Preparation method of polylactic acid anti-fog film

Abstract

The invention discloses a preparation method of a polylactic acid anti-fog film, and belongs to the technical field of plastic film preparation. The anti-fog film is prepared by taking polylactic acid as a matrix, polycaprolactone as a toughening agent, a caprolactone-polyethylene glycol-caprolactone block copolymer as a compatibilizer, a compound of citric acid bonded neodecanoic acid glycidyl ester and decapolyglycerol monolaurate as a hydrophilic agent and dichloromethane as a solvent through solution blending and coating. The polylactic acid film prepared by the invention has better antifogging property and better mechanical property, can be completely biodegraded, is applied to the field of food packaging, and has remarkable economic value and social benefit.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic film preparation, and in particular relates to a method for preparing a polylactic acid anti-fog film. Background Art

[0002] Polylactic acid film has the advantages of high transparency, high mechanical strength, biodegradability, good gas barrier properties, and good biocompatibility. It is gradually replacing traditional petroleum-based polyolefin films for food packaging, electronic product packaging, pharmaceutical packaging, agricultural mulch films and other fields. When polylactic acid film is used in the field of food packaging, the packaged food will evaporate water vapor with changes in temperature and time, and the water vapor condenses on the inner surface of the polylactic acid film to form water mist, which seriously affects the visual effect of the packaged food. At the same time, the rigid molecular structure of polylactic acid causes it to have poor toughness. Therefore, the preparation of polylactic acid films with excellent toughness and anti-fog properties has become the key to promoting its widespread application in the field of food packaging. Summary of the invention

[0003] In view of the problems that the toughness and anti-fogging properties of the current polylactic acid film used in the field of food packaging are poor, the present invention provides a method for preparing a polylactic acid anti-fogging film. The polylactic acid film prepared by the present invention has good anti-fogging properties and excellent mechanical properties, and is completely biodegradable. The use of the polylactic acid film in the field of food packaging has significant economic value and social benefits.

[0004] To achieve the above object, the present invention adopts the following technical solution: A polylactic acid anti-fogging film is prepared by solution blending and coating, with polylactic acid as a matrix, polycaprolactone as a toughening agent, caprolactone-polyethylene glycol-caprolactone block copolymer as a compatibilizer, a compound of citric acid-bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate as a hydrophilic agent, and dichloromethane as a solvent.

[0005] The preparation method of the polylactic acid anti-fogging film specifically comprises the following steps: (1) Under a nitrogen atmosphere, 4-10 g of citric acid was first added to 10-50 g of dioxane, and the mixture was magnetically stirred at 70-90 °C for 10-30 min. Then, 6-8 g of neodecanoic acid glycidyl ester and 0.4-1 g of triphenylphosphine were added, and the mixture was magnetically stirred at 80-100 °C for 3-5 h. After separation, purification, and vacuum drying, citric acid-bonded neodecanoic acid glycidyl ester was obtained. (2) Under a nitrogen atmosphere, 1-3 g of caprolactone and 3-6 g of polyethylene glycol were first magnetically stirred at 80-100 °C for 10-30 min, and then 0.02-0.08 g of tin isooctanoate was added. The mixture was magnetically stirred at 120-140 °C for 6-10 h. After separation, purification and vacuum drying, caprolactone-polyethylene glycol-caprolactone block copolymer was obtained. (3) Adding a mixture of polylactic acid, polycaprolactone, caprolactone-polyethylene glycol-caprolactone block copolymer, citric acid-bonded neodecanoic acid glycidyl ester and polyglycerol monolaurate into dichloromethane in proportion, first stirring the mixture under magnetic stirring at room temperature for 4 to 6 hours, and then ultrasonicating the mixture at room temperature for 5 to 10 minutes to obtain a coating mixture; (4) The coating mixture is coated into a film at a speed of 5 to 10 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0006] Furthermore, the number average molecular weight of the polyethylene glycol in step (2) is 1000, 2000, 4000 or 6000.

[0007] Furthermore, in parts by weight, the amounts of the materials used in step (3) are: 3-5 parts of polylactic acid, 0.5-2 parts of polycaprolactone, 0.05-0.2 parts of caprolactone-polyethylene glycol-caprolactone block copolymer, and 0.2-0.4 parts of a mixture of citric acid-bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate.

[0008] Furthermore, the weight ratio of citric acid bonded neodecanoic acid glycidyl ester to decaglycerol monolaurate in the composite is 0.8:1.2~1.2:0.8.

[0009] The significant advantages of the present invention are: (1) The present invention adopts caprolactone-polyethylene glycol-caprolactone block copolymer as a compatibilizer, which can make polycaprolactone, citric acid-bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate uniformly and stably dispersed in the polylactic acid film. This is because the polyethylene glycol segment has good compatibility with polylactic acid, neodecanoic acid glycidyl ester and decaglycerol monolaurate, and the caprolactone segment has good compatibility with polycaprolactone. At the same time, neodecanoic acid glycidyl ester also has good compatibility with polylactic acid and decaglycerol monolaurate.

[0010] (2) Citric acid has abundant hydroxyl and carboxyl groups and is a highly effective hydrophilic agent with good hydrophilic anti-fogging properties. However, the molecular structure of citric acid is quite different from that of polylactic acid, polycaprolactone and caprolactone-polyethylene glycol-caprolactone block copolymer. Therefore, citric acid is not easy to be uniformly and stably dispersed in the polylactic acid film. The present invention chemically bonds citric acid with neodecanoic acid glycidyl ester by chemical methods, and promotes the uniform and stable dispersion of citric acid in the polylactic acid film through the compatibility between neodecanoic acid glycidyl ester and polylactic acid, polycaprolactone and caprolactone-polyethylene glycol-caprolactone block copolymer.

[0011] (3) Decaglycerol monolaurate has a polyhydroxy molecular structure, is highly hydrophilic, and has excellent hydrophilic anti-fog properties. However, the polyhydroxy molecular structure of decaglycerol monolaurate makes it easy to agglomerate, making it difficult to disperse evenly in the polymer matrix and easy to lose. The present invention uses two hydrophilic agents, decaglycerol monolaurate and citric acid bonded neodecanoic acid glycidyl ester, in a compound. Through the hydrogen bond interaction between the two hydrophilic agent molecules, decaglycerol monolaurate can be effectively promoted to be evenly and stably dispersed in the polylactic acid film.

[0012] (4) The polylactic acid, polycaprolactone, caprolactone-polyethylene glycol-caprolactone block copolymer, citric acid grafted neodecanoic acid glycidyl ester and polyglycerol monolaurate used in the present invention are all non-toxic and biodegradable materials, which are friendly to the environment and have no pollution. Therefore, the polylactic acid anti-fog film prepared by the present invention is an environmentally friendly polymer material, which conforms to the national environmental protection concept and meets the requirements of sustainable development.

[0013] (5) The polycaprolactone uniformly and stably dispersed in the polylactic acid film can give the polylactic acid film excellent toughness, and the citric acid bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate can give the polylactic acid film excellent hydrophilicity. Therefore, the polylactic acid film prepared by the present invention has good hydrophilicity and excellent mechanical properties, with a water contact angle of 9.8~16.9°, an anti-fog failure time of 744~816 min, a tensile strength of 35.8~43.6 MPa, an elongation at break of 231~273%, and is completely biodegradable, suitable for the field of food packaging, and has significant economic value and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the infrared absorption spectrum of citric acid grafted neodecanoic acid glycidyl ester prepared in Example 1.

[0015] Figure 2 This is the infrared absorption spectrum of the caprolactone-polyethylene glycol-caprolactone block copolymer prepared in Example 1. DETAILED DESCRIPTION

[0016] A polylactic acid anti-fog film, the preparation method thereof has the following specific steps: (1) Under nitrogen atmosphere, 4-10 g of citric acid was first added to 10-50 g of dioxane, and magnetically stirred at 70-90 °C for 10-30 min. Then, 6-8 g of neodecanoic acid glycidyl ester and 0.4-1 g of triphenylphosphine were added, and magnetic stirring was continued at 80-100 °C for 3-5 h. After separation, purification, and vacuum drying at 60 °C for 24 h, citric acid-bonded neodecanoic acid glycidyl ester was obtained. (2) Under nitrogen atmosphere, 1-3 g of caprolactone and 3-6 g of polyethylene glycol were magnetically stirred at 80-100 °C for 10-30 min, and then 0.02-0.08 g of tin isooctanoate was added. The mixture was magnetically stirred at 120-140 °C for 6-10 h. After separation, purification and vacuum drying at 60 °C for 24 h, caprolactone-polyethylene glycol-caprolactone block copolymer was obtained. (3) Add 3-5 g of polylactic acid, 0.5-2 g of polycaprolactone, 0.05-0.2 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.2-0.4 g of citric acid-bonded neodecanoic acid glycidyl ester and polyglycerol monolaurate to 20-40 mL of dichloromethane, first stir magnetically at room temperature for 4-6 h, and then ultrasonicate at room temperature for 5-10 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 5 to 10 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0017] Wherein, the number average molecular weight of the polyethylene glycol in step (2) is 1000, 2000, 4000 or 6000.

[0018] The weight ratio of citric acid bonded neodecanoic acid glycidyl ester to decaglycerol monolaurate in the composite material used in step (3) is 0.8:1.2~1.2:0.8.

[0019] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0020] Example 1 (1) Under nitrogen atmosphere, 7 g of citric acid was added to 30 g of dioxane, and the mixture was stirred magnetically at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was stirred magnetically at 90 °C for 4 h. The dioxane was removed by rotary evaporation of the reaction mixture, and then the supernatant was removed by rotary evaporation after being dissolved in dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.3 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1:1) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 8 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0021] Figure 1 The infrared absorption spectrum of citric acid grafted neodecanoic acid glycidyl ester prepared in this example is shown in the figure. It can be seen that in the infrared spectrum of citric acid, it can be clearly observed that the wavelength is 1697 cm -1 and 1747 cm -1 The vibration absorption peak of the carboxyl C=O is about 3500 cm -1 In the infrared absorption spectrum of neodecanoic acid glycidyl ester, it can be clearly observed that the wavelength of the hydroxyl group is 850 cm -1 and 910 cm -1 In the infrared spectrum of citric acid grafted neodecanoic acid glycidyl ester, in addition to the wave number of 850 cm -1 and 910 cm -1 Except for the disappearance of the characteristic absorption peak of the epoxy group at , the characteristic absorption peaks of glycidyl neodecanoate and citric acid can be clearly observed, which indicates that citric acid and glycidyl neodecanoate are successfully chemically bonded.

[0022] Figure 2 FIG. 5 is an infrared absorption spectrum of the caprolactone-polyethylene glycol-caprolactone block copolymer prepared in this example. As shown in the figure, in the infrared absorption spectrum of the caprolactone-polyethylene glycol-caprolactone block copolymer, it can be clearly observed that the wavelength of the caprolactone-polyethylene glycol-caprolactone block copolymer is 3375 cm -1 The hydroxyl stretching vibration absorption peak at 2891 cm -1 and 2946 cm -1 The CH stretching vibration absorption peak at 1725 cm -1 The C=O characteristic absorption peak at 1240 cm -1 The COC stretching vibration absorption peak of the caprolactone chain segment at 1106 cm -1 The CO stretching vibration absorption peak of the polyethylene glycol chain segment was detected, which proved that the caprolactone-polyethylene glycol-caprolactone block copolymer was successfully prepared.

[0023] Example 2 (1) Under nitrogen atmosphere, 7 g of citric acid was first added to 30 g of dioxane, and the mixture was magnetically stirred at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was magnetically stirred at 90 °C for 4 h. The reaction mixture was then subjected to rotary evaporation to remove the dioxane, and then the supernatant was subjected to rotary evaporation to remove the dichloromethane after being dissolved in dichloromethane. Finally, the mixture was vacuum dried at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester. (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.2 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1:1) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 8 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0024] Example 3 (1) Under nitrogen atmosphere, 7 g of citric acid was first added to 30 g of dioxane, and the mixture was magnetically stirred at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was magnetically stirred at 90 °C for 4 h. The reaction mixture was then subjected to rotary evaporation to remove the dioxane, and then the supernatant was subjected to rotary evaporation to remove the dichloromethane after being dissolved in dichloromethane. Finally, the mixture was vacuum dried at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester. (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.4 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1:1) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 8 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0025] Example 4 (1) Under nitrogen atmosphere, 4 g of citric acid was added to 10 g of dioxane and stirred magnetically at 70 °C for 30 min. Then, 6 g of neodecanoic acid glycidyl ester and 0.4 g of triphenylphosphine were added and stirred magnetically at 80 °C for 5 h. The reaction mixture was then subjected to rotary evaporation to remove dioxane and then dissolved in dichloromethane. The supernatant was then subjected to rotary evaporation to remove dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 1 g of caprolactone and 3 g of polyethylene glycol with a number average molecular weight of 1000 were magnetically stirred at 80 °C for 30 min, and then 0.02 g of tin isooctanoate was added. The mixture was magnetically stirred at 120 °C for 10 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 3 g of polylactic acid, 0.5 g of polycaprolactone, 0.05 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.2 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 0.8:1.2) were added to 20 mL of dichloromethane, first magnetically stirred at room temperature for 4 h, and then ultrasonicated at room temperature for 5 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 5 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0026] Example 5 (1) Under nitrogen atmosphere, add 10 g of citric acid to 50 g of dioxane, stir magnetically at 90 °C for 10 min, then add 8 g of neodecanoic acid glycidyl ester and 1 g of triphenylphosphine, stir magnetically at 100 °C for 3 h, then remove dioxane by rotary evaporation, dissolve in dichloromethane, and remove the supernatant by rotary evaporation. AfterThe mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 3 g of caprolactone and 6 g of polyethylene glycol with a number average molecular weight of 4000 were magnetically stirred at 100 °C for 10 min, and then 0.08 g of tin isooctanoate was added. The mixture was magnetically stirred at 140 °C for 6 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) Add 5 g of polylactic acid, 2 g of polycaprolactone, 0.2 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.4 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1.2:0.8) into 40 mL of dichloromethane, first magnetically stir at room temperature for 6 h, then ultrasonicate at room temperature for 10 min to prepare a coating mixture; (4) The coating mixture is coated into a film at a speed of 10 mm / s, and after natural air drying, the polylactic acid anti-fogging film is obtained.

[0027] Comparative Example 1 (1) Add 4 g of polylactic acid and 1 g of polycaprolactone into 30 mL of dichloromethane, stir magnetically at room temperature for 5 h, and then ultrasonicate at room temperature for 8 min to prepare a coating mixture; (2) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0028] Comparative Example 2 (1) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (2) Add 4 g of polylactic acid, 1 g of polycaprolactone and 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer into 30 mL of dichloromethane, stir magnetically at room temperature for 5 h, and then ultrasonicate at room temperature for 8 min to prepare a coating mixture; (3) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0029] Comparative Example 3 (1) Under nitrogen atmosphere, 7 g of citric acid was added to 30 g of dioxane, and the mixture was stirred magnetically at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was stirred magnetically at 90 °C for 4 h. The dioxane was removed by rotary evaporation of the reaction mixture, and then the supernatant was removed by rotary evaporation after being dissolved in dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) 4 g of polylactic acid, 1 g of polycaprolactone, 0.3 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1:1) were added to 30 mL of dichloromethane, firstly magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (3) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0030] Comparative Example 4 (1) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (2) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, and 0.3 g of polyglycerol monolaurate were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (3) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0031] Comparative Example 5 (1) Under nitrogen atmosphere, 7 g of citric acid was added to 30 g of dioxane, and the mixture was stirred magnetically at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was stirred magnetically at 90 °C for 4 h. The dioxane was removed by rotary evaporation of the reaction mixture, and then the supernatant was removed by rotary evaporation after being dissolved in dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) Add 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, and 0.3 g of citric acid grafted neodecanoic acid glycidyl ester into 30 mL of dichloromethane, first stir magnetically at room temperature for 5 h, and then ultrasonicate at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0032] Comparative Example 6 (1) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (2) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.3 g of a mixture of glycidyl neodecanoate and polyglycerol monolaurate (the weight ratio of glycidyl neodecanoate to polyglycerol monolaurate is 1:1) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to obtain a coating mixture; (3) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0033] Comparative Example 7 (1) Under nitrogen atmosphere, 7 g of citric acid was added to 30 g of dioxane, and the mixture was stirred magnetically at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was stirred magnetically at 90 °C for 4 h. The dioxane was removed by rotary evaporation of the reaction mixture, and then the supernatant was removed by rotary evaporation after being dissolved in dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.3 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 0.5:1.5) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0034] Comparative Example 8 (1) Under nitrogen atmosphere, 7 g of citric acid was added to 30 g of dioxane, and the mixture was stirred magnetically at 80 °C for 20 min. Then, 7 g of neodecanoic acid glycidyl ester and 0.7 g of triphenylphosphine were added, and the mixture was stirred magnetically at 90 °C for 4 h. The dioxane was removed by rotary evaporation of the reaction mixture, and then the supernatant was removed by rotary evaporation after being dissolved in dichloromethane. After The mixture was dried under vacuum at 60 °C for 24 h to obtain citric acid grafted neodecanoic acid glycidyl ester; (2) Under nitrogen atmosphere, 2 g of caprolactone and 4.5 g of polyethylene glycol with a number average molecular weight of 2000 were magnetically stirred at 90 °C for 20 min, and then 0.05 g of tin isooctanoate was added. The mixture was magnetically stirred at 130 °C for 8 h. The reactants were dissolved in dichloromethane, precipitated with excess ether, washed with methanol, and dried at 60 °C in vacuum for 24 h to obtain caprolactone-polyethylene glycol-caprolactone block copolymer. (3) 4 g of polylactic acid, 1 g of polycaprolactone, 0.1 g of caprolactone-polyethylene glycol-caprolactone block copolymer, 0.3 g of a mixture of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate (the weight ratio of citric acid grafted neodecanoic acid glycidyl ester to decaglycerol monolaurate is 1.5:0.5) were added to 30 mL of dichloromethane, first magnetically stirred at room temperature for 5 h, and then ultrasonicated at room temperature for 8 min to prepare a coating mixture; (4) The coating mixture is applied into a film at a speed of 8 mm / s, and the finished product is obtained after natural air drying.

[0035] The thickness of the finished products obtained from the embodiments and comparative examples was tested with a spiral micrometer, and the static water contact angle test was performed according to GB / T30693-2014, and the tensile strength and elongation at break were tested according to GB / T 1040.3-2006. At the same time, the long-term anti-fog performance of the film was tested. The specific operation was to first pour 200 mL of deionized water into a 250 mL flat beaker, and then fix the film to the mouth of the beaker with a rubber band, and finally place the beaker in a 40°C constant temperature water tank, start timing, and when the water droplet area of ​​the film at the mouth of the beaker exceeds 50%, it is judged that the anti-fog property of the film has failed, and the time displayed by the timer is used to characterize the long-term anti-fog property of the film. The test results are shown in Table 1.

[0036] Table 1 Performance test results

[0037] It can be seen from the test results of the embodiments and comparative examples that the polylactic acid anti-fogging film prepared in the embodiments has good anti-fogging properties and excellent mechanical properties, among which the polylactic acid anti-fogging film prepared in Example 1 has better performance in all aspects. In contrast, if the caprolactone-polyethylene glycol-caprolactone block copolymer is used alone (Comparative Example 2) or the composite of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate is used alone (Comparative Example 3), or only one of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate is used (Comparative Examples 4 and 5) and the composite of neodecanoic acid glycidyl ester and decaglycerol monolaurate without citric acid grafting is used (Comparative Example 6), or the weight ratio of citric acid grafted neodecanoic acid glycidyl ester and decaglycerol monolaurate in the composite is greatly different (Comparative Examples 7 and 8), a polylactic acid anti-fogging film with good anti-fogging properties and excellent mechanical properties cannot be obtained.

[0038] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a polylactic acid anti-fog film, Features: The anti-fog film is prepared by using polylactic acid as a matrix, polycaprolactone as a toughening agent, caprolactone-polyethylene glycol-caprolactone block copolymer as a compatibilizer, a compound of citric acid-bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate as a hydrophilic agent, and dichloromethane as a solvent through solution blending and coating.

2. The method for preparing the polylactic acid antifogging film according to claim 1, Features: The specific steps include: (1) Under a nitrogen atmosphere, 4-10 g of citric acid was first added to 10-50 g of dioxane, and the mixture was magnetically stirred at 70-90 °C for 10-30 min. Then, 6-8 g of neodecanoic acid glycidyl ester and 0.4-1 g of triphenylphosphine were added, and the mixture was magnetically stirred at 80-100 °C for 3-5 h. After separation, purification, and vacuum drying, citric acid-bonded neodecanoic acid glycidyl ester was obtained. (2) Under a nitrogen atmosphere, 1-3 g of caprolactone and 3-6 g of polyethylene glycol were first magnetically stirred at 80-100 °C for 10-30 min, and then 0.02-0.08 g of tin isooctanoate was added, and the mixture was magnetically stirred at 120-140 °C for 6-10 h. After separation, purification, and vacuum drying, caprolactone-polyethylene glycol-caprolactone block copolymer was obtained; (3) Adding a mixture of polylactic acid, polycaprolactone, caprolactone-polyethylene glycol-caprolactone block copolymer, citric acid-bonded neodecanoic acid glycidyl ester and polyglycerol monolaurate into dichloromethane in proportion, first stirring the mixture under magnetic stirring at room temperature for 4 to 6 hours, and then ultrasonicating the mixture at room temperature for 5 to 10 minutes to obtain a coating mixture; (4) The coating mixture is coated to form a film, and after natural air drying, the polylactic acid anti-fogging film is obtained.

3. The method for preparing the polylactic acid antifogging film according to claim 2, Features: The number average molecular weight of the polyethylene glycol in step (2) is 1000, 2000, 4000 or 6000.

4. The method for preparing the polylactic acid antifogging film according to claim 2, Features: In parts by weight, the amounts of the materials used in step (3) are: 3-5 parts of polylactic acid, 0.5-2 parts of polycaprolactone, 0.05-0.2 parts of caprolactone-polyethylene glycol-caprolactone block copolymer, and 0.2-0.4 parts of a mixture of citric acid-bonded neodecanoic acid glycidyl ester and decaglycerol monolaurate; Wherein, the weight ratio of citric acid bonded neodecanoic acid glycidyl ester to decaglycerol monolaurate in the composite is 0.8:1.2~1.2:0.

8.

5. A polylactic acid antifogging film prepared by any method as claimed in claims 1 to 4.

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