anhydride and triethanolamine molten polymer, belonging to the technical field of preparation of bio-based degradable composite films. Background Art

[0002] Petroleum-based plastic films are widely used in food packaging due to their excellent packaging properties. However, this leads to excessive consumption of petroleum resources and environmental pollution caused by waste. Driven by the need for sustainable development, the research and development of biodegradable plastics has become an inevitable trend. Starch, as a natural biopolymer, combines the advantages of abundant natural resources, low cost, strong renewability, and excellent biodegradability, making it a research hotspot in the field of bioactive packaging materials. Furthermore, chitosan, due to its unique antimicrobial and antioxidant properties, shows significant potential in the development of biodegradable active food packaging materials. Research has shown that films prepared by combining starch and chitosan not only retain the biobased and biodegradable properties of both components, but also achieve complementary and optimized performance through synergistic interaction. This composite system provides an innovative solution for the food packaging industry that combines environmental and functional properties, further promoting the green transformation of the packaging industry. However, it should be noted that, as with most polymer-polymer interactions, the composite of starch and chitosan suffers from poor compactness, resulting in insufficient mechanical and barrier properties.

[0003] In order to solve the above problems, the patent of patent number CN105061818B discloses a method for preparing a degradable composite film, which adopts an efficient composite modifier, with starch and chitosan as raw materials, and prepares the starch / chitosan composite film through a blow molding process. The three main components contained in the composite modifier are component one, choline chloride, ammonium chloride, one or more, component two, ferric nitrate, ferric chloride, and component three, organic small molecule glycerol, ethylene glycol, ethanolamine, and formamide. One or more. The disadvantage of this method is that its preparation process is relatively cumbersome, which increases the difficulty of cost control. In addition, although this method has achieved remarkable results in improving elongation at break (toughness index), achieving a substantial increase of 271%, it is regrettable that it has failed to achieve its goal in terms of tensile strength, but instead has experienced a 45.7% decline. The patent of patent number CN108395582B specifically discloses a cassava starch-polyvinyl alcohol-chitosan composite film and its preparation method. The core of this patent lies in the clever introduction of nano-SiO2 particles as a modifier to enhance the mechanical properties of the film. In order to further optimize the uniform dispersion of nano-SiO2 in the composite material, a highly efficient dispersant was specially selected to achieve the ideal nano-scale dispersion effect, thereby improving the overall performance of the film. Specifically, although this method has achieved significant results in enhancing tensile strength, achieving a 104% increase, its elongation at break has unfortunately decreased, falling to 63.3% of the original value.

[0004] The present invention is dedicated to solving a difficult problem in the current technical field of starch / chitosan composite films: that is, while improving the strength of the film, it is often accompanied by a decrease in the elongation at break, which in turn causes the material to become more brittle.

[0005] Therefore, the present invention first provides a method for preparing a maleic anhydride triethanolamine molten polymer.

[0006] The present invention also provides application of maleic anhydride triethanolamine molten polymer as a reinforcement and toughening agent for starch / chitosan composite film.

[0007] Specifically, the triethanolamine melt polymer reinforced toughening agent starch / chitosan composite film of the present invention is composed of the following components by weight:

[0008] Starch 18

[0009] Chitosan 2

[0010] Maleic anhydride triethanolamine molten compound 0.20~1.00

[0011] The specific method adopted by the present invention is:

[0012] 1) Preparation of maleic anhydride triethanolamine melt polymer

[0013] The preparation process adopts melt polymerization: 8 to 12 parts of maleic anhydride and 13 to 18 parts of triethanolamine are mixed in a container, first mixed and stirred at room temperature for 30 minutes, then the temperature is raised to 50 to 65°C to allow the maleic anhydride and triethanolamine to undergo an esterification reaction, while a condensing reflux device is opened and maintained for 30 minutes. Finally, the system is heated to 120°C, at which point the esterification product begins to polymerize. The reaction time is 0.8 to 1.5 hours, thereby obtaining a maleic anhydride triethanolamine melt polymer.

[0014] 2) Preparation of starch / chitosan composite films with maleic anhydride triethanolamine melt polymer toughening agent

[0015] The method adopts a solution casting method: 18 parts of starch are prepared into a starch emulsion, 2 parts of chitosan are dissolved in a 1% acetic acid solution to prepare a chitosan emulsion, and the starch emulsion and the chitosan emulsion are mixed in equal proportions; 0.25 to 1.00 parts of a maleic anhydride triethanolamine molten polymer are added, and the mixture is uniformly mixed again. The film liquid is vacuum-evacuated and then cast onto a carrier. The film is dried in a vacuum oven at 45 to 55° C. to form a film. After the film is solidified, the film is peeled off from the carrier to obtain a starch-maleic anhydride triethanolamine molten polymer-chitosan composite film.

[0016] The advantages of the present invention are:

[0017] 1) Starch and chitosan are widely available, low in cost, and have good market application prospects;

[0018] 2) Maleic anhydride triethanolamine melt polymer significantly improves the tensile strength of starch / chitosan composite films while maintaining a stable and high elongation at break;

[0019] 3) The maleic anhydride triethanolamine molten polymer improves the optical properties of the starch / chitosan composite film; BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Preparation Mechanism of Maleic Anhydride Triethanolamine Melt Polymer

[0021] Figure 2 NMR spectra of maleic anhydride, triethanolamine and molten polymer

[0022] As attached Figure 2The chemical shifts of the carbon atoms labeled in the maleic anhydride-triethanolamine molten polymer are shown in Figure 2. The chemical shifts at positions 52.5 and 54.9 in the composite correspond to the C1 and C2 positions of triethanolamine, while the chemical shifts at positions 134.3 and 166 in the composite correspond to the C1 and C2 positions of maleic anhydride. These carbon chemical shifts represent a structure containing maleic anhydride and triethanolamine. The chemical shift at position 58.6 in the composite indicates an esterification reaction between maleic anhydride and triethanolamine. The attribution analysis of the characteristic peaks in the carbon spectrum indicates that the target composite is a polyester compound formed by the esterification reaction between maleic anhydride and triethanolamine. DETAILED DESCRIPTION

[0023] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0024] In the following examples and comparative examples, the prepared films were cut into standard strips of 40×10×0.6 mm and measured using an E44.304 electronic universal testing machine manufactured by MTS Industrial Systems (China) Co., Ltd. at a tensile rate of 50 mm / min.

[0025] Comparative Example 1; (blank)

[0026] Take 18g of starch, dissolve it in 250mL of deionized water, react in a 90℃ water bath for 15min, add 3g of glycerol and continue to react for 15min to obtain a starch emulsion; dissolve 2g of chitosan in 250mL of 1.0% acetic acid solution and stir for 30min to obtain a chitosan emulsion, and mix the above two emulsions in equal proportions for 15min; after the solution is cooled to room temperature, the membrane liquid is vacuum-evacuated and then cast onto a carrier, placed in a vacuum oven, and dried at 45℃ for 24h for drying. After the membrane is solidified, the membrane is peeled off from the carrier to obtain a starch / chitosan composite film; finally, the composite film is placed in a humidistat with a relative humidity of 70% and stored for later use.

[0027] Example 1:

[0028] 1) Preparation of maleic anhydride triethanolamine melt polymer

[0029] Weigh 10g of maleic anhydride and 15g of triethanolamine, add them to a three-necked flask with a serpentine condenser, a stirrer and a thermometer, and then place the flask in a constant temperature oil bath. First, mix at room temperature for 30 minutes, then raise the temperature to 50-65°C, turn on the condensation reflux and maintain for 30 minutes, and finally heat to 120°C to start the polymerization reaction of the esterification product, and the polymerization reaction lasts for 1 hour. At the same time, since the polymerization of maleic anhydride and triethanolamine is a ring-opening polymerization, in order to avoid water in the system, the water molecules in the system are removed by vacuum method. Use a vacuum pump to maintain the pressure in the flask at 0.2MPa. Finally, a light yellow viscous liquid synthesis product is obtained. That is, maleic anhydride triethanolamine molten polymer;

[0030] 2) Maleic anhydride triethanolamine melt polymer reinforced toughened starch / chitosan composite film

[0031] 18 g of starch was dissolved in 240 mL of deionized water, reacted in a 90° C. water bath for 15 min, 3 g of glycerol was added, and the reaction was continued for 15 min to obtain a starch emulsion. 2 g of chitosan was dissolved in 250 mL of 1.0% acetic acid solution and stirred for 30 min to obtain a chitosan emulsion. The two emulsions were mixed in equal proportions for 15 min, 0.25 g of maleic anhydride triethanolamine molten polymer was dissolved in 10 mL of deionized water, and added to the starch / chitosan mixed emulsion and mixed evenly. After the solution was cooled to room temperature, the film liquid was vacuum-evacuated and then cast onto a carrier. The film was placed in a vacuum oven and dried at 45° C. for 24 h for drying. After the film was solidified, the film was peeled off from the carrier to obtain a starch-maleic anhydride triethanolamine molten polymer-chitosan composite film. Finally, the composite film was placed in a humidistat with a relative humidity of 70% for storage.

[0032] Example 2:

[0033] 1) Preparation of maleic anhydride triethanolamine melt polymer

[0034] The method for preparing the maleic anhydride triethanolamine melt polymer composite is similar to the method for preparing the maleic anhydride triethanolamine melt polymer in Example 1;

[0035] 2) Maleic anhydride triethanolamine melt polymer reinforced toughened starch / chitosan composite film

[0036] 18 g of starch was dissolved in 240 mL of deionized water, reacted in a 90° C. water bath for 15 min, 3 g of glycerol was added, and the reaction was continued for 15 min to obtain a starch emulsion. 2 g of chitosan was dissolved in 250 mL of 1.0% acetic acid solution and stirred for 30 min to obtain a chitosan emulsion. The two emulsions were mixed in equal proportions for 15 min, 0.50 g of maleic anhydride triethanolamine molten polymer was dissolved in 10 mL of deionized water, and added to the starch / chitosan mixed emulsion and uniformly mixed. After the solution was cooled to room temperature, the film liquid was vacuum-evacuated and cast onto a carrier. The film was placed in a vacuum oven and dried at 45° C. for 24 h for drying. After the film was solidified, the film was peeled off from the carrier to obtain a starch-maleic anhydride triethanolamine molten polymer-chitosan composite film. Finally, the composite film was placed in a humidistat with a relative humidity of 70% for storage.

[0037] Example 3:

[0038] 1) Preparation of maleic anhydride triethanolamine melt polymer

[0039] The method for preparing the maleic anhydride triethanolamine molten polymer is similar to the method for preparing the maleic anhydride triethanolamine molten polymer in Example 1;

[0040] 2) Maleic anhydride triethanolamine melt polymer reinforced toughened starch / chitosan composite film

[0041] 18 g of starch was dissolved in 240 mL of deionized water, reacted in a 90° C. water bath for 15 min, 3 g of glycerol was added, and the reaction was continued for 15 min to obtain a starch emulsion. 2 g of chitosan was dissolved in 250 mL of 1.0% acetic acid solution and stirred for 30 min to obtain a chitosan emulsion. The two emulsions were mixed in equal proportions for 15 min, 0.75 g of maleic anhydride triethanolamine molten polymer was dissolved in 10 mL of deionized water, and added to the starch / chitosan mixed emulsion and mixed evenly. After the solution was cooled to room temperature, the film liquid was vacuum-evacuated and then cast onto a carrier. The film was placed in a vacuum oven and dried at 45° C. for 24 h for drying. After the film was solidified, the film was peeled off from the carrier to obtain a starch-maleic anhydride triethanolamine molten polymer-chitosan composite film. Finally, the composite film was placed in a humidistat with a relative humidity of 70% for storage.

[0042] Example 4:

[0043] 1) Preparation of maleic anhydride triethanolamine melt polymer

[0044] The method for preparing the maleic anhydride triethanolamine molten polymer is similar to the method for preparing the maleic anhydride triethanolamine molten polymer in Example 1;

[0045] 2) Maleic anhydride triethanolamine melt polymer reinforced toughened starch / chitosan composite film

[0046] 18 g of starch was dissolved in 240 mL of deionized water, reacted in a 90° C. water bath for 15 min, 6 g of glycerol was added, and the reaction was continued for 15 min to obtain a starch emulsion. 2 g of chitosan was dissolved in 250 mL of 1.0% acetic acid solution and stirred for 30 min to obtain a chitosan emulsion. The two emulsions were mixed in equal proportions for 15 min, 1.00 g of maleic anhydride triethanolamine molten polymer was dissolved in 10 mL of deionized water, and added to the starch / chitosan mixed emulsion and mixed evenly. After the solution was cooled to room temperature, the film liquid was vacuum-evacuated and then cast onto a carrier. The film was placed in a vacuum oven and dried at 40° C. for 24 h for drying. After the film was solidified, the film was peeled off from the carrier to obtain a starch-maleic anhydride triethanolamine molten polymer-chitosan composite film. Finally, the composite film was placed in a humidistat with a relative humidity of 70% for storage.

[0047] The test data results of the above comparative examples and embodiments are shown in Table 1.

[0048] The test data for strength (tensile strength) and toughness (elongation at break) for the comparative examples and examples in Table 1 show that when the addition amount of maleic anhydride triethanolamine molten polymer is in the range of 0.25-1.00 parts, the strength of the composite film is significantly enhanced, resulting in a significant increase in tensile strength of 166%-296% (p<0.05) for the modified system compared to the pure matrix comparative example. Notably, the elongation at break of all examples did not suffer a corresponding loss due to the increased strength. This synergistic strength-toughness enhancement effect is most prominent in Example 3, where Example 3 (with an addition amount of 3.75%) reaches a peak strength of 10.97 MPa. While optimizing strength, this system also maintains an elongation at break of 107%, demonstrating excellent overall performance. Furthermore, a systematic evaluation of the optical properties of the composite films revealed a nonlinear relationship between the addition amount of maleic anhydride triethanolamine molten polymer and the opacity of the composite system. As the additive content increases from 0.25 to 1.00 parts, the opacity of the film shows a trend of first decreasing and then increasing. When the addition amount is 0.75 parts, an inflection point is formed, and the opacity index (2.94mm -1 )Compared to the control example (3.38mm -1 ) was significantly reduced by 86.98% (p<0.01), reaching the minimum value in the embodiment group.

[0049] A comprehensive comparison of the test data of the examples and comparative examples in Table 1 above shows that the maleic anhydride triethanolamine melt polymer can achieve a breakthrough improvement in the mechanical properties of the composite film within the range of 0.25-1.00 parts. The formulation design of Example 3 successfully establishes a dual optimization system of mechanical properties and optical properties by precisely controlling the dosage of additives. This synergistic optimization mechanism of dual properties provides key technical parameters for the development of new biodegradable packaging materials with both high transparency and UV resistance, and is suitable for packaging with stringent requirements for optical properties.

[0050] Table 1

[0051]

Claims

1. A preparation method and application of a molten polymer of maleic anhydride and triethanolamine, characterized in that: The preparation method and application of maleic anhydride triethanolamine molten polymer are obtained according to the following steps: 8-12 parts of maleic anhydride and 13-18 parts of triethanolamine are mixed in a container, first mixed and stirred at room temperature for 30 minutes, then the temperature is raised to 50°C to 65°C to allow the maleic anhydride and triethanolamine to undergo an esterification reaction, while a condensing reflux device is turned on and maintained for 30 minutes, and finally the system is heated to 120°C, at which point the esterification product begins to polymerize, and the reaction time is 0.8-1.5 hours to obtain a maleic anhydride triethanolamine molten polymer; 18 parts of starch are prepared into a starch emulsion, and 2 parts of chitosan are dissolved in a 1% by mass acetic acid solution to prepare a chitosan emulsion; the starch and chitosan emulsions are mixed in equal proportions for 15 minutes; then 0.25 to 1.00 parts of a molten polymer of maleic anhydride triethanolamine are added and uniformly mixed again for 30 minutes; the mixed emulsion is vacuum-evacuated and then cast onto a carrier; and then dried in a vacuum oven at 45°C to 55°C to form a film; When the addition amount of maleic anhydride triethanolamine molten polymer is 0.75 parts, the starch / chitosan composite film has the best modification effect on improving mechanical properties and optical properties.

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