Hydrophobic cellulose and hydrophobic modification method thereof

Abstract

The invention belongs to the technical field of cellulose preparation, and particularly relates to hydrophobic cellulose and a hydrophobic modification method thereof. In order to solve the problems that an existing cellulose hydrophobic modification method is complex, and chemical reagents are not environmentally friendly, the invention provides a cellulose hydrophobic modification method which comprises the following steps: adding cellulose into a mixed acid modifier for esterification reaction, and then washing with water, the ratio of the cellulose to the mixed acid is (30-100): 1 g / L; the mixed acid system is prepared from 15 to 25 weight percent of HNO3, 35 to 50 weight percent of H2SO4 and 30 to 40 weight percent of water. Water-proof and oil-proof test results show that the water-proof and oil-proof effects of the modified cellulose can reach higher levels, so that the modified cellulose has a better hydrophobic effect. Therefore, the hydrophobic cellulose obtained by the modification method has potential commercial value in replacing plastic packaging and disposable environment-friendly products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cellulose preparation, and particularly relates to a hydrophobic cellulose and a hydrophobic modification method thereof. BACKGROUND

[0002] As a natural polymer compound, cellulose has the advantages of being renewable, biodegradable, and reducing carbon footprint, and can replace plastic packaging and disposable environmentally friendly products. However, cellulose is difficult to effectively block water, oil and gas due to a large number of hydrophilic groups-hydroxyl groups, which is a key bottleneck for cellulose-based packaging materials to replace disposable plastics. Therefore, cellulose is hydrophobically modified to expand the application range of cellulose products in the packaging field while maintaining the advantages of biodegradability, low cost and large-scale production of cellulose. Current methods for hydrophobic modification of cellulose include chemical modification, physical blending and surface coating. Chemical modification is the most durable and stable modification method, which covalently bonds hydrophobic groups to the cellulose molecular chain. For example, patent CN119954975A discloses a preparation method of modified hydroxyethyl cellulose and its application in coatings. The cellulose is subjected to alkalization, etherification and modifier modification steps to obtain hydrophobic groups. However, the modification steps are complex and not conducive to actual operation, and involve harmful substances such as dimethyl sulfoxide, which is not environmentally friendly. Therefore, it is urgent to develop a simpler and more convenient method for modifying cellulose to obtain hydrophobic cellulose. SUMMARY

[0003] In order to overcome the problems of complex cellulose hydrophobic modification method and non-environmentally friendly chemical reagents, the present application provides a new method for modifying the hydrophobicity of cellulose.

[0004] To achieve the above application purposes, the technical solutions adopted by the present application are as follows: In a first aspect, the present application provides a method for modifying the hydrophobicity of cellulose, comprising the following steps: adding cellulose to a mixed acid modifier for esterification, and then washing with water; the cellulose to mixed acid ratio is 30-100:1 g / L; the mixed acid system is composed of 15-25 wt% HNO3, 35-50 wt% H2SO4 and 30-40 wt% water.

[0005] In the esterification reaction, the reaction temperature is 40-50℃.

[0006] In the esterification reaction, the reaction time is 30-80 min.

[0007] The washing of the modified cellulose is performed to a pH of 6.0-7.0.

[0008] The esterification reaction process is that the nitric acid group substitution degree DS≤1.0.

[0009] The cellulose is selected from at least one of plant pulp or refined cotton.

[0010] In a second aspect, the present application provides the hydrophobic cellulose prepared by the above hydrophobic modification method.

[0011] Beneficial effects: The present application uses a high-moisture nitro-sulfur mixed acid system as a cellulose modifier. The cellulose and the nitro-sulfur mixed acid system undergo an esterification reaction to generate hydrophobic cellulose with a total nitric acid group substitution degree DS≤1.0. The waterproof and oil-proof test results show that the modified cellulose of the present application can achieve high waterproof and oil-proof effects. Moreover, the modification treatment method used in the present application is low in cost and simple in operation. The hydrophobicity of the product can be adjusted by adjusting the content of nitric acid and sulfuric acid in the modifier, and the method is suitable for modifying cellulose of different sources. Therefore, the hydrophobic cellulose obtained by the modification method of the present application has potential commercial value in replacing plastic packaging and disposable environmentally friendly products. DETAILED DESCRIPTION

[0012] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail in combination with embodiments. Unless otherwise defined, all technical terms used in the present application have the same meanings as understood by those skilled in the art.

[0013] The solutions of the present application will be explained by specific examples below. Those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or according to the product instructions are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0014] Example 1 A 2 L mixed acid modifier was prepared, which consisted of 25 wt% HNO3, 45 wt% H2SO4 and 30 wt% H2O. The mixed acid modifier was poured into a reactor and heated to 50 ℃. Then, 150 g of wood pulp was added to the reactor. After reacting for 60 min under the condition of a 50 ℃ water bath, the product was washed with water multiple times until the pH value was 6.8, thereby obtaining the modified cellulose.

[0015] Example 2 A 2 L mixed acid modifier was prepared with the components of 15 wt% HNO3, 45 wt% H2SO4, and 40 wt% H2O. The mixed acid modifier was poured into the reactor and heated to 40 °C. 100 g of refined cotton was added to the reactor. After 30 min of reaction in a 40 °C water bath, the product was washed with water multiple times until the pH value was 6.5. Thus, the modified hydrophobic cellulose was prepared.

[0016] Example 3 A 2 L mixed acid modifier was prepared with the components of 20 wt% HNO3, 40 wt% H2SO4, and 40 wt% H2O. The mixed acid modifier was poured into the reactor and heated to 50 °C. 150 g of bamboo pulp was added to the reactor. After 80 min of reaction in a 40 °C water bath, the product was washed with water multiple times until the pH value was 6.5. Thus, the modified cellulose was prepared.

[0017] Comparative Example 1 Compared with Example 1, the difference was that the components of the mixed acid modifier were 10 wt% HNO3, 60 wt% H2SO4, and 30 wt% H2O, and the rest of the operations were the same as those of Example 1.

[0018] Water and oil repellency test The following method was used for evaluation: 2% aqueous suspensions of unmodified cellulose and 2% suspensions of modified cellulose obtained by Example 1, Example 2, and Example 3 of the present application (ethanol: nonafluorobutylether = 8:2) were coated on the surface of the base paper at a coating amount of 1 wt%. The water repellency grade was then tested by the water drop test method, in which a mixture of water and isopropyl alcohol at different ratios (as shown in Table 1) was dropped onto the surface of the paper with a dropper. If the paper was not wetted within 5 s, it passed the water repellency grade. The water repellency grade was 0-3, and the higher the grade, the better the water repellency. The oil repellency grade was tested according to GB / T 19977-2005, and the oil repellency grade was 1-7, and the higher the grade, the better the oil repellency. The results are shown in Table 2.

[0019] Table 1 Different ratios of water and isopropyl alcohol

[0020] Table 2 Water and oil repellency test results of different experimental groups of cellulose

Claims

1. A method for hydrophobic modification of cellulose, characterized in that, Includes the following steps: Cellulose is added to a mixed acid modifier for esterification, followed by washing with water; the ratio of cellulose to mixed acid is 30-100:1 g / L; the mixed acid system consists of 15-25 wt% HNO3, 35-50 wt% H2SO4 and 30-40 wt% water.

2. The method for hydrophobic modification of cellulose according to claim 1, characterized in that, The reaction temperature in the esterification reaction is 40–50 °C.

3. The method for hydrophobic modification of cellulose according to claim 1, characterized in that, The reaction time in the esterification reaction is 30 to 80 minutes.

4. The method for hydrophobic modification of cellulose according to claim 1, characterized in that, The water washing involves washing the modified cellulose with water until the pH reaches 6.0–7.

0.

5. The method for hydrophobic modification of cellulose according to claim 1, characterized in that, During the esterification reaction, the degree of substitution of the nitrate group DS ≤ 1.

0.

6. The method for hydrophobic modification of cellulose according to any one of claims 1 to 5, characterized in that, The cellulose is selected from at least one of plant pulp or refined cotton.

7. Hydrophobic cellulose prepared by the hydrophobic modification method according to any one of claims 1 to 6.

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