Preparation Method of Polylactic Acid / Montmorillonite / Nanocrystalline Cellulose Whisker Composite Material

Abstract

The present invention discloses a preparation method of a polylactic acid / montmorillonite / nanocellulose whisker composite material, which relates to the technical field of polylactic acid composite materials. In the present invention, polylactic acid is first chemically modified and then melt-blended to prepare a polylactic acid / montmorillonite / nanocellulose whisker composite material. Using montmorillonite and nanocellulose whiskers as the reinforcing phases of polylactic acid, the prepared composite material not only retains the excellent biodegradable properties of polylactic acid, but also improves the processing performance and mechanical properties of polylactic acid, simplifies the raw material formula of the composite material, reduces the preparation workload, and lowers the raw material cost.

Description

Technical Field:

[0001] The present invention relates to the technical field of polylactic acid composite materials, and particularly relates to a preparation method of a polylactic acid / montmorillonite / nano cellulose whisker composite material. Background Art:

[0002] Polylactic acid is a biodegradable material obtained by lactic acid condensation or lactide ring-opening polymerization. After use, it can be completely degraded by microorganisms in nature, and finally generate carbon dioxide and water without polluting the environment, which is very beneficial to environmental protection and is a recognized environmentally friendly material. Polylactic acid has good thermal stability, a processing temperature of 170 - 230 °C, good solvent resistance, and can be processed in various ways, such as extrusion, spinning, biaxial stretching, injection blow molding. Products made of polylactic acid have good biodegradability, biocompatibility, gloss, transparency, feel, and heat resistance. However, due to the presence of polar ester groups in the polylactic acid molecule, polylactic acid is brittle and has poor toughness, which severely limits the popularization and application of polylactic acid.

[0003] Currently, the modification methods of polylactic acid mainly include blending modification and chemical modification. The blending modification method is to add a flexible polymer or a small molecule plasticizer to polylactic acid, such as polybutylene adipate terephthalate, polybutylene succinate, polyethylene glycol, epoxidized soybean oil, tributyl citrate, etc. Although this method can improve the performance of polylactic acid to a certain extent, the added components have poor compatibility with polylactic acid, resulting in unstable performance of polylactic acid products. The chemical modification method is to carry out a chemical reaction between other functional monomers or groups and polylactic acid and combine them in a covalent bond manner, and the binding force is relatively strong and stable. Summary of the Invention:

[0004] The technical problem to be solved by the present invention is to provide a preparation method of a polylactic acid / montmorillonite / nano cellulose whisker composite material, which modifies polylactic acid by combining chemical modification and blending modification, optimizes the processing performance and mechanical properties of polylactic acid under the condition of retaining the biodegradability of polylactic acid, and prepares a polylactic acid / montmorillonite / nano cellulose whisker composite material that can be applied to textile processing.

[0005] One of the purposes of the present invention is to provide a preparation method of a polylactic acid / montmorillonite / nano cellulose whisker composite material, including the following preparation steps:

[0006] (1) Dissolve polylactic acid in 1,4 - dioxane, then add N - allyl - N,N - bis(trimethylsilyl)amine and an initiator, heat under reflux for reaction. After the reaction is completed, distill off the solvent and unreacted N - allyl - N,N - bis(trimethylsilyl)amine under reduced pressure, wash the concentrate with water, and dry it under vacuum to obtain graft - modified polylactic acid;

[0007] (2) fully mixing the grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and a compatibilizer to obtain a mixture;

[0008] (3) adding the above mixture into a twin-screw extruder, extruding and granulating after melting and plasticizing to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0009] The boiling point of 1,4-dioxane is 101°C and it is miscible with water. The trace amount of 1,4-dioxane remaining after recovery by vacuum distillation can be removed by water washing. The boiling point of N-allyl-N,N-bis(trimethylsilyl)amine is relatively low, and the unreacted N-allyl-N,N-bis(trimethylsilyl)amine can be recovered by vacuum distillation.

[0010] Preferably, the amount of N-allyl-N,N-bis(trimethylsilyl)amine added is 5-20% of the mass of the polylactic acid.

[0011] The present invention adopts N-allyl-N,N-bis(trimethylsilyl)amine to chemically graft modify polylactic acid, retaining the original terminal carboxyl groups and terminal hydroxyl groups of the polylactic acid, because the presence of the terminal carboxyl groups can catalyze the hydrolysis of the polylactic acid, accelerate the degradation rate of the polylactic acid, and thus ensure the degradability of the polylactic acid.

[0012] Preferably, the initiator is selected from one or more of benzoyl peroxide, diisopropylbenzene peroxide and di-tert-butyl peroxide.

[0013] Preferably, the added amount of the initiator is 0.1-1% of the mass of the polylactic acid.

[0014] Preferably, the added amount of the montmorillonite is 1-5% of the mass of the graft-modified polylactic acid.

[0015] Preferably, the added amount of the nanocellulose whiskers is 1-5% of the mass of the grafted modified polylactic acid.

[0016] Preferably, the amount of the compatibilizer added is 1-10% of the mass of the graft-modified polylactic acid.

[0017] Preferably, the compatibilizer is a silane coupling agent.

[0018] The present invention uses montmorillonite and nanocellulose whiskers as reinforcing phases to improve the processing performance and mechanical properties of polylactic acid, but due to the poor compatibility between montmorillonite and nanocellulose whiskers and polylactic acid, they are prone to agglomeration, so a compatibilizer needs to be added to promote the uniform dispersion of montmorillonite and nanocellulose whiskers in the polylactic acid matrix. Under anhydrous conditions, the siloxane bond of the silane coupling agent reacts with the surface hydroxyl groups of montmorillonite and nanocellulose whiskers to achieve modification.

[0019] The feeding section temperature of the twin-screw extruder is 150 - 160 °C, the compression section temperature is 190 - 200 °C, the metering section temperature is 200 - 210 °C, the head temperature is 200 - 210 °C, and the screw speed is 50 - 100 r / min.

[0020] The second object of the present invention is to provide a polylactic acid / montmorillonite / nanocellulose whisker composite material prepared according to the foregoing preparation method.

[0021] The third object of the present invention is to provide the application of the polylactic acid / montmorillonite / nanocellulose whisker composite material in textile processing. After the polylactic acid / montmorillonite / nanocellulose whisker composite material prepared by the present invention is made into composite fibers through a spinning process, it can be used for textile processing.

[0022] The beneficial effects of the present invention are as follows: The present invention first chemically modifies polylactic acid and then blends and modifies it to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material. Using montmorillonite and nanocellulose whiskers as the reinforcing phases of polylactic acid, the prepared composite material not only retains the excellent biodegradable performance of polylactic acid, but also improves the processing performance and mechanical properties of polylactic acid, simplifies the raw material formula of the composite material, reduces the preparation workload, and lowers the raw material cost. Specific embodiments:

[0023] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0024] In the following examples and comparative examples, the polylactic acid is Haizheng Biopharm REVODE701; the montmorillonite is nano-montmorillonite from Zhejiang Fenghong New Materials Co., Ltd., with a particle size of 15 μm; the nanocellulose whiskers are from Zhongke Leiming (Beijing) Technology Co., Ltd., with a diameter of 10 - 50 nm.

[0025] Example 1

[0026] Preparation of polylactic acid / montmorillonite / nanocellulose whisker composite material:

[0027] (1) Dissolve polylactic acid in 1,4-dioxane, then add N-allyl-N,N-bis(trimethylsilyl)amine and di-tert-butyl peroxide, heat under reflux until the viscosity of the system no longer changes, after the reaction is completed, recover the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine by vacuum distillation, wash the concentrate with water, and dry it under vacuum to obtain graft-modified polylactic acid. Among them, the addition amount of N-allyl-N,N-bis(trimethylsilyl)amine is 10% of the mass of polylactic acid, and the addition amount of di-tert-butyl peroxide is 0.2% of the mass of polylactic acid.

[0028] (2) The grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and silane coupling agent KH570 prepared above are fully mixed to obtain a mixture, wherein the amount of montmorillonite added is 3% of the mass of the grafted modified polylactic acid, the amount of nanocellulose whiskers added is 5% of the mass of the grafted modified polylactic acid, and the amount of silane coupling agent KH570 added is 5% of the mass of the grafted modified polylactic acid.

[0029] (3) Add the prepared mixture into a twin-screw extruder, melt and plasticize it, and then extrude it into granules. The feeding section temperature of the twin-screw extruder is 150-160°C, the compression section temperature is 190-200°C, the metering section temperature is 200-210°C, the head temperature is 200-210°C, and the screw speed is 100r / min to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0030] Example 2

[0031] Preparation of polylactic acid / montmorillonite / nanocellulose whisker composites:

[0032] (1) Dissolve polylactic acid in 1,4-dioxane, then add N-allyl-N,N-bis(trimethylsilyl)amine and diisopropylbenzene peroxide, heat and reflux to react until the viscosity of the system no longer changes, and after the reaction is completed, distill under reduced pressure to recover the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine, wash the concentrate with water, and vacuum dry to obtain graft-modified polylactic acid. The amount of N-allyl-N,N-bis(trimethylsilyl)amine added is 15% of the mass of the polylactic acid, and the amount of diisopropylbenzene peroxide added is 0.5% of the mass of the polylactic acid.

[0033] (2) The grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and silane coupling agent KH570 prepared above are fully mixed to obtain a mixture, wherein the amount of montmorillonite added is 5% of the mass of the grafted modified polylactic acid, the amount of nanocellulose whiskers added is 3% of the mass of the grafted modified polylactic acid, and the amount of silane coupling agent KH570 added is 5% of the mass of the grafted modified polylactic acid.

[0034] (3) Add the prepared mixture into a twin-screw extruder, melt and plasticize it, and then extrude it into granules. The feeding section temperature of the twin-screw extruder is 150-160°C, the compression section temperature is 190-200°C, the metering section temperature is 200-210°C, the head temperature is 200-210°C, and the screw speed is 100r / min to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0035] Example 3

[0036] Preparation of polylactic acid / montmorillonite / nanocellulose whisker composites:

[0037] (1) Dissolve polylactic acid in 1,4-dioxane, then add N-allyl-N,N-bis(trimethylsilyl)amine and benzoyl peroxide, heat and reflux to react until the viscosity of the system no longer changes, and after the reaction is completed, distill under reduced pressure to recover the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine, wash the concentrate with water, and vacuum dry to obtain graft-modified polylactic acid. The amount of N-allyl-N,N-bis(trimethylsilyl)amine added is 5% of the mass of the polylactic acid, and the amount of benzoyl peroxide added is 0.2% of the mass of the polylactic acid.

[0038] (2) The grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and silane coupling agent KH550 prepared above are fully mixed to obtain a mixture, wherein the amount of montmorillonite added is 5% of the mass of the grafted modified polylactic acid, the amount of nanocellulose whiskers added is 5% of the mass of the grafted modified polylactic acid, and the amount of silane coupling agent KH550 added is 8% of the mass of the grafted modified polylactic acid.

[0039] (3) Add the prepared mixture into a twin-screw extruder, melt and plasticize it, and then extrude it into granules. The feeding section temperature of the twin-screw extruder is 150-160°C, the compression section temperature is 190-200°C, the metering section temperature is 200-210°C, the head temperature is 200-210°C, and the screw speed is 100r / min to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0040] Example 4

[0041] Preparation of polylactic acid / montmorillonite / nanocellulose whisker composites:

[0042] (1) Dissolve polylactic acid in 1,4-dioxane, then add N-allyl-N,N-bis(trimethylsilyl)amine and diisopropylbenzene peroxide, heat and reflux to react until the viscosity of the system no longer changes, and after the reaction is completed, distill under reduced pressure to recover the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine, wash the concentrate with water, and vacuum dry to obtain graft-modified polylactic acid. The amount of N-allyl-N,N-bis(trimethylsilyl)amine added is 20% of the mass of the polylactic acid, and the amount of diisopropylbenzene peroxide added is 0.5% of the mass of the polylactic acid.

[0043] (2) The grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and silane coupling agent KH560 prepared above are fully mixed to obtain a mixture, wherein the amount of montmorillonite added is 4% of the mass of the grafted modified polylactic acid, the amount of nanocellulose whiskers added is 3% of the mass of the grafted modified polylactic acid, and the amount of silane coupling agent KH560 added is 5% of the mass of the grafted modified polylactic acid.

[0044] (3) Add the prepared mixture into a twin-screw extruder, melt and plasticize it, and then extrude it into granules. The feeding section temperature of the twin-screw extruder is 150-160°C, the compression section temperature is 190-200°C, the metering section temperature is 200-210°C, the head temperature is 200-210°C, and the screw speed is 100r / min to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0045] Example 5

[0046] Preparation of polylactic acid / montmorillonite / nanocellulose whisker composites:

[0047] (1) Polylactic acid is dissolved in 1,4-dioxane, and then N-allyl-N,N-bis(trimethylsilyl)amine and diisopropylbenzene peroxide are added, and the mixture is heated under reflux for reaction until the viscosity of the system no longer changes. After the reaction is completed, the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine are recovered by vacuum distillation, and the concentrate is washed with water and vacuum dried to obtain graft-modified polylactic acid. The amount of N-allyl-N,N-bis(trimethylsilyl)amine added is 15% of the mass of the polylactic acid, and the amount of diisopropylbenzene peroxide added is 0.3% of the mass of the polylactic acid.

[0048] (2) The grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and silane coupling agent KH550 prepared above are fully mixed to obtain a mixture, wherein the amount of montmorillonite added is 3% of the mass of the grafted modified polylactic acid, the amount of nanocellulose whiskers added is 3% of the mass of the grafted modified polylactic acid, and the amount of silane coupling agent KH550 added is 3% of the mass of the grafted modified polylactic acid.

[0049] (3) Add the prepared mixture into a twin-screw extruder, melt and plasticize it, and then extrude it into granules. The feeding section temperature of the twin-screw extruder is 150-160°C, the compression section temperature is 190-200°C, the metering section temperature is 200-210°C, the head temperature is 200-210°C, and the screw speed is 100r / min to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material.

[0050] Comparative Example 1

[0051] The N-allyl-N,N-bis(trimethylsilyl)amine in Example 3 was replaced with allyltrimethoxysilane of the same mass, and the remaining preparation steps were the same as in Example 3.

[0052] Comparative Example 2

[0053] The N-allyl-N,N-bis(trimethylsilyl)amine in Example 3 was replaced with maleic anhydride of the same mass, and the remaining preparation steps were the same as in Example 3.

[0054] Comparative Example 3

[0055] Replace the graft-modified polylactic acid in Example 3 with the same mass of polylactic acid, that is, do not perform graft modification on polylactic acid, and the remaining preparation steps are the same as those in Example 3.

[0056] Melt spinning was carried out on the polylactic acid / montmorillonite / nano-cellulose whisker composites prepared in the above-mentioned examples and comparative examples respectively. The spinning temperature was 210 - 220 °C, the winding speed was 1000 m / min, the drawing temperature was 100 °C, and the drawing ratio was 3 times to obtain modified polylactic acid fibers.

[0057] Refer to the standard GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments" to test the elongation at break of the prepared modified polylactic acid fibers, and the results are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] It can be seen from the data in Table 1 that by using N-allyl-N,N-bis(trimethylsilyl)amine to graft-modify polylactic acid, the present invention can play a very good toughening role on polylactic acid, and the effect is significantly better than that of allyltrimethoxysilane and maleic anhydride.

[0062] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Preparation method of polylactic acid / montmorillonite / nanocellulose whisker composite material, Features: The method comprises the following preparation steps: (1) dissolving polylactic acid in 1,4-dioxane, then adding N-allyl-N,N-bis(trimethylsilyl)amine and an initiator, heating and refluxing for reaction, and after the reaction is completed, recovering the solvent and unreacted N-allyl-N,N-bis(trimethylsilyl)amine by vacuum distillation, washing the concentrate with water, and vacuum drying to obtain graft-modified polylactic acid; (2) fully mixing the grafted modified polylactic acid, montmorillonite, nanocellulose whiskers and a compatibilizer to obtain a mixture; (3) adding the above mixture into a twin-screw extruder, extruding and granulating after melting and plasticizing to obtain a polylactic acid / montmorillonite / nanocellulose whisker composite material; The added amount of the N-allyl-N,N-bis(trimethylsilyl)amine is 5-20% of the mass of the polylactic acid.

2. The preparation method according to claim 1, Features: The initiator is selected from one or more of benzoyl peroxide, dicumyl peroxide and di-tert-butyl peroxide.

3. The preparation method according to claim 1, Features: The added amount of the initiator is 0.1-1% of the mass of the polylactic acid.

4. The preparation method according to claim 1, Features: The added amount of the montmorillonite is 1-5% of the mass of the graft-modified polylactic acid.

5. The preparation method according to claim 1, Features: The added amount of the nano-cellulose whiskers is 1-5% of the mass of the grafted modified polylactic acid.

6. The preparation method according to claim 1, Features: The added amount of the compatibilizer is 1-10% of the mass of the graft-modified polylactic acid.

7. The preparation method according to claim 1, Features: The compatibilizer is a silane coupling agent.

8. A polylactic acid / montmorillonite / nanocellulose whisker composite material prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the polylactic acid / montmorillonite / nanocellulose whisker composite material according to claim 8 in textile processing.

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