CN113831560B - Device and method for preparing high-performance nano cellulose membrane by macro wet method - Google Patents

Abstract

The invention belongs to the field of cellulose wet preparation and the technical field of light industrial machinery design, and specifically discloses a method for preparing nano-cellulose film by a macro wet method and a precision injection compression molding device. Inject the nanocellulose suspension solution into the fixed mold, and then vacuumize the inner cavity of the fixed mold, and at the same time, the hydraulic slider at the movable mold moves to the fixed mold direction to compress the nanocellulose suspension solution; the water discharged by the compression is vacuumized The device is drawn out and introduced into the drainage collection device. After the water is discharged, the mold is opened, and then the nanocellulose film is ejected from the cavity on the fixed mold, and then dried, stretched and shaped in sequence to obtain the nanometer cellulose film. Cellulose film. The invention can significantly improve the efficiency of preparing cellulose membrane by wet forming, and can improve the morphology of the membrane by adjusting the time, temperature, pressure and other parameters of vacuum pressure filtration, so as to realize the mass production of nanocellulose suspension wet membrane formation .

Description

A device and method for preparing high-performance nanocellulose membranes by a macro-scale wet method

technical field

The invention belongs to the field of cellulose wet preparation and the technical field of light industrial machinery design, and in particular relates to a method for preparing nano-cellulose film by a macro wet method and a precision injection compression molding device thereof.

Background technique

Compared with traditional methods such as spin coating, film casting, sol-gelation, electrospinning and track etching, the present invention intends to use precision Injection pressure wet film formation-adjustable water evaporation and drying strategy, based on precision injection pressure-vacuum drainage-thermal stretching method for macro-preparation of nanocellulose membranes, with simple operation, process control, uniform film thickness and high efficiency Forming and other advantages will promote the application of high-performance cellulose membranes in the field of battery separators, provide new methods for green, efficient and intelligent manufacturing of new energy industries, and further promote new principles and methods of polymer processing theoretical and technical developments. The invention aims to provide a precision injection compression molding device with high production efficiency, stable production process, and the ability to prepare nanocellulose membranes through pressurized vacuum filtration.

The traditional cellulose film preparation method adopts the solution method, that is, dissolves cellulose in solvents such as ionic liquids, alkali solutions, and organic oxides to form a homogeneous solution system, and then obtains it by forming in a coagulation bath, solvent replacement, and self-volatility. Small batches of cellulose membranes. Through porogens, nano-particles such as graphene and silica, and changing the ratio of the dispersion medium, a cellulose membrane material with adjustable porosity, high mechanical strength and ion channels is obtained to realize the green color of the cellulose membrane. , Preliminary exploration of high-efficiency and macro-scale preparation (Cellulose, 2015, 22(5): 2983-2992). Sehaqui et al. (Biomacromolecules, 2011, 12(10): 3638-3644) made nanocellulose hydrogel by enzymatic pretreatment, TEMPO alkaline oxidation treatment and mechanical treatment of coniferous wood fiber, which was prepared by supercritical carbon dioxide drying method Nanopaper with a porous structure. Chun et al. (Journal of Materials Chemistry, 2012,22(32):16618-16626) homogenized the eucalyptus wood cellulose powder in the solvent of isopropanol/water for many times, and formed the cellulose film with hot pressing, because the film material Too brittle can cause cracking in flexible displays or touch screens. Based on the principle of phase inversion, the research group of Professor Chen Huanlin from Zhejiang University prepared nitrocellulose membranes by direct immersion method, steam induction method and dry method, and systematically investigated the mechanism of the influence of cellulose membrane forming methods on membrane structure and performance (China Paper, 2019( 9):59-68). Different from the above-mentioned membrane forming strategy, Professor Tang Aimin of South China University of Technology used nano-cellulose suspension as the base material, and achieved high Green Fabrication of Strong, High-Ion-Flux Cellulose Membranes. This wet film forming method has attracted much attention due to its advantages of environmental protection, simple operation, controllable process, uniform film thickness and high-efficiency forming. During the hot-press drying process of the wet film, with the slow evaporation of water, the nanocellulose fibers approach each other under the capillary action and finally form a dense network structure, which affects the pore performance.

Injection compression molding is a kind of injection molding of thermoplastic polymer melt into the mold cavity, and then short-stroke mold clamping compression (International communications in heat and mass transfer, 1998, 25 (7): 907-917), especially Partially pressurized injection molding compression (fine pressing), fully utilizes hydraulic devices such as mold sliders to achieve compression. The fine-pressed mold cavity can ensure that the pressure is evenly distributed in the two axial directions of the product surface, which can significantly improve the precision of the surface details, dimensional stability and production process repeatability of polyethylene, polypropylene and other polymer materials injection molded products (Applied Materials Today , 2019, 16:72-82).

In order to ensure the dimensional stability of the wet-process film and prepare a water-containing cellulose film with uniform size and high reproducibility and yield, the present invention designs a precision injection compression molding device for preparing nano-cellulose film, including a mold cavity design, vacuum system design and precision injection molding, etc.

Contents of the invention

In order to solve the above-mentioned technical problems, the primary purpose of the present invention is to provide a method for preparing nanocellulose membranes by a macro-scale wet method;

Another object of the present invention is to provide a precision injection compression molding device for the above-mentioned macro-scale wet preparation of nanocellulose membranes, so as to improve the high-value application and industrialization possibility of cellulose membranes.

The object of the present invention is achieved by the following methods:

A method for preparing cellulose film by a macro-scale wet method, mainly comprising the following steps:

Inject the nanocellulose suspension solution into the fixed mold, and then vacuumize the inner cavity of the fixed mold, and at the same time, the hydraulic slider at the movable mold moves to the fixed mold direction to compress the nanocellulose suspension solution; the water discharged from the compression is vacuumized The device is pulled out and introduced into the drainage collection device. After the water is discharged, the mold is opened, and then the nanocellulose film is ejected from the mold cavity on the fixed mold, and then dried, stretched and shaped in sequence to obtain the nanometer cellulose film. Cellulose film.

Preferably, the temperature of the fixed film and the movable mold is 40-80°C;

Preferably, the forward speed of the hydraulic slider is 0.5-2mm/min;

Preferably, the injection pressure when compressing the nanocellulose suspension solution is 70-120 MPa.

A device for preparing high-performance nanocellulose membranes by the above-mentioned macro-quantity wet method, including a precision injection machine, a pressurized suction filter mold, and a drying system;

The pressure suction filter mold includes a fixed mold, a movable mold, a vacuum device and a drainage collection device; the outlet of the precision injection machine is connected with the fixed mold; the movable mold contains a hydraulic module, and the hydraulic module is connected to the vacuum pump The device is connected; the vacuum device of the fixed mold is connected with the cavity of the fixed mold through a pipeline; the fixed mold and the movable mold have drains, and the drainage collecting device is connected with the fixed membrane and the movable mold through the drains; The drying system includes a heating device, a bidirectional stretching device and a sizing device connected in sequence, and the drying system is connected with a pressurized suction filter mold through a conveyor belt.

Preferably, the other end of the precision injection machine is connected to a storage tank, and the storage tank is equipped with a stirring paddle for fully mixing the raw materials.

Preferably, both the fixed mold and the movable mold have thermocouples for measuring mold temperature;

Preferably, a manipulator is provided at the connection between the pressurized suction filter mold and the drying system, and the manipulator is provided with a vacuum suction cup.

Under the prior art, the present invention has the following advantages and beneficial effects:

(1) Significantly improved the efficiency of wet forming to prepare cellulose film. Nanocellulose hydrogel has high viscosity, and the simple vacuum filtration has the disadvantages of long time, low production efficiency, and large production energy consumption.

Different from the method of only using vacuum to extract the water in the nanocellulose suspension solution, this set of molds can realize two-way vacuum drainage. There are vacuum devices on both the fixed mold and the movable mold, and the nanocellulose suspension The solution is compressed, which speeds up the water separation speed, which is more than 15 times that of the cellulose membrane prepared by ordinary vacuum filtration wet method.

(2) The microscopic morphology of the cellulose membrane prepared by the vacuum pressure filtration system is basically the same as that of the cellulose membrane obtained by ordinary vacuum filtration, the uniformity of the film thickness is improved, and the size of the membrane is adjustable. sex.

(3) Realize the mass production of nanocellulose suspension wet film formation.

(4) The morphology of the membrane can be improved by adjusting the time, temperature and pressure of vacuum pressure filtration, especially the construction of scientific principles based on temperature, shear field and viscosity and the optimization of detailed system parameters. The patent of this invention The purpose of improving the effect of filtering water and removing water while achieving the performance optimization and high preparation efficiency of the cellulose membrane is realized.

Description of drawings

Fig. 1 is the device for preparing high-performance nanocellulose membrane by macro-scale wet method according to the present invention.

Fig. 2 is a model diagram of fixed film and moving model in the device of the present invention for preparing high-performance nanocellulose film by macro-volume wet method.

Fig. 3 is the pressurized suction filtration mold device used in the rapid preparation of cellulose membrane by wet method in Example 1.

Fig. 4 is the viscosity-temperature variation curve of the nanocellulose suspension solution obtained in Example 1.

Figure 5 is the morphology of cellulose membranes under different molding methods, wherein Figure (a) is the vacuuming method in Comparative Example 1, and Figure (b) is the morphology of the cellulose membrane obtained by the compression-vacuum drainage method in Example 1.

detailed description

The purpose and technical solutions of the present invention will be described more clearly below in conjunction with the embodiments and accompanying drawings, and the described embodiments are only part of the embodiments of the present invention.

The device used in the embodiment to prepare high-performance nanocellulose membrane by macro-quantity wet method includes a precision injection machine, a pressurized suction filter mold and a drying system;

The pressure suction filter mold includes a fixed mold, a movable mold, a vacuum device and a drainage collection device; the outlet of the precision injection machine is connected with the fixed mold; the movable mold contains a hydraulic module, and the hydraulic module is connected to the vacuum pump The device is connected; the vacuum device of the fixed mold is connected with the cavity of the fixed mold through a pipeline; the fixed mold and the movable mold have drains, and the drainage collecting device is connected with the fixed membrane and the movable mold through the drains; The drying system includes a heating device, a bidirectional stretching device and a sizing device connected in sequence, and the drying system is connected with a pressurized suction filter mold through a conveyor belt.

As a preference, the other end of the precision injection machine is connected to a storage tank, and the storage tank is equipped with a stirring paddle for fully mixing the nanocellulose suspension solution. The dimensions of the fixed film and the movable mold are independently 40×40×15 cm, and both have thermocouples for measuring the mold temperature; the size of the fixed film cavity is 30×30×1 cm. In the fixed mold and the movable mold, a manipulator is provided at the joint between the pressurized suction filter mold and the drying system, and the manipulator is provided with a vacuum suction cup for absorbing the cellulose film ejected from the mold cavity on the fixed mold, and Transfer it to the conveyor belt.

The method for preparing cellulose film by the macro-scale wet method described in the embodiment is realized by the above-mentioned device, and mainly includes the following steps:

The nanocellulose suspension solution is injected into the fixed mold by a precision injection machine, and then the inner cavity of the fixed mold is evacuated, and at the same time, the hydraulic slider at the movable mold moves toward the fixed mold direction to compress the nanocellulose suspension solution; The water in the cellulose suspension solution is drawn out by a vacuum device and introduced into the drainage collection device. After the water is discharged, the mold is opened, and then the nanocellulose film is ejected from the mold cavity on the fixed mold, transferred to the conveyor belt and Sent to the drying system for drying, stretching and setting treatment to obtain the nanocellulose film.

Preferably, the temperature of the fixed film and the movable mold is 40-80° C.; the advancing speed of the hydraulic slider is 0.5-2 mm/min; the injection pressure when compressing the nanocellulose suspension solution is 70-120 MPa.

Example 1

In the pressurized suction filter mold equipment used in this embodiment, the sealing plug is a movable mold, the sand core funnel is a fixed mold, and the plunger of the hydraulic press is a hydraulic module. First, pour the quantitative nanocellulose suspension into the sand core funnel, use the sealing plug to seal the sand core funnel, and then press the sealing plug through the plunger of the hydraulic press, and at the same time turn on the vacuum pump, and perform compression and vacuum drainage at the same time. The temperature of the fixed film and the movable mold is 60°C, and the advancing speed of the plunger is 1mm/min;

The pressurized suction filtration mold device used in this embodiment is shown in FIG. 3 .

Example 2

The size of the fixed membrane and the movable mold in the pressurized suction filtration mold device for preparing cellulose membrane in this embodiment is 40×40×15 cm, the cavity size of the fixed mold is 30×30×1 cm, and the temperature of the nanocellulose suspension is 60°C, injection pressure 100MPa, injection volume 900ml, mold temperature 60°C, hydraulic slider advance speed 1mm/min, vacuum filtration for 8 minutes, open the mold and take out the cellulose film.

Comparative example 1

The vacuum filtration device in Example 1 was used, but no sealing plug was used, and no hydraulic press was used for compression, and the nanocellulose suspension was only vacuumed by a vacuum pump, and other experimental parameters were the same as in Example 1.

Compared with the way of only vacuuming in Comparative Example 1, when the pressurized suction filter mold is used in Example 1, the separation speed of nanocellulose and water is shortened from 10 hours to 20 minutes, and the production efficiency is significantly improved. Figure 5 shows the morphology of cellulose membranes under the two molding methods of vacuuming (a) and compression-vacuum drainage (b). It can be seen from the figure that the microscopic morphology of the cellulose membranes prepared by these two molding methods is basically the same. It can be seen that compression-vacuum drainage does not change the microstructure of the membrane while improving the production efficiency of the cellulose membrane.

Figure 3 is the viscosity-temperature variation curve of the nanocellulose suspension solution. In this example, the viscosity of the nanocellulose suspension solution at different temperatures (20-60° C.) was tested.

The viscosity of the nanocellulose suspension decreases significantly with the increase of temperature, and its viscosity drops from 42mPa·s at 20°C to 28mPa·s at 60°C. Therefore, the nanocellulose suspension can be properly increased during the vacuum compression process. temperature, thereby improving the separation efficiency of water.

The above-mentioned embodiment is a preferred implementation mode of the present invention, but the implementation mode of the present invention is not limited by the above-mentioned embodiment, and any person familiar with the technical field can think of changes and modifications without departing from the spirit and principle of the present invention. , replacement, combination, and simplification, all should be equivalent replacement methods, and should all be covered within the protection scope of the present invention.

Claims (4)

1. A method for preparing a cellulose membrane by a macro wet method is characterized by mainly comprising the following steps:

injecting the nano-cellulose suspension solution into the fixed die, vacuumizing the inner cavity of the fixed die, and simultaneously moving the hydraulic slide block at the movable die to the direction of the fixed die to compress the nano-cellulose suspension solution; pumping out the compressed and discharged moisture by a vacuumizing device, guiding the moisture into a drainage collecting device, opening the die after the moisture is discharged, then ejecting the nano cellulose membrane from a die cavity on the fixed die, and sequentially drying, stretching and shaping to obtain the nano cellulose membrane;

the temperature of the fixed die and the movable die is 40 to 80 ℃;

the advancing speed of the hydraulic slide block is 0.5 to 2mm/min;

the injection molding pressure for compressing the nano-cellulose suspension solution is 70 to 120MPa.

2. An apparatus for realizing macroscopic quantity wet method preparation of cellulose membrane according to claim 1, which is characterized by comprising a precise injection machine, a pressure suction filtration mould and a drying system;

the pressurizing and suction filtration mold comprises a fixed mold, a movable mold, a vacuumizing device and a drainage collecting device; the discharge hole of the precision injection machine is connected with the fixed die; the movable mold comprises a hydraulic module, and the hydraulic module is connected with a vacuumizing device; the vacuumizing device of the fixed die is connected with the cavity of the fixed die through a pipeline; the fixed die and the movable die are both provided with water outlets, and the drainage collecting device is connected with the fixed die and the movable die through the water outlets; the drying system comprises a heating device, a biaxial stretching device and a shaping device which are sequentially connected, and is connected with the pressurizing and suction filtration die through a conveyor belt.

3. The apparatus of claim 2, wherein: the other end of the precision injection machine is connected with a storage tank, and a stirring paddle is matched in the storage tank and used for fully mixing raw materials.

4. The apparatus of claim 2, wherein: thermocouples are arranged in the fixed die and the movable die and are used for measuring the temperature of the die; and a manipulator is arranged at the joint of the pressurizing and suction filtration die and the drying system, and is provided with a vacuum chuck.

Images