Preparation method and application of cellulose film

Abstract

The invention provides a preparation method and application of a cellulose film. The preparation method comprises the following steps: dissolving cellulose pulp in an organic alkali ionic liquid, defoaming, coating, cooling, immersing in a coagulating bath consisting of two anti-solvents with different polarities for regeneration forming, and washing and drying to obtain the cellulose light management film. The cellulose raw material and the green and environment-friendly organic alkali ionic liquid are used, so that the environmental pollution problem caused by a petroleum-based light management material and the safety problems of flammable and combustible volatile organic solvents and the like can be effectively solved. According to the technology, continuous controllable preparation of cellulose haze is achieved by regulating hydrogen bond competition through anti-solvent polarity difference, the whole technological process is simple, stable and efficient, and the prepared light management film can be widely applied to the fields of solar cells, intelligent windows, LEDs, laser illumination and the like.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of cellulose functionalized materials, and in particular to a preparation method and application of a cellulose film. Background Art

[0002] With the continuous advancement of science and technology, light is widely used in many fields such as information, energy, and medicine. From high-speed optical communication networks to efficient solar photovoltaic power generation, to precise optical medical equipment, the effective use of light has become the key to promoting the development of various fields. Light management technology has emerged as the times require. It controls the propagation, absorption, reflection, and scattering of light through the design and optimization of optical structures and material properties, thereby improving the utilization efficiency of light energy and meeting specific optical performance requirements.

[0003] As a key material for achieving light management functions, the development of research and preparation technology of light management films has attracted much attention. However, there are many problems with the traditional preparation methods of light management films. On the one hand, the light management performance of the prepared film is difficult to achieve an ideal state, such as the haze and transmittance cannot be taken into account at the same time, which makes it impossible to use it in some application scenarios that require strict optical performance. On the other hand, the preparation process of the film is complicated and costly, which limits its large-scale production and wide application. In addition, the petroleum-based raw materials used in traditional processes are not conducive to the sustainable development of the ecological environment. Therefore, the development of a green, environmentally friendly, simple, efficient, low-cost and large-scale production technology for light management films is of great significance to promoting the development of the optoelectronics industry, the energy industry and related emerging industries.

[0004] Haze is a key performance indicator in light management films. It determines the degree of light scattering, which in turn affects the optical performance of the material in different scenarios. At present, the commonly used haze materials are still traditional petroleum-based materials (such as polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polypropylene, etc.). However, the existing petroleum-based haze materials still cannot overcome the problem of achieving high haze while ensuring high transmittance, and it is difficult to achieve continuous adjustment of haze. Although these traditional materials have certain flexibility and easy processing, they have a high thermal expansion coefficient and are prone to yellowing and aging under long-term light or high temperature environments, resulting in degradation of optical properties, difficulty in recycling and degradation, and an increasingly deteriorating ecological environment. It is difficult to meet diverse needs in complex application scenarios.

[0005] Cellulose, the most abundant natural polymer on earth, is mainly extracted from plants such as wood, cotton, bamboo and grass, and has the advantages of biocompatibility, biodegradability and low cost. Therefore, using cellulose to prepare light management film materials and achieving high light transmittance and controllable haze of the film can not only break through the bottleneck of traditional materials in terms of performance and environmental protection, but also meet the urgent needs of modern technology for high performance, low cost and green environmental protection of materials, which has strong theoretical significance and application value. Summary of the invention

[0006] Based on the above technical problems, the purpose of the present invention is to provide a preparation method and application of a cellulose film, which can achieve continuous adjustable haze while ensuring that the film has high light transmittance.

[0007] The present invention provides a method for preparing a cellulose film, comprising the following steps: The cellulose pulp is dissolved in an organic alkaline ionic liquid, and a homogeneous cellulose solution is obtained by high-temperature vacuum degassing; The cellulose solution is evenly coated on a glass plate, and after the solution is cooled to room temperature, it is immersed in a coagulation bath composed of two anti-solvents with different polarities to regenerate and shape, thereby obtaining a regenerated cellulose wet gel; The regenerated cellulose wet gel is repeatedly washed with deionized water and dried at a constant temperature to obtain a cellulose light management film.

[0008] By means of the above technical solution, the beneficial effects of the present invention are: The present invention utilizes organic alkaline ionic liquids to dissolve cellulose. Compared with traditional organic solvents, this type of solvent system has the advantages of low vapor pressure, high chemical stability, strong resistance to metal corrosion, and high cellulose dissolution efficiency. It can solve the problems of environmental pollution, flammable and explosive safety hazards in the production process to a large extent, and is in line with the development trend of green chemistry.

[0009] The present invention effectively utilizes a coagulation bath composed of two antisolvents of different polarities to promote the self-assembly aggregation of cellulose molecular chains under the antisolvent hydrogen bond competition effect to construct a cellulose multi-level hydrogen bond network. Specifically, it is preferred that deionized water with a stronger polarity and a class of alcohols with a weaker polarity form the coagulation bath, and the hydrogen bonding between the antisolvent, the organic base ionic liquid and the cellulose is regulated by the polarity difference. The water with a stronger polarity will preferentially solvate the anions and cations of the ionic liquid, while the preferred alcohol weakens the solvation effect by hydrogen bonding with water molecules, thereby affecting the reorganization of hydrogen bonds between / within the cellulose molecular chains and the construction of the supramolecular structure. The synergistic effect of the two antisolvents of different polarities results in differences in the aggregated structure and spatial arrangement of cellulose, and the surface of the constructed film presents defect structures of different forms, resulting in different degrees of scattering effects on the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a graph showing the haze variation of the cellulose light management films prepared in Examples 1-4 and Comparative Example 1; Figure 2 It is a curve diagram of light transmittance variation of cellulose light management films prepared in Example 1 and Comparative Example 1; Figure 3 Microscopic morphology of cellulose light management films prepared in Example 3 and Comparative Example 1; Figure 4 This is a comparison chart of light regulation by the cellulose light management films prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0011] In the following description, different "one embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0012] Unless otherwise defined, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

[0013] The methods in the following examples are conventional methods unless otherwise specified; the materials or reagents in the following examples are commercially available unless otherwise specified.

[0014] The present invention is further described below with specific embodiments, but is not intended to be limiting of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0015] A method for preparing a cellulose film proposed in the present application comprises the following steps: The cellulose pulp is dissolved in an organic alkaline ionic liquid, and a homogeneous cellulose / ionic liquid solution is obtained by high-temperature vacuum degassing; the cellulose solution is evenly coated on a glass plate by a coating machine, and after the solution is cooled to room temperature, it is immersed in a coagulation bath composed of two anti-solvents with different polarities for regeneration and molding to obtain a regenerated cellulose wet gel; the regenerated cellulose wet gel is repeatedly washed with deionized water, and a regenerated cellulose film is obtained by constant temperature drying.

[0016] According to the above method, by adjusting the ratio of two anti-solvents with different polarities, a cellulose film with wide-range haze and high transmittance can be obtained.

[0017] Preferably, the organic base ionic liquid is at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene acetate, 1,8-diazabicyclo[5.4.0]undec-7-ene methoxy acetate or 1,8-diazabicyclo[5.4.0]undec-7-ene ethoxy acetate.

[0018] Preferably, the cellulose pulp has a degree of polymerization of 500-1500, and an α-cellulose content of more than 90%; more preferably, the cellulose pulp has a degree of polymerization of 500-650, and an α-cellulose content of more than 95%.

[0019] Preferably, the concentration of the cellulose solution is 2-6 wt %, and the preferred concentration is 3-4 wt %; the dissolution temperature is 80-120° C., and the preferred dissolution temperature is 80-90° C.; the vacuum degassing temperature is 90° C., and the degassing time is 1-4 h.

[0020] Preferably, in the coating process, the coating speed is 0.1-1.0 m / min, and the coating thickness is 100-500 μm.

[0021] Preferably, the coagulation baths composed of two antisolvents with different polarities are coagulation baths composed of deionized water with stronger polarity and alcohol with weaker polarity respectively; the alcohol comprises one of ethanol, propanol, n-propanol, isopropanol, n-propanol, isobutanol or n-butanol.

[0022] Preferably, the ratio of the two anti-solvents with different polarities is adjusted such that the weight of water is 10 to 90 parts per 100 parts by weight of the coagulation bath.

[0023] Preferably, the film thickness is 30-55 μm, the haze at a wavelength of 550 nm is 8-75%, the transmittance is 89-92%, and the haze can be controlled in a wide range. Figure 1 and Figure 2 It can flexibly adjust the degree of light scattering of the film according to needs, and combine with the high light transmittance of the film to achieve its specific optical effect and meet the requirements of different scenarios, such as solar cells, smart windows, LED and laser lighting.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows.

[0025] Example 1 In parts by weight, 5 parts of cellulose pulp with a degree of polymerization of 600 and 95 parts of 1,8-diazabicyclo[5.4.0]undec-7-ene acetate were weighed and mixed at 90°C and stirred evenly. After the cellulose was completely dissolved, it was placed in a vacuum drying oven at 90°C for 1 h to remove bubbles in the solution, thereby obtaining a homogeneous cellulose solution; The cellulose solution was evenly coated on the glass plate at a speed of 0.1 m / min using a coating machine, with a coating thickness of 300 μm; after the solution on the glass plate cooled to room temperature, it was immersed in a coagulation bath consisting of 90 parts of deionized water and 10 parts of n-propanol to coagulate, and then repeatedly washed with deionized water and dried at a constant temperature of 50°C to obtain a cellulose light management film with a haze of 74.7% and a transmittance of 89.2%. Figure 4 As shown, using it in home lighting equipment increases the diffusion of light and makes the lighting range wider.

[0026] Example 2 The same as Example 1, except that the cellulose solution is immersed in a coagulation bath composed of 70 parts of deionized water and 30 parts of n-butanol to coagulate and form a cellulose light management film with a haze of 39.3% and a transmittance of 90.7%.

[0027] Example 3 The same as Example 1, except that the cellulose solvent is 1,8-diazabicyclo[5.4.0]undec-7-ene methoxyacetate; the cellulose solution is immersed in a coagulation bath consisting of 50 parts of deionized water and 50 parts of n-propanol to coagulate and form a cellulose light management film with a haze of 27.3% and a transmittance of 90.0%. Figure 3 As shown, there are a large number of micron-scale concave and convex structures on the surface of the film, which causes the incident light to be refracted and reflected multiple times on the surface, dispersing the direction of the light and helping to improve its scattering effect on light.

[0028] Example 4 The same as Example 1, except that the cellulose solution is immersed in a coagulation bath composed of 30 parts of deionized water and 70 parts of n-propanol to coagulate and form a cellulose light management film with a haze of 17.8% and a transmittance of 89.5%.

[0029] Comparative Example 1 The same as Example 1, except that the cellulose solution is immersed in a coagulation bath composed of 100 parts of n-propanol to coagulate and form a cellulose light management film with a haze of 8.1% and a transmittance of 91.5%.

[0030] Comparative Example 2 The same as Example 1, except that the cellulose solution was immersed in a coagulation bath consisting of 100 parts of deionized water for coagulation and the prepared film was white and brittle and could not be used.

[0031] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0032] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0033] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a cellulose film, characterized in that: The following steps are involved: The cellulose pulp is dissolved in an organic alkaline ionic liquid, and a homogeneous cellulose solution is obtained by high-temperature vacuum degassing; The cellulose solution is evenly coated on a glass plate, and after the solution is cooled to room temperature, it is immersed in a coagulation bath composed of two anti-solvents with different polarities to regenerate and shape, thereby obtaining a regenerated cellulose wet gel; The regenerated cellulose wet gel is repeatedly washed with deionized water and dried at a constant temperature to obtain a cellulose light management film.

2. The method for preparing a cellulose film according to claim 1, characterized in that: The organic base ionic liquid is at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene acetate, 1,8-diazabicyclo[5.4.0]undec-7-ene methoxy acetate or 1,8-diazabicyclo[5.4.0]undec-7-ene ethoxy acetate.

3. The method for preparing a cellulose film according to claim 1 or 2, characterized in that: The cellulose pulp has a polymerization degree of 500-1500 and an α-cellulose content of more than 90%.

4. The method for preparing a cellulose film according to claim 3, characterized in that: The dissolution temperature is 80-120°C; the vacuum degassing temperature is 90°C, the degassing time is 1-4h, and the cellulose solution concentration is 2-6wt%.

5. The method for preparing a cellulose film according to claim 1, characterized in that: The coagulation baths are respectively composed of deionized water with a stronger polarity and alcohol with a weaker polarity; the alcohol includes one of ethanol, propanol, n-propanol, isopropanol, n-butanol or isobutanol.

6. The method for preparing a cellulose film according to claim 5, characterized in that: The ratio of the two anti-solvents with different polarities is: based on 100 parts by weight of the coagulation bath, the weight of deionized water is 10-90 parts.

7. The method for preparing a cellulose film according to claim 1, characterized in that: During the coating process, the coating speed is 0.1-1.0 m / min, and the coating thickness is 100-500 μm.

8. The method for preparing a cellulose film according to claim 1, characterized in that: The cellulose light management film has a thickness of 30-55 μm, a haze of 8-75% at a wavelength of 550 nm, and a light transmittance of 89-92%.

9. A cellulose film prepared according to the method according to any one of claims 1 to 8.

10. Use of the cellulose film according to claim 9 in solar cells, smart windows, LED and laser lighting.

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