阅读说明：本技术 一种耐水纳米纤维素薄膜及其制备方法 (Water-resistant nano cellulose film and preparation method thereof ) 是由 方志强 刘宇 胡稳 陈港 宁洪龙 于 2018-05-30 设计创作，主要内容包括：本发明公开了一种耐水纳米纤维素薄膜及其制备方法,属于生物基纳米材料领域。具体制备方法如下：1)以纳米纤维素为原料,将其分散液均匀的倾倒于培养皿中,并放置于恒温恒湿箱中干燥成凝胶；2)将纳米纤维素凝胶用酸溶液或者重金属盐溶液处理一段时间；3)将处理后的纳米纤维素凝胶用去离子水清洗后,继续放置于恒温恒湿箱中干燥,制得耐水纳米纤维素薄膜。本发明优点如下：(1)不含难以生物降解的添加剂；(2)工艺简单,无需额外的处理工艺(如热处理、纳米纤维素改性)；(3)保留纳米纤维素薄膜优异的机械和光学性能；(4)提升了纳米纤维素薄膜的热稳定性；(5)易于制备大尺寸、平整的纳米纤维素薄膜。(The invention discloses a water-resistant nano cellulose film and a preparation method thereof, belonging to the field of bio-based nano materials. The preparation method comprises the following steps: 1) uniformly pouring the dispersion liquid of nano-cellulose serving as a raw material into a culture dish, and placing the culture dish into a constant temperature and humidity box to dry the culture dish into gel; 2) treating the nano cellulose gel with acid solution or heavy metal salt solution for a period of time; 3) and (3) washing the treated nano cellulose gel with deionized water, and continuously placing the nano cellulose gel in a constant temperature and humidity box for drying to obtain the water-resistant nano cellulose film. The invention has the following advantages: (1) does not contain additives which are difficult to biodegrade; (2) the process is simple, and additional treatment processes (such as heat treatment and nanocellulose modification) are not needed; (3) the excellent mechanical and optical properties of the nano cellulose film are reserved; (4) the thermal stability of the nano cellulose film is improved; (5) the large-size and flat nano-cellulose film is easy to prepare.)

1. A preparation method of a water-resistant nano cellulose film is characterized by comprising the following steps:

(1) Preparing nano cellulose dispersion liquid by using plant fibers as raw materials through chemical pretreatment and mechanical treatment;

(2) Uniformly pouring the nano-cellulose dispersion liquid into a culture dish;

(3) Placing the culture dish containing the nano-cellulose dispersion liquid in a constant temperature and humidity box, drying the culture dish into gel, and adding an acid solution or a heavy metal salt solution for treatment;

(4) and (3) washing the nano cellulose gel treated by the acid solution or the heavy metal salt solution with water, and then continuously placing the nano cellulose gel in a constant temperature and humidity box for drying to obtain the water-resistant nano cellulose film.

2. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the plant fiber in the step (1) is softwood pulp, hardwood pulp, non-wood pulp, waste paper pulp, fluff pulp or cotton pulp.

3. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the chemical pretreatment in the step (1) is more than one of a TEMPO oxidation system pretreatment method, a deep eutectic solvent treatment method, a sulfonation reaction treatment method and an alkali treatment method; the mechanical treatment refers to more than one treatment of a high-pressure micro-jet method, a high-pressure homogenizing method, a high-concentration disc grinding method and a high-strength ultrasonic crushing method.

4. the method for preparing a water-resistant nanocellulose film according to claim 3, characterized in that: the substances used in the deep eutectic solvent treatment method are choline chloride and urea; the materials used in the sulfonation treatment process are periodate and bisulfite.

5. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the mass concentration of the nano cellulose dispersion liquid in the step (1) is 0.5-1%.

6. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the mass concentration of the gel in the step (3) is 2-4%.

7. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the acid solution in the step (3) is more than one of sulfuric acid, hydrochloric acid and acetic acid.

8. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: the heavy metal salt in the step (3) is more than one of calcium salt, chromium salt and magnesium salt.

9. The method for preparing a water-resistant nanocellulose film according to claim 1, characterized in that: and (4) drying conditions in the constant temperature and humidity box are as follows: the humidity is 40-80%, and the temperature is 30-50 ℃.

10. The water-resistant nanocellulose film prepared by the preparation method of any one of claims 1 to 9, characterized in that the water-resistant nanocellulose film has a transparency of more than 85%, a surface roughness of 1.5 to 10nm, a tightness of 1.0 to 1.2g/cm ³, a tensile strength of 80 to 200MPa, and is only increased by 1 to 3% in the length, width and thickness directions by soaking in water for 24 to 72 hours.

Technical Field

The invention belongs to the technical field of water-resistant nano materials and papermaking, and particularly relates to a water-resistant nano cellulose film and a preparation method thereof.

Background

The nano-cellulose film is a film material prepared from nano-cellulose, and has excellent light transmittance and mechanical properties, high thermal stability, low thermal expansion, low oxygen permeability and other excellent properties. [ Okahisa Y, Yoshida A, Miyaguchi S, et al, optical transfer wood-cellulose nanocomposite as abase substrate for flexible organic light-emitting diode display [ J ]. compositions Science and Technology, 2009, 69(11): 1958-

Klemm D, Kramer F, Moritz S, et al nanocell metals, A new family of nature-based materials [ J ]. Angewandte chemical International Edition, 2011, 50(24): 5438-5466] as a novel green material, and the nanocellulose film has potential application in the fields of transparent electronic devices and green packaging materials. Syverud K, Stenius P, Strength and barrier properties of MFC films [ J ]. Cellulose, 2009, 16(1): 75 ], however, due to the high hydrophilicity of nanocellulose (especially nanocellulose prepared by TEMPO oxidation pretreatment method), the nanocellulose film absorbs water and swells strongly under humid conditions, resulting in a sharp drop of the performance. The hydrophilicity of the nanocellulose film greatly limits its application field. [ Ben i z A J, Torres-Rendon J, Poutanen M, et al, Humidity and molecular structure mechanical properties and deformation modes of native cell nanofibers [ J ]. Biomacromolecules, 2013, 14(12): 4497 and 4506 ]

for example, some Hydrophobic groups are introduced to the Surface of nanocellulose by acetylation, silylation, esterification and graft copolymerization reactions [ Rodionova G, Lenes M, Eriksen Ø, et al. Surface Chemical modification of micro fibrous fibers ] while these reactions require the use of some flammable, non-environmentally friendly organic solvents that are detrimental to human health and add additional procedures that increase the cost of nanocellulose, furthermore these Chemical reactions generally damage the crystalline structure of nanocellulose, leading to a decrease in the properties of nanocellulose-based materials [ aromatic A, Cellulose L, fiber B, Cellulose fibers ] and Cellulose fibers ] through the covalent crosslinking reaction of Cellulose fibers [ fibers J, Cellulose fibers ] and the formation of Cellulose fibers [ fibers ] fibers, Cellulose fibers ] through the covalent crosslinking reaction of Cellulose fibers [ fibers ] and Cellulose fibers [ fibers ] A, Cellulose fibers ] and Cellulose fibers [ fibers ] through Chemical crosslinking reaction of Cellulose fibers [ fibers ] A, Cellulose fibers ] and Cellulose fibers [ fibers ] through Chemical crosslinking reaction of Cellulose fibers [ fibers ] and Cellulose fibers [ fibers ] and Cellulose fibers ] through the covalent reaction of Cellulose fibers [ fibers ] forming a surfactant, Cellulose fibers [ fibers ] and Cellulose fibers [ fibers ] through the covalent reaction of Cellulose fibers [ fibers ] and Cellulose fibers [ fibers ] through the formation of Cellulose fibers [ Chemical crosslinking reaction of Cellulose fibers [ fibers ] and Cellulose ester [ fibers ] through the reaction of Cellulose ester Chemical reaction of Cellulose ester [ fibers ] and Cellulose ester [ fibers ] covalent reaction [ fibers ] and Cellulose ester [ fibers ] forming a Cellulose ester [ fibers ] and Cellulose ester [ fibers ] Cellulose ester [ fibers [ Chemical reaction [ Cellulose ester [ fibers ] and Cellulose ester [ fibers ] Cellulose ester [ fibers ] and Cellulose ester [ fibers ] through the reaction [ Cellulose ester [ Chemical reaction [ Cellulose ester ] and Cellulose ester [ Cellulose ester ] and Cellulose ester [ Cellulose ester

Toivonen M S, Kurki-Suonio S, Schacher F H, et al, Water-resist, transparent nanopaper by physical cross-linking with a chitosan [ J ]. Biomacromolecules, 2015, 16(3): 1062-1071 ], however, some of these methods have complicated preparation processes and long preparation time, and some substances which are difficult to be biodegraded are not environment-friendly.

disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art and provides a water-resistant nano cellulose film and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme.

A preparation method of a water-resistant nano cellulose film comprises the following steps:

(1) Preparing nano cellulose dispersion liquid by using plant fibers as raw materials through chemical pretreatment and mechanical treatment;

(2) Uniformly pouring the nano-cellulose dispersion liquid into a culture dish;

(3) Placing a culture dish containing the nano-cellulose dispersion liquid in a constant temperature and humidity box, casting a film, drying the film into gel, and adding an acid solution or a heavy metal salt solution for treatment for a period of time;

(4) And (3) washing the nano cellulose gel treated by the acid solution or the heavy metal salt solution by using deionized water, and then continuously placing the nano cellulose gel in a constant temperature and humidity box for casting and drying to obtain the waterproof nano cellulose film.

Preferably, the plant fiber in the step (1) is softwood pulp, hardwood pulp, non-wood pulp, waste paper pulp, fluff pulp and cotton pulp.

Further optimized, the following steps are carried out: the chemical pretreatment in the step (1) is more than one of a TEMPO oxidation system pretreatment method, a deep eutectic solvent treatment method, a sulfonation reaction treatment method and an alkali treatment method; the mechanical treatment refers to more than one treatment of a high-pressure micro-jet method, a high-pressure homogenizing method, a high-concentration disc grinding method and a high-strength ultrasonic crushing method.

in a further optimization, the deep eutectic solvent treatment method uses choline chloride and urea as materials.

Further preferably, the sulfonation reaction treats periodate and bisulfite as the materials used.

Further preferably, the mass concentration of the nano-cellulose dispersion liquid in the step (1) is 0.5-1%.

Further preferably, the mass concentration of the gel in the step (3) is 2-4%.

Preferably, the acid solution in step (3) is one or more of organic acid and inorganic acid (such as sulfuric acid, hydrochloric acid or acetic acid).

Preferably, the heavy metal salt in step (3) is one or more of calcium salt, chromium salt and magnesium salt.

Further optimally, the drying conditions in the constant temperature and humidity box in the steps (3) and (4) are that the humidity is 40-80%, and the temperature is 30-50 ℃.

The waterproof nanocellulose film prepared by the preparation method is free from wrinkling and bubbles, the transparency of the waterproof nanocellulose film is more than 85%, the surface roughness is 1.5-10 nm, the tightness is 1.0-1.2g/cm ³, and the tensile strength is 80-200 MPa.

Compared with the prior art, the invention has the following beneficial effects:

(1) The nano cellulose film has excellent water resistance, and the size amplification of the nano cellulose film in the length direction, the width direction and the thickness direction is between 1 and 3 percent after the nano cellulose film is soaked in water for 24 hours.

(2) The film does not contain additives difficult to biodegrade, and can realize 100 percent biodegradation after the film is discarded;

(3) The process is simple, and additional treatment processes (such as heat treatment and nanocellulose modification) are not needed;

(4) The excellent mechanical and optical properties of the nano cellulose film are reserved;

(5) The thermal stability of the nano cellulose film is improved;

(6) The large-size and flat nano-cellulose film is easy to prepare.

Detailed Description

Specific embodiments of the present invention are further described below with reference to examples, but the scope of the present invention is not limited thereto.

The light transmittance of the nano-cellulose film is determined according to the national standard GB/T2410-2008; the tensile strength test adopts GB/T1040-2006 national standard test; the surface roughness was characterized using an atomic force microscope.