阅读说明：本技术 一种用于食品包装纸的含氟疏水抗油改性纳米纤维素及其制备方法 (Fluorine-containing hydrophobic oil-resistant modified nano-cellulose for food packaging paper and preparation method thereof ) 是由 赵新民 邱旭峰 杨柳青 林俊辉 刘敏 陈宪 于 2019-11-05 设计创作，主要内容包括：本发明公开了一种用于食品包装纸的含氟疏水抗油改性纳米纤维素及其制备方法,属于功能材料技术领域。本发明先将氧化纳米纤维素稀释成浓度为1-1.5％的纳米纤维素水悬浮液后蒸发,获得凝胶状纳米纤维素,然后依次用三氟醋酸酐、2,2-二氟乙胺对所述纳米纤维素进行改性,获得含氟疏水抗油改性纳米纤维素。本发明经含氟疏水抗油改性后的纳米纤维素具备良好的抗水性和成膜性,将其涂敷于食品包装纸表面后,可形成均匀的膜层,有效阻隔水蒸汽和氧气的渗透,从而延长食品的保质期；另外由于纳米纤维素具有很大的比表面积和丰富的羟基,可与纤维紧密结合,从而提高纤维间结合力和纸张的强度,提高食品包装纸使用的可靠性。(The invention discloses fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper and a preparation method thereof, and belongs to the technical field of functional materials. The method comprises the steps of diluting oxidized nano-cellulose into nano-cellulose water suspension with the concentration of 1-1.5%, evaporating to obtain gel-like nano-cellulose, and modifying the nano-cellulose by trifluoroacetic anhydride and 2, 2-difluoroethylamine in sequence to obtain the fluorine-containing hydrophobic oil-resistant modified nano-cellulose. The nano-cellulose modified by fluorine-containing hydrophobic oil-resistant has good water resistance and film-forming property, and can form a uniform film layer after being coated on the surface of food packaging paper, so that the permeation of water vapor and oxygen can be effectively prevented, and the shelf life of food is prolonged; in addition, because the nano-cellulose has large specific surface area and abundant hydroxyl groups, the nano-cellulose can be tightly combined with fibers, so that the binding force among the fibers and the strength of paper are improved, and the use reliability of food packaging paper is improved.)

1. A preparation method of fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper is characterized by comprising the following steps: the method specifically comprises the following steps:

(1) diluting oxidized nano-cellulose into nano-cellulose water suspension with the concentration of 1-1.5%, and evaporating to obtain gel-like nano-cellulose; then uniformly mixing the gel-like nano cellulose with a dispersing agent N-N-dimethylformamide, and continuously stirring for 3-6h at a constant temperature of 85-90 ℃; adding trifluoroacetic anhydride and 4-dimethylaminopyridine into the reaction system, stirring and dispersing uniformly, heating to 100 ℃, continuing to react for 3-6h, cooling, and washing the product to obtain esterified modified nanocellulose;

(2) adding a 2, 2-difluoroethylamine solution into the esterified modified nanocellulose obtained in the step (1) according to a ratio, uniformly mixing to obtain a mixed reaction solution, adjusting the pH value of the reaction solution to be neutral, and stirring and reacting at a constant temperature of 60-70 ℃ for 4-6 hours; and after the reaction is finished, centrifuging and washing the product, and finally performing dialysis treatment to obtain the fluorine-containing hydrophobic oil-resistant modified nano-cellulose.

2. The preparation method of the fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper according to claim 1, characterized in that: the oxidized nano-cellulose in the step (1) is prepared by processing fiber slurry by a TEMPO oxidation-mechanical method.

3. The preparation method of the fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper according to claim 1, characterized in that: the mass ratio of the nano-cellulose to trifluoroacetic anhydride to 4-dimethylaminopyridine in the step (1) is 1: 30-50: 0.5-2.0.

4. The preparation method of the fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper according to claim 1, characterized in that: the concentration of the 2, 2-difluoroethylamine solution in the step (2) is 2-5%.

5. The preparation method of the fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper according to claim 1, characterized in that: the mass ratio of the esterified modified nano-cellulose to 2, 2-difluoroethylamine in the step (2) is 1: 0.3-0.6.

6. The fluorine-containing hydrophobic oil-resistant modified nanocellulose prepared by the method for preparing fluorine-containing hydrophobic oil-resistant modified nanocellulose according to any one of claims 1 to 5.

7. Use of the fluorine-containing hydrophobic oil-resistant modified nanocellulose prepared by the method of any one of claims 1 to 5 in food packaging paper.

Technical Field

The invention belongs to the technical field of functional materials, and particularly relates to fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper and a preparation method thereof.

Background

With the improvement of environmental protection consciousness and the promulgation of national plastic banning orders, plastic is no longer used as a packaging material in many areas, but recyclable, degradable and white pollution-free paper is used instead. However, the food wrapping paper has the disadvantages of poor oxygen resistance and water vapor resistance under the condition of high environmental humidity, so that the using effect and the safety of the packaged food are affected, and the adoption of waxing or film coating also has safety risks. Therefore, the invention aims at the problem and develops a novel hydrophobic modified nano cellulose composite emulsion as a surface sizing agent to improve the environmental adaptability of food packaging paper and simultaneously improve the oil resistance of the food packaging paper.

The technical problems to be solved by the invention are as follows:

1. safety problem of food packaging paper

The general food wrapping paper is usually coated with wax or sprayed on the surface of paper to improve the water and oil resistance of the paper. However, whether the surface of the food packaging paper is waxed or coated with the film is safe is also a concern of government, public and technical personnel in related fields, and certain potential safety hazards exist for the surface of the food packaging paper to be waxed or coated with the film; for example, wax coated paper is used for containing hot water, which can melt paraffin on the inner wall of the paper cup and possibly harm the health. In addition, the wax and the polymer film bring troubles in the process of recycling waste paper, and the waste paper pulp is difficult to be processed cleanly, thereby affecting the environmental sanitation and the environmental safety.

2. The strength and the obstruction of food packaging paper

Under the condition of high environmental humidity, water vapor of common food packaging paper can easily permeate into paper pores, and the water absorption of the paper is high, so that the physical strength of the paper is obviously reduced, the paper is easy to break, and the food packaged by the paper can be damaged; in addition, the oxygen and water vapor blocking capability of the food packaging paper is weakened, so that the packaged food is easy to deteriorate and difficult to meet the high requirements of food packaging.

For the above reasons, the present application has been made.

Disclosure of Invention

In view of the problems or defects of the prior art, the invention aims to provide fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper and a preparation method thereof. The invention adopts fluorine-containing modified nano-cellulose to replace paraffin or laminating film to carry out surface sizing on the food packaging base paper. The nano-cellulose has the advantages of biodegradability, wide source, safety, environmental protection and the like, and the modified nano-cellulose is safe, reliable, waterproof and oilproof; therefore, the method has great development prospect when being applied to food packaging paper.

In order to achieve one of the above objects of the present invention, the present invention adopts the following technical solutions:

a preparation method of fluorine-containing hydrophobic oil-resistant modified nanocellulose for food packaging paper specifically comprises the following steps:

(1) diluting oxidized nano-cellulose into nano-cellulose water suspension with the concentration of 1-1.5%, and evaporating to obtain gel-like nano-cellulose; then uniformly mixing the gel-like nano cellulose with a dispersing agent N-N-dimethylformamide, and continuously stirring for 3-6h at a constant temperature of 85-90 ℃; adding trifluoroacetic anhydride and 4-dimethylaminopyridine into the reaction system, stirring and dispersing uniformly, heating to 100 ℃, continuing to react for 3-6h, cooling, and washing the product to obtain esterified modified nanocellulose;

(2) adding a 2, 2-difluoroethylamine solution into the esterified modified nanocellulose obtained in the step (1) according to a ratio, uniformly mixing to obtain a mixed reaction solution, adjusting the pH value of the reaction solution to be neutral, and stirring and reacting at a constant temperature of 60-70 ℃ for 4-6 hours; and after the reaction is finished, centrifuging and washing the product, and finally performing dialysis treatment to obtain the fluorine-containing hydrophobic oil-resistant modified nano-cellulose.

Further, in the above technical solution, the oxidized nanocellulose (ToCN) in step (1) is prepared by processing a fiber slurry by a TEMPO oxidation-mechanical method.

Further, according to the technical scheme, the mass ratio of the nano-cellulose to trifluoroacetic anhydride to 4-dimethylaminopyridine in the step (1) is 1: 30-50: 0.5-2.0.

Further, in the above technical scheme, the concentration of the 2, 2-difluoroethylamine solution in the step (2) is 2-5%, and the specific preparation method of the 2, 2-difluoroethylamine solution is as follows: adding 2-5g of 2, 2-difluoroethylamine into 100mL of N-N Dimethylformamide (DMF), and uniformly stirring.

Further, in the technical scheme, the mass ratio of the esterified modified nanocellulose in the step (2) to 2, 2-difluoroethylamine is 1: 0.3-0.6.

Further, in the above technical scheme, the constant temperature stirring reaction in the step (2) is specifically a constant temperature reaction under the stirring speed condition of 500-600 rpm.

The second purpose of the invention is to provide the fluorine-containing hydrophobic oil-resistant modified nano-cellulose for food packaging paper prepared by the method.

The third purpose of the invention is to provide the application of the fluorine-containing hydrophobic oil-resistant modified nano-cellulose prepared by the method in food packaging paper.

Compared with the prior art, the fluorine-containing hydrophobic oil-resistant modified nano-cellulose for the food packaging paper and the preparation method thereof have the following beneficial effects:

(1) for the problems of strength and barrier property of food packaging, the invention adopts fluorine-containing hydrophobic modified nano-cellulose and compounds chitosan and polylactic acid (PLA) to be applied to food packaging paper. The fluorine-containing hydrophobically modified nano-cellulose has good water resistance and film forming property, and can form a uniform film layer after being coated on the surface of food packaging paper, thereby effectively blocking the permeation of water vapor and oxygen and further prolonging the shelf life of food; in addition, because the nano-cellulose has large specific surface area and rich hydroxyl groups, the nano-cellulose can be tightly combined with fibers, so that the binding force among the fibers and the strength of paper are improved, and the use reliability of food packaging paper is improved; in addition, the added chitosan and polylactic acid (PLA) can also improve the physical property and antibacterial property of paper, and the chitosan and the PLA are compounded to apply glue on the surface of the paper, so that the oxygen and water vapor barrier property and the physical strength property of the food packaging paper under the condition of high environmental humidity can be improved.

(2) For the safety problem of food packaging paper, the invention adopts fluorine-containing modified nano-cellulose to replace paraffin or a drench film to carry out surface sizing on the food packaging paper. The nano-cellulose has the advantages of biodegradability, wide source, safety, environmental protection and the like, and the modified nano-cellulose is safe, reliable, waterproof and oilproof; therefore, the method has great development prospect when being applied to food packaging paper.

Drawings

FIG. 1 is a process flow diagram of the present invention for preparing fluorine-containing hydrophobic oil-resistant modified nanocellulose;

FIG. 2 is a process flow chart of preparing food wrapping paper by using the fluorine-containing hydrophobic oil-resistant modified nano-cellulose of the invention.

Detailed Description

The present invention will be described in further detail below with reference to examples. The present invention is implemented on the premise of the technology of the present invention, and the detailed embodiments and specific procedures are given to illustrate the inventive aspects of the present invention, but the scope of the present invention is not limited to the following embodiments.

Various modifications to the precise description of the invention will be readily apparent to those skilled in the art from the information contained herein without departing from the spirit and scope of the appended claims. It is to be understood that the scope of the invention is not limited to the procedures, properties, or components defined, as these embodiments, as well as others described, are intended to be merely illustrative of particular aspects of the invention. Indeed, various modifications of the embodiments of the invention which are obvious to those skilled in the art or related fields are intended to be covered by the scope of the appended claims.

For a better understanding of the invention, and not as a limitation on the scope thereof, all numbers expressing quantities, percentages, and other numerical values used in this application are to be understood as being modified in all instances by the term "about". Accordingly, unless expressly indicated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The three key properties of the food wrapping paper developed in the present invention are oxygen barrier, water vapor barrier and physical strength properties. The invention designs a novel method, trifluoroacetic anhydride is used as a reagent for esterifying and modifying the nano-cellulose, and the reagent and hydroxyl groups on the nano-cellulose are subjected to esterification reaction, so that the hydrophobicity is obviously improved; 2, 2-difluoroethylamine reacts with the esterification modified nanocellulose through electrostatic adsorption to form a complex, so that the hydrophobicity is further improved. Because the adopted fluorine-containing modifier is adopted, the oil resistance of the product is improved. The food packaging paper with the surface glued by the nano-cellulose can be used in a humid environment. The effect of the invention is mainly influenced by the concentration of the modified nano-cellulose; the higher the concentration is, the better the oxygen and water vapor resistance is, and the better the strength performance is; but the influence of cost is also considered, so that proper concentration needs to be selected to be compounded with chitosan and PLA for surface sizing, and the oil-proof performance and the antibacterial performance of the food packaging paper can be improved by adopting the chitosan.

The nano-cellulose adopted in the invention is derived from plant fiber raw materials, and has the advantages of safety, environmental protection, degradability and the like.

The concentration of each reagent of the present invention refers to the mass/volume percent concentration of the dispersoid and the dispersion medium in g/mL.