PLA-PGA compatibilizer, preparation method of efficient gas barrier PLA / PGA alloy membrane material and PLA / PGA alloy

Abstract

The invention discloses a preparation method of a PLA-PGA compatibilizer and an efficient gas barrier PLA / PGA alloy membrane material, and a PLA / PGA alloy. The preparation method of the PLA-PGA compatibilizer comprises the following steps: adding an allyl alcohol derivative and diisocyanate into an organic solvent, and reacting at room temperature to obtain an intermediate product; drying PGA in an air dry oven, adding the dried PGA and the intermediate product in the step (1) into a stirrer, uniformly mixing, and further adding the mixture into a double-screw extruder for extrusion granulation to obtain modified PGA; and drying PLA and the modified PGA in a drying oven, adding an initiator, uniformly mixing, extruding, cooling and pelletizing to obtain the PLA-PGA compatibilizer. The compatibilizer has a good compatibilization effect on the PLA / PGA alloy and high compatibilization efficiency, a PLA / PGA alloy film prepared from the compatibilizer can efficiently resist gas, and the strength, modulus, toughness and other mechanical properties of the PLA / PGA alloy are improved.

Description

Technical Field

[0001] The invention relates to the field of preparation of PLA / PGA alloys, and in particular to a PLA-PGA compatibilizer, a preparation method of a high-efficiency gas barrier PLA / PGA alloy film material, and a PLA / PGA alloy. Background Art

[0002] With the continuous development of society, the consumption of traditional petroleum-based materials is increasing, and the white garbage generated by their large-scale use has caused serious pollution to the environment. People have begun to look for biodegradable materials to replace traditional petroleum-based materials. Polylactic acid (PLA) has become one of the most widely used biodegradable materials due to its high strength, high modulus and biodegradability. It is widely used in packaging, medical devices and other fields. Especially in the field of food packaging, due to its short service life, PLA has been widely used and consumed in large quantities. However, PLA has low barrier properties and cannot well block O2, H2O, etc. in the air, making the quality of the prepared food packaging materials low.

[0003] Polyglycolic acid (PGA) is an aliphatic polyester with the simplest chemical structure. It is rapidly biodegradable and 100% compostable. PGA also has excellent barrier properties and is very competitive in green packaging. The gas permeability coefficient of PGA is about 1000 times lower than that of PLA, and the water vapor permeability coefficient is about 38 times lower than that of PLA. Therefore, PGA can make up for the shortcomings of PLA in terms of barrier properties and improve the barrier properties of the film. Therefore, PGA can be compounded with PLA to obtain a degradable high-barrier composite film.

[0004] However, there is a compatibility problem between PLA and PGA. In order to obtain high-performance PLA / PGA composites, the compatibility of PLA and PGA needs to be further improved. The main ways to increase compatibility are inorganic particle expansion and organic compatibilizer expansion. Due to the large size of inorganic particles, they are prone to agglomeration, which limits their application in packaging film materials. Organic compatibilizers have good compatibility with polymer matrices, high expansion efficiency and good effects. They are currently a commonly used method for expanding polymer alloys or composites. However, due to the different interfacial tensions between organic compatibilizers and the two-phase polymers, it is difficult to effectively distribute them at the interface between the two phases, resulting in low expansion efficiency. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a PLA-PGA compatibilizer, which contains PLA and PGA molecular chains and has good compatibilization effect and high compatibilization efficiency on PLA / PGA alloy.

[0006] Another object of the present invention is to provide a method for preparing a highly efficient gas barrier PLA / PGA alloy film material. The prepared PLA / PGA alloy film material can not only efficiently block gases such as O2 and H2O in the air, and avoid oxidation and deterioration of food during storage, but also PLA and PGA have good compatibility at the molecular scale, thereby improving the mechanical properties of the PLA / PGA alloy in terms of strength, modulus and toughness.

[0007] Another object of the present invention is to provide a PLA / PGA alloy for preparing a high-efficiency gas barrier PLA / PGA alloy film material.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a method for preparing a PLA-PGA compatibilizer, comprising the following steps:

[0010] (1) adding an allyl alcohol derivative and a diisocyanate into an organic solvent and reacting them at room temperature to obtain an intermediate product;

[0011] (2) drying the PGA in a forced air drying oven, adding the PGA and the intermediate product in step (1) in a molar ratio of 1:1 to 4:1 into a mixer and mixing them evenly, adding the mixture into a twin-screw extruder for extrusion and granulation to obtain modified PGA;

[0012] (3) After PLA and modified PGA are dried in an oven, PLA, modified PGA and an initiator are uniformly mixed and then placed in a twin-screw extruder for melt blending. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained;

[0013] Wherein, the ratio of PLA to modified PGA is 7:3-3:7.

[0014] Preferably, the molar ratio of the allyl alcohol derivative to the diisocyanate is 1:1-1:5.

[0015] Preferably, the allyl alcohol derivative is at least one of allyl alcohol, methacrylate glycidyl ether, methyl allyl alcohol, and allyl alcohol glycidyl ether; and the diisocyanate is at least one of hexamethylene diisocyanate, toluene diisocyanate, and xylylene diisocyanate.

[0016] Preferably, the reaction time is 10 min-60 min.

[0017] Preferably, in the twin-screw extruder of step (2), the maximum screw temperature is 225-250°C, the main screw speed is 60-120rpm, and the feeding screw speed is 20-60rpm; in the twin-screw extruder of step (3).

[0018] Preferably, the initiator is at least one of dicumyl peroxide, di-tert-butyl cumene peroxide and di-tert-butyl peroxide.

[0019] The present invention also provides a method for preparing a high-efficiency gas barrier PLA / PGA alloy film material, comprising the following steps:

[0020] PLA / PGA alloy particles are melted by a single screw extruder and cast into film. After the film is cut, it is biaxially stretched to 100%-400% of its original size and finally annealed at 120℃-180℃ for 1h-3h.

[0021] The PLA / PGA alloy particles are prepared by the following method:

[0022] After PLA, PGA and the PLA-PGA compatibilizer are dried in an oven, PLA, PGA and the PLA-PGA compatibilizer are uniformly mixed and placed in a twin-screw extruder for melt blending, and PLA / PGA alloy particles are obtained after extrusion through a die head, cooling and pelletizing.

[0023] Preferably, the PLA / PGA alloy particles contain, by weight: 60 to 70 parts of PLA; 20 to 30 parts of PGA; and 5 to 15 parts of the PLA-PGA compatibilizer.

[0024] Preferably, in the step of placing the mixture in a twin-screw extruder for melt blending, the maximum temperature of the twin-screw extruder is 225° C. to 250° C., the main screw speed is 60 to 120 rpm, and the feeding screw speed is 20 to 60 rpm.

[0025] The present invention also provides a PLA / PGA alloy, including PLA and PGA, and a LA-PGA compatibilizer prepared by the preparation method of the PLA-PGA compatibilizer.

[0026] Preferably, in the step of drying in an oven, the drying temperature of the oven is 50° C. to 90° C., the drying time is 4 h to 12 h, the optimal drying temperature is 80° C., and the drying time is 6 h.

[0027] Preferably, the added amount of the PLA-PGA compatibilizer is 5%-15% of the total mass of PLA and PGA; the initiator in the PLA-PGA compatibilizer accounts for 0.8-1.2% of the total mass of the PLA / PGA alloy.

[0028] The principle of the present invention is:

[0029] The PLA-PGA compatibilizer of the present invention connects allyl alcohol derivatives and diisocyanate to both ends of a PGA molecular chain to obtain a modified PGA, and after the isocyanate group reacts with the allyl alcohol, it reacts with the terminal hydroxyl group of PGA to obtain a modified PGA with a terminal C=C double bond. The modified PGA and PLA are further melt-blended, and under the action of an initiator, high temperature and shearing, the free radicals on the PLA molecular chain react chemically with the C=C double bonds at both ends of the modified PGA to obtain the PLA-PGA compatibilizer.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The PLA-PGA compatibilizer of the present invention contains PLA and PGA molecular chains, and has a good compatibilization effect and high compatibilization efficiency on the PLA / PGA alloy.

[0032] (2) The method for preparing the high-efficiency gas barrier PLA / PGA alloy film material of the present invention increases the PGA grain size by adding the PLA-PGA compatibilizer of the present invention and performing stretching and annealing treatment, thereby further improving the gas barrier performance of the PLA / PGA alloy film.

[0033] (3) The PLA / PGA alloy of the present invention is a fully biodegradable alloy, which has the advantages of energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the reaction process for preparing modified PGA according to an embodiment of the present invention.

[0035] Figure 2 It is a schematic diagram of the reaction process of preparing PLA-PGA compatibilizer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0037] Example 1

[0038] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0039] (1) Hexamethylene diisocyanate (HDI) (20 g) and allyl alcohol (6.9 g) (molar ratio 1:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0040] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 2:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA. The reaction process for preparing modified PGA is as follows: Figure 1 shown.

[0041] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are mixed uniformly in a mass ratio of 69.5 / 29.5 / 1, and then melt blended in a twin-screw extruder at a maximum temperature of 230°C and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained. The reaction process is as follows: Figure 2 shown.

[0042] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0043] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 65 / 25 / 10, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0044] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0045] The prepared PLA / PGA alloy particles were cast into a film through a single-screw extruder, the film was cut into square samples of 90×90 mm, and further biaxially stretched to 400% of the original length and width. Finally, the film was annealed at 150°C for 1 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0046] Example 2

[0047] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0048] (1) Hexamethylene diisocyanate (HDI) (40 g) and allyl alcohol (6.9 g) (molar ratio 2:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0049] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 2:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0050] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69.5 / 29.5 / 1, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0051] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0052] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 65 / 25 / 10, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0053] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0054] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 400% of the original length and width. Finally, the film was annealed at 150°C for 1 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0055] Example 3

[0056] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0057] (1) Hexamethylene diisocyanate (HDI) (40 g) and allyl alcohol (6.9 g) (molar ratio 2:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0058] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 2:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0059] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69 / 29 / 2, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0060] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0061] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 67 / 27 / 6, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0062] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0063] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into 90×90 mm square samples and further biaxially stretched to 200% of the original length and width. Finally, the film was annealed at 150°C for 3 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0064] Example 4

[0065] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0066] (1) Hexamethylene diisocyanate (HDI) (40 g) and allyl alcohol (6.9 g) (molar ratio 2:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0067] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 3:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0068] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69 / 29 / 2, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0069] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0070] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 66 / 26 / 8, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0071] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0072] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 200% of the original length and width. Finally, the film was annealed at 150°C for 1 hour to obtain a PLA / PGA alloy film with high gas barrier properties.

[0073] Example 5

[0074] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0075] (1) Hexamethylene diisocyanate (HDI) (60 g) and allyl alcohol (6.9 g) (molar ratio 3:1) were added to an alkali oven and reacted at room temperature for 40 min using DMF as solvent to obtain an intermediate product A.

[0076] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 2:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0077] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69 / 29 / 2, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0078] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0079] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 65 / 25 / 10, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0080] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0081] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 200% of the original length and width. Finally, the film was annealed at 170°C for 1 hour to obtain a PLA / PGA alloy film with high gas barrier properties.

[0082] Example 6

[0083] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0084] (1) Hexamethylene diisocyanate (HDI) (60 g) and allyl alcohol (6.9 g) (molar ratio 3:1) were added to an alkali oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0085] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 4:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0086] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 68.5 / 28.5 / 3, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0087] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0088] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 65 / 25 / 10, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0089] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0090] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 400% of the original length and width. Finally, the film was annealed at 150°C for 1 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0091] Example 7

[0092] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0093] (1) Hexamethylene diisocyanate (HDI) (20 g) and allyl alcohol (6.9 g) (molar ratio 1:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0094] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 4:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0095] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69.5 / 29.5 / 1, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0096] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0097] After PLA, PGA, and PLA-PGA compatibilizer were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizer were uniformly mixed in a mass ratio of 65 / 25 / 10, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling, and pelletizing, a PLA / PGA alloy was obtained.

[0098] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0099] The PLA / PGA alloy was cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 400% of the original length and width. Finally, the film was annealed at 150°C for 1 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0100] Example 8

[0101] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0102] (1) Hexamethylene diisocyanate (HDI) (40 g) and allyl alcohol (6.9 g) (molar ratio 2:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0103] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 4:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0104] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69.5 / 29.5 / 1, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0105] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0106] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 67.5 / 27.5 / 5, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0107] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0108] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into 90×90 mm square samples and further biaxially stretched to 400% of the original length and width. Finally, the film was annealed at 150°C for 2 h to obtain a PLA / PGA alloy film with high gas barrier properties.

[0109] Example 9

[0110] The PLA-PGA compatibilizer of this embodiment is prepared as follows:

[0111] (1) Hexamethylene diisocyanate (HDI) (40 g) and allyl alcohol (6.9 g) (molar ratio 2:1) were added to an alkali-free oven and reacted at room temperature for 20 min using DMF as solvent to obtain an intermediate product A.

[0112] (2) After the reaction is completed, the intermediate product A obtained in step (1) is mixed with PGA particles at a ratio of 3:1 (mol), and added to a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm for extrusion and granulation to obtain modified PGA.

[0113] (3) After PLA and modified PGA are dried, PLA, modified PGA and DCP are uniformly mixed in a mass ratio of 69.5 / 29.5 / 1, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained.

[0114] The PLA / PGA alloy particles of this embodiment are prepared as follows:

[0115] After PLA, PGA, and PLA-PGA compatibilizers were dried at 60° C. in an oven, PLA, PGA, and PLA-PGA compatibilizers were uniformly mixed in a mass ratio of 67.5 / 27.5 / 5, and then melt-blended in a twin-screw extruder at a maximum temperature of 230° C. and a screw speed of 80 rpm. PLA / PGA alloy particles were obtained after extrusion through a die, cooling, and pelletizing.

[0116] The preparation of the high-efficiency gas barrier PLA / PGA alloy film material of this embodiment is as follows:

[0117] The PLA / PGA alloy particles were cast into a film through a single-screw extruder, and the film was cut into square samples of 90×90 mm and further biaxially stretched to 100% of the original length and width. Finally, the film was annealed at 150°C for 1 hour to obtain a PLA / PGA alloy film with high gas barrier properties.

[0118] Comparative Example 1

[0119] The difference from the embodiment is that the preparation formula of the PLA / PGA composite material is, calculated by mass fraction, 80wt% of PLA material and 20wt% of PGA.

[0120] Comparative Example 2

[0121] The difference from the embodiment is that HDI is not added to the system, and allyl alcohol, PGA, PLA and DCP are directly blended in one step, wherein the mass ratio is PLA:PGA:allyl alcohol:DCP=69:29:1.5:0.5.

[0122] Example performance test results

[0123] Performance test: refer to the national standards "GB / T 1040 Determination of tensile properties" and "GB 1038-2000 Test method for gas permeability of plastic films and sheets".

[0124] Tensile property test: The tensile properties were measured at room temperature by using a universal tensile testing instrument (Instron 5967, USA) at a crosshead speed of 10 mm / min, and the result of each sample was expressed as the average of at least five independent specimens.

[0125] Gas barrier performance test: Water vapor transmission rate (WVP) and oxygen transmission rate (OP) were used to evaluate the barrier performance of the film. WVP was tested using a W3 / 060 water vapor permeation permeameter at 90% relative humidity, 1 atm and 38°C. According to GB1038-2000, the OP of the film was tested using a C130 differential pressure gas permeameter at 0% relative humidity, 1 atm and 23°C, and the average of five tests was taken.

[0126] The test results of the embodiments and comparative examples are shown in Table 1 and Table 2.

[0127] Table 1. Results of mechanical properties of PLA / PGA alloy films

[0128]

[0129] Table 2. PLA / PGA alloy film gas barrier properties test results

[0130]

[0131]

[0132] It can be seen from the above examples that by adding the compatibilizer provided by the present invention, the PLA / PGA alloy film prepared has excellent strength and modulus as well as low oxygen and water vapor permeability, the tensile strength can reach up to 215.2MPa, the Young's modulus reaches 3227.7MPa, and the water vapor permeability is as low as 0.54×10 -14 g cm -2 ·s -1 ·pa -1 , and 0.79×10 - 15 cm 3 ·cm·cm -2 ·s -1 ·pa -1 Therefore, the PLA-PGA compatibilizer and the preparation method of the PLA / PGA alloy film prepared by the present invention enable the PLA / PGA alloy film to successfully achieve excellent mechanical properties and gas barrier properties.

[0133] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a PLA-PGA compatibilizer, characterized in that: The following steps are involved: (1) adding an allyl alcohol derivative and a diisocyanate into an organic solvent and reacting them at room temperature to obtain an intermediate product; (2) drying the PGA in a forced air drying oven, adding the PGA and the intermediate product in step (1) in a molar ratio of 1:1 to 4:1 into a mixer and mixing them evenly, adding the mixture into a twin-screw extruder for extrusion and granulation to obtain modified PGA; (3) After PLA and modified PGA are dried in an oven, PLA, modified PGA and an initiator are uniformly mixed and then placed in a twin-screw extruder for melt blending. After extrusion through a die, cooling and pelletizing, a PLA-PGA compatibilizer is obtained; Wherein, the ratio of PLA to modified PGA is 7:3-3:

7.

2. The method for preparing a PLA-PGA compatibilizer according to claim 1, wherein The molar ratio of the allyl alcohol derivative to the diisocyanate is 1:1-1:

5.

3. The preparation method of the PLA-PGA compatibilizer according to claim 1, characterized in that: The allyl alcohol derivative is at least one of allyl alcohol, methacrylate glycidyl ether, methyl allyl alcohol, and allyl alcohol glycidyl ether; the diisocyanate is at least one of hexamethylene diisocyanate, toluene diisocyanate, and xylylene diisocyanate.

4. The method for preparing the PLA-PGA compatibilizer according to claim 1, characterized in that: The reaction time is 10 min-60 min.

5. The method for preparing the PLA-PGA compatibilizer according to claim 1, characterized in that: In the twin-screw extruder of step (2), the maximum screw temperature is 225-250°C, the main screw speed is 60-120rpm, and the feeding screw speed is 20-60rpm; in the twin-screw extruder of step (3).

6. The method for preparing the PLA-PGA compatibilizer according to claim 1, characterized in that: The initiator is at least one of dicumyl peroxide, di-tert-butyl cumene peroxide and di-tert-butyl peroxide.

7. A method for preparing a highly efficient gas barrier PLA / PGA alloy film material, characterized in that: The following steps are involved: PLA / PGA alloy particles are melted by a single screw extruder and cast into film. After the film is cut, it is biaxially stretched to 100%-400% of its original size and finally annealed at 120℃-180℃ for 1h-3h. The PLA / PGA alloy particles are prepared by the following method: After PLA, PGA and the PLA-PGA compatibilizer are dried in an oven, PLA, PGA and the PLA-PGA compatibilizer are uniformly mixed and placed in a twin-screw extruder for melt blending, and PLA / PGA alloy particles are obtained after extrusion through a die head, cooling and pelletizing.

8. The method for preparing a high-efficiency gas barrier PLA / PGA alloy film material according to claim 7, characterized in that: In parts by weight, the PLA / PGA alloy particles contain: 60 to 70 parts of PLA; 20 to 30 parts of PGA; and 5 to 15 parts of the PLA-PGA compatibilizer.

9. The method for preparing a high-efficiency gas barrier PLA / PGA alloy film material according to claim 7, characterized in that: In the step of placing the mixture in a twin-screw extruder for melt blending, the maximum temperature of the twin-screw extruder is 225° C. to 250° C., the main screw speed is 60 to 120 rpm, and the feeding screw speed is 20 to 60 rpm.

10. A PLA / PGA alloy, characterized in that: The invention relates to a LA-PGA compatibilizer comprising PLA, PGA and the LA-PGA compatibilizer prepared by the preparation method of the PLA-PGA compatibilizer according to any one of claims 1 to 6.

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