阅读说明：本技术 一种耐水、透明纤维素基薄膜及其制备方法 (Water-resistant transparent cellulose-based film and preparation method thereof ) 是由 方志强 胡稳 刘宇 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、透明纤维素基薄膜及其制备方法,属于纤维素基薄膜的防水领域。具体制备方法如下：(1)将纳米纤维素分散体或纤维素衍生物溶液通过高分子溶胶浇铸法或真空过滤制备成透明纤维素基薄膜；(2)再将步骤(1)中的透明纤维素基薄膜浸渍于纯冰乙酸中,在超声作用下进行离子交换反应；之后将反应后的纤维素基薄膜用有机溶剂进行清洗,获得耐水、透明纤维素基薄膜。在水中浸泡24~72 h,其吸水率介于25~35%,厚度增大12~15%,长度和宽度增大4~8%,湿抗张强度15~30 MPa,在可见光区透光率介于90~91%之间。本发明涉及的耐水处理工艺不仅简单,而且保留了薄膜优异的透明度。(The invention discloses a waterproof and transparent cellulose-based film and a preparation method thereof, belonging to the field of water prevention of cellulose-based films, and the preparation method comprises the following steps of (1) preparing a transparent cellulose-based film from a nano cellulose dispersion or a cellulose derivative solution by a polymer sol casting method or vacuum filtration, (2) immersing the transparent cellulose-based film in the step (1) in pure glacial acetic acid to perform an ion exchange reaction under the action of ultrasound, then cleaning the reacted cellulose-based film by using an organic solvent to obtain the waterproof and transparent cellulose-based film, and immersing the cellulose-based film in water for 24 ~ 72 h, wherein the water absorption rate is 25 ~ 35%, the thickness is increased by 12 ~ 15%, the length and the width are increased by 4 ~ 8%, the wet tensile strength is 15 ~ 30 MPa, and the light transmittance in a visible light region is between 90 ~ 91%.)

1. A preparation method of a waterproof and transparent cellulose-based film is characterized by comprising the following preparation steps:

(1) Preparing the nano cellulose dispersion or the cellulose derivative solution into a transparent cellulose-based film by a high-molecular sol casting method or vacuum filtration;

(2) Soaking the transparent cellulose-based film in the step (1) in glacial acetic acid, and carrying out ion exchange reaction under the action of ultrasound; and cleaning the reacted cellulose-based film by using an organic solvent to obtain the water-resistant and transparent cellulose-based film.

2. A method of making a water-resistant, transparent cellulose-based film according to claim 1, wherein: the nano-cellulose in the step (1) is any one of nano-celluloses obtained by oxidizing or carboxymethylating wood fibers by TEMPO.

3. A method of making a water-resistant, transparent cellulose-based film according to claim 2, wherein: the wood fiber is any one of softwood pulp, hardwood pulp, non-wood pulp, waste paper pulp, fluff pulp and cotton pulp.

4. A method of making a water-resistant, transparent cellulose-based film according to claim 1, wherein: the cellulose derivative in the step (1) is sodium cellulose salt which can be dissolved in water.

5. The method of claim 1, wherein the cellulose derivative of step (1) has a molecular weight of 90000 ~ 700000.

6. The method for preparing a water-resistant transparent cellulose-based film according to claim 1, wherein the mass concentrations of the nanocellulose dispersion and the cellulose derivative solution in the step (1) are 0.5% ~ 2%.

7. The method for preparing a water-resistant transparent cellulose-based film according to claim 1, wherein the ion exchange time in step (2) is 2 ~ 4 hours and the ultrasonic power is 60 ~ 600W.

8. A method of making a water-resistant, transparent cellulose-based film according to claim 1, wherein: the organic solvent in the step (2) is any one of absolute ethyl alcohol and isopropanol.

9. A water-resistant, transparent cellulose-based film obtained by the production method according to any one of claims 1 to 8.

10. The water-resistant transparent cellulose-based film according to claim 9, wherein the cellulose-based film has a water absorption of 25 ~ 35%, an increase in thickness of 12 ~ 15%, an increase in length and width of 4 ~ 8%, a wet tensile strength of 15 ~ 30 MPa, and a light transmittance of 90 ~ 91% in the visible region after soaking in water for 24 ~ 72 hours.

Technical Field

The invention belongs to the technical field of papermaking, and particularly relates to a waterproof and transparent cellulose-based film and a preparation method thereof.

Background

The increasing energy crisis and environmental issues have forced scientists to find renewable materials to replace existing petroleum-based synthetic materials. Cellulose is the oldest and most abundant natural polymer on earth, cellulose products or cellulose derivatives with different properties can be obtained by processing the cellulose by mechanical, chemical, biological and other methods, and the transparent cellulose-based film prepared by the method has important application in the fields of food, energy, materials, chemical industry and the like. However, one of the major challenges faced in the practical application of cellulose-based films is their strong hydrophilic properties, which are severely impaired in the presence of moisture or water. [ Ben i z A J, Torres-Rendon J, Poutanen M, et al, Humidityand multiscale structure good mechanical properties and deformation modes of native cell nanofibers [ J ]. Biomacromolecules, 2013, 14(12): 4497) 4506 ]. Therefore, it is important in practical applications to improve the water resistance of transparent cellulose-based films.

At present, the method for improving the water resistance of the flexible transparent cellulose-based film mainly comprises the following steps: chemical modification, surface adsorption and crosslinking. For example, the water resistance of the nanopaper is improved by performing acetylation modification on the nanocellulose. Yagyu H, IfukuS, Nogi M. esterification of optical transmissive nanopaper for high-brightness and motion resistance in a Flexible device substrate [ J ]. Flexible and Printed Electronics, 2017, 2(1): 014003 ], but modifies cellulose molecules to make them hydrophobic and reduce the crystallinity of the fibers, thereby affecting the mechanical properties of the film. Compared with chemical modification using a large amount of chemical reagents, physical adsorption deposits a cationic hydrophobic substance on the surface of the fiber through simple electrostatic adsorption to form a hydrophobic layer, so that the cellulose film obtains good water resistance. Different kinds of alkyl quaternary ammonium salts are adsorbed on carboxyl groups on the surface of the nano-cellulose prepared by a TEMPO process, and a hydrophobic cellulose film is prepared by adopting a casting method. Although the adsorption effect of Shimizu M, Saito T, Fukuzumi H, et al, Hydrophobic, decrease, and transparentnocellulose filters with quaternary ammonium cations on the nano fibrous substrates [ J ]. Biomacromolecules, 2014, 15(11): 4320-4325 ] does not destroy the fiber structure, the introduction of the Hydrophobic surfactant may hinder the formation of hydrogen bonds between fibers, and the mechanical properties of the prepared film are poor. The method comprises the steps of mixing low-concentration polyamide epichlorohydrin (PAE) with nanocellulose to prepare a film, and then soaking the film in a PAE aqueous solution to enable a PAE cross-linking agent to be fully diffused into a cellulose film to generate a cross-linking effect, so that the film obtains high moisture resistance. [ Yang W, Bian H, Jiano L, et al, High wet-strand, thermal stable and transient TEMPO-oxidized cellulose nanofiber Membrane vision cross-linking with poly-amide ethylene glycol resin [ J ]. RSC Advances, 2017, 7(50): 31567. 31573.] High-valent metal ions are chemically cross-linked with cellulose fibers, [ Shimizu M, Saito T, Isoai A. Water-resin and High oxidative gene-bar cellulose resin resins with internal cellulose resin resins cross-linking with cellulose resin, 2015, 16(3): 1062-1071 ], can effectively improve the water resistance of the nano cellulose membrane, but the crosslinking process is complex and time-consuming.

The invention takes nano-cellulose or cellulose and derivatives thereof as raw materials, and prepares the transparent cellulose-based film by macromolecular sol casting or vacuum filtration. On the basis, the dried film is immersed in glacial acetic acid and is subjected to ultrasonic treatment; finally, the film is cleaned in an organic solvent to obtain a waterproof and transparent cellulose-based film. The water-resistant treatment process is simple, and the excellent transparency of the film is reserved.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art and provides a waterproof and transparent cellulose-based film and a preparation method thereof.

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

A water-resistant, transparent cellulose-based film and a method of making the same, the method comprising the steps of:

(1) Preparing the nano cellulose dispersion or the cellulose derivative solution into a transparent cellulose-based film by a high-molecular sol casting method or vacuum filtration;

(2) Then, soaking the transparent cellulose-based film in the step (1) in pure glacial acetic acid, and carrying out ion exchange reaction under the action of ultrasound; and then washing the cellulose-based film after reaction by using an organic solvent to obtain the water-resistant and transparent cellulose-based film.

Further preferably, the nanocellulose in the step (1) is any one of nanocelluloses obtained by performing TEMPO oxidation or carboxymethylation pretreatment on the wood fibers.

Further preferably, the wood fiber for preparing the nanocellulose in the step (1) is any one of softwood pulp, hardwood pulp, non-wood pulp, waste paper pulp, fluff pulp and cotton pulp.

Further preferably, the mass concentration of the nanocellulose dispersion in step (1) is 0.5 ~ 2%.

Further preferably, the cellulose derivative in step (1) is a water-soluble sodium cellulose salt, such as sodium carboxymethyl cellulose.

Further preferably, the molecular weight of the cellulose derivative in step (1) is 90000 ~ 700000.

Further preferably, the mass concentration of the cellulose derivative solution in the step (1) is 0.5% ~ 2%.

Further preferably, the time of ion exchange in step (2) is 2 ~ 4 h.

Further preferably, the ultrasonic power of the ultrasound in the step (2) is 60 ~ 600W.

Further preferably, the organic solvent used in step (2) is any one of absolute ethanol and isopropyl alcohol.

The water-resistant transparent cellulose-based film prepared by the preparation method is soaked in water for 24 ~ 72 h, the water absorption rate is 25 ~ 35%, the thickness is increased by 12 ~ 15%, the length and the width are increased by 4 ~ 8%, the wet tensile strength is 15 ~ 30 MPa, and the light transmittance in a visible light region is 90 ~ 91%.

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

(1) The invention provides a waterproof and transparent cellulose-based film and a preparation method thereof, and the preparation process is simple;

(2) The invention provides a waterproof and transparent cellulose-based film and a preparation method thereof, which do not relate to the addition of chemicals, and the organic solvent for ion replacement has recyclability;

(2) the invention provides a waterproof and transparent cellulose-based film and a preparation method thereof, and the film keeps higher light transmittance.

Detailed Description

The invention is further described with reference to specific examples, but the scope of the invention is not limited to the examples.

In the following examples, water absorption and dimensional stability were measured by ASTM D570-98; the transparency of the cellulose film is determined according to the national standard GB/T2410-2008.