Super water-resistant paper and its preparation method

Abstract

The application discloses super-strong water-resistant paper and a preparation method thereof. The super-strong water-resistant paper comprises twisted and intertwined microfibers and in-situ regenerated nanofibers. The twisted and intertwined structure of the microfibers will not lose strength due to opening of hydrogen bonds, and the in-situ regenerated nanofibers form a dense film structure to tightly wrap the connection of the microfibers. The preparation method of the water-resistant paper comprises the following steps: treating cellulose paper with concentrated alkali, so that the fibers change from a flat lapping structure to a twisted and intertwined structure, are locked with each other, and the interaction is obviously improved; further, small fibers on the surface of the fibers are dissolved and regenerated in situ, so that the overall combination sites of the fibers are obviously increased, and the interaction is further enhanced. The application solves the problem of how to make the paper keep excellent water resistance without adding any other materials. Based on the adhesion of the twisted and intertwined fibers and the regenerated fibers, the wet strength of the paper is greatly improved, and the application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of water-resistant paper and its preparation method, more particularly to a kind of super water-resistant paper and its preparation method. BACKGROUND

[0002] Under the current social environment, plastic pollution and plastic crisis have become a global hot topic of concern. The massive use of plastic products leads to environmental pollution, ecological destruction and health risks, and an environmentally friendly material that can replace plastic is urgently needed. Paper, as a degradable and environmentally friendly material, has great potential to replace plastic, but its poor water resistance limits its application and development. If the water resistance of paper can be improved so that it can work in water for a long time and maintain good strength, it can be applied to more fields, which is a problem to be solved at present.

[0003] A large number of studies have been conducted to address this issue. Mainly including introducing hydrophobic additives during paper preparation or coating waterproof agents on the surface after paper preparation to enhance the water resistance of paper. In addition, by modifying, regenerating, crosslinking and other methods of fibers, the stability of fibers in water environment can also be improved, further strengthening the performance of super water-resistant paper.

[0004] However, the existing water-resistant paper preparation method has some challenges, such as complex process, high production cost, and environmental problems, which limit the application and promotion of super water-resistant paper. Therefore, it is of great research significance to study innovative solutions to these challenges and develop paper materials with excellent water resistance. SUMMARY

[0005] The present application aims to provide a super water-resistant paper with excellent water resistance, and also aims to provide a preparation method of the super water-resistant paper.

[0006] Technical solution: The super water-resistant paper according to the present application is a dense structure composed of twisted and tangled microfibers and in-situ regenerated fibers. The twisted and tangled structure of the microfibers will not lose strength due to the opening of hydrogen bonds, and the in-situ regenerated nanofibers fill the microfibers and make them closely connected. The dense membrane structure formed by the regenerated nanofibers tightly wraps the connection between the microfibers, effectively blocking the penetration of water and further improving the water resistance of the paper.

[0007] Preferably, the thickness of the super water-resistant paper is 50-200 μm; the density is 1.0-1.4 g·cm -3 .

[0008] Preferably, the wet tensile strength of the super water-resistant paper can reach 2.85-9.5 KN / m, the dry tensile strength can reach 7.6-11.4 KN / m, and the wet strength retention rate is 25%-83%.

[0009] The preparation method of the super water-resistant paper comprises the following steps:

[0010] The cellulose paper is immersed in an A treatment solution, alkali treated and washed to obtain a first intermediate; the A treatment solution is one or more of a sodium hydroxide solution, a calcium hydroxide solution and a potassium hydroxide solution;

[0011] The first intermediate is immersed in a B treatment solution to dissolve part of the fibers to obtain a second intermediate; the B treatment solution is one of an alkali / urea mixed solution, a lithium chloride / N.N dimethylacetamide solution, an N-methyl morpholine-N-oxide solution, an ion solution and a copper ammonia solution;

[0012] The second intermediate is washed and dried to obtain the super water-resistant paper.

[0013] During the concentrated alkali treatment process, the hydrated ion dipole compound formed penetrates into the amorphous region and the crystalline region inside the cellulose fiber, forms hydrogen bonds with the cellulose molecules, changes the crystal structure, destroys the cell wall of the plant cell, causes the expansion, shrinkage and torsion of the fiber. Further, the fine fiber part on the surface of the fiber is dissolved and regenerated in situ, greatly increases the binding sites, so that the fibers can be tightly combined even without being twisted and tangled, further enhances the interaction between the fibers and improves the water resistance of the paper.

[0014] Preferably, the cellulose source in the cellulose paper includes but is not limited to woody plants, liana plants or herbaceous plants.

[0015] Preferably, the concentration of the A treatment solution is 1% to 20%, and the treatment temperature is 0 to 60°C.

[0016] Preferably, the mass ratio of the absolutely dry cellulose paper to the A treatment solution is 1 to 5:30, and the treatment method of the A treatment solution comprises soaking in the A treatment solution at 0 to 60°C for 10 minutes to 5 hours, and washing after the treatment is completed. This step uses concentrated alkali to treat the cellulose paper, so that the fibers change from a flat lapping structure to a twisted and tangled structure, and are locked with each other.

[0017] Preferably, the temperature for the B treatment solution to be treated is -20 to 170°C, and the treatment time is 5 minutes to 5 hours.

[0018] Preferably, the second intermediate obtained after the B treatment solution treatment needs to be placed for 1 to 30 minutes.

[0019] Preferably, the drying method includes but is not limited to air drying at room temperature, oven drying and hot-press drying and various other methods, and the drying temperature is 20 to 120°C.

[0020] Preferably, in the washing process of the sample in step (3), the addition of the washing reagent destroys the dissolving system of the fibers, and the fibers are regenerated.

[0021] Advantages: Compared with the prior art, the present application has the following remarkable advantages: the water-resistant paper has high paper wet strength, and the two-step treatment of cellulose by the A solution and the B solution has a synergistic effect on the improvement of paper wet strength and water resistance, and the dense membrane structure of the regenerated nanofibers in the obtained water-resistant paper tightly wraps the micron-sized fiber junctions, effectively blocks the penetration of water, and improves the water resistance of the paper. The present application solves the problem of how to make the paper maintain excellent water resistance without adding any other materials. Based on the adhesion of twisted and entangled fibers and regenerated fibers, the wet strength of the paper is greatly improved, and the present application has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A scanning electron microscope cross-sectional morphology of the twisted and entangled fibers of the super-strong water-resistant paper prepared in Example 1 is fully filled with regenerated cellulose;

[0023] Figure 2 A SEM image of the base paper;

[0024] Figure 3 A SEM image of the water-resistant paper prepared in Comparative Example 1;

[0025] Figure 4 A SEM image of the water-resistant paper prepared in Comparative Example 2;

[0026] Figure 5 A wet tensile strength diagram of the base paper, the water-resistant paper prepared in Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be further described below in combination with the drawings.

[0028] Example 1

[0029] As shown in the drawings, Figure 1 a super-strong water-resistant paper and a preparation method thereof, the super-strong water-resistant paper comprising twisted and entangled micron fibers and in-situ regenerated nanofibers. The twisted and entangled structure of the micron fibers will not lose strength due to the opening of hydrogen bonds, and the in-situ regenerated nanofibers fill the micron fibers and tightly connect them.

[0030] The preparation method of the above-mentioned super-strong water-resistant paper is as follows:

[0031] (1) The lignin, hemicellulose and the like in the wood are removed, cellulose is extracted and prepared into cellulose paper. The cellulose paper is immersed in 18% sodium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the sodium hydroxide solution is 1:30, heated at 50°C for 30 min, and washed with clean water to obtain a first intermediate;

[0032] (2) The above partially lignin-removed bamboo is immersed in N.N dimethylacetamide solution, placed in an environment at 160°C for sufficient reaction for 20 min, then cooled to 105°C, and lithium chloride is added for heat treatment for 30 min, the mass ratio of the lithium chloride to the N.N dimethylacetamide solution is 1:10, and static for 10 min to obtain a second intermediate;

[0033] (3) The second intermediate is washed with anhydrous ethanol, and placed in a hot press at 60°C and 20 MPa until completely dried.

[0034] The obtained super-strong water-resistant paper has a thickness of 50 μm, a dry tensile strength of 11.4 KN / m, a wet tensile strength of 6.5 KN / m, and a wet strength retention rate of 58.3%.

[0035] Example 2

[0036] (1) The lignin, hemicellulose and the like in the wood are removed, cellulose is extracted and prepared into cellulose paper. The cellulose paper is immersed in 10% calcium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the calcium hydroxide solution is 2:30, heated at 30°C for 5 h, and washed with clean water to obtain a first intermediate;

[0037] (2) The first intermediate is immersed in copper ammonia solution, and placed in an environment at 80°C for sufficient reaction for 2 h to obtain a second intermediate;

[0038] (3) The second intermediate is washed with anhydrous ethanol and dried to obtain a super-strong water-resistant paper.

[0039] The obtained super-strong water-resistant paper has a thickness of 120 μm, a dry tensile strength of 8.55 KN / m, a wet tensile strength of 3.325 KN / m, and a wet strength retention rate of 38.8%.

[0040] Example 3

[0041] (1) The lignin, hemicellulose and the like in the wood are removed, cellulose is extracted and prepared into cellulose paper. The cellulose paper is immersed in 10% calcium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the calcium hydroxide solution is 2:30, heated at 30°C for 5 h, and washed with clean water to obtain a first intermediate;

[0042] (2) The first intermediate is immersed in an alkali / urea mixed solution, and placed in an environment at -20°C for sufficient reaction for 4 h to obtain a second intermediate;

[0043] (3) The second intermediate is washed with clean water and placed in a 90°C, 10MPa hot press until completely dry.

[0044] The thickness of the obtained super-strong water-resistant paper is 70μm, the dry tensile strength can reach 10.45KN / m, the wet tensile strength can reach 5.23KN / m, and the wet strength retention rate is 50%.

[0045] Example 4

[0046] (1) The lignin, hemicellulose and the like in the vine plant are removed, and cellulose is extracted and prepared into cellulose paper. The cellulose paper is immersed in a 10% potassium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the potassium hydroxide solution is 4:30, heated at 30°C for 30 min, and washed with clean water to obtain a first intermediate;

[0047] (2) The first intermediate is immersed in an N.N dimethylacetamide solution, placed in an environment of 160°C for 5 min, then cooled to 105°C, and lithium chloride is added for heat treatment for 2 h, the mass ratio of lithium chloride to N.N dimethylacetamide solution is 1:10, and static for 30 min to obtain a second intermediate;

[0048] (3) The second intermediate is washed with clean water and placed in a 30°C, 20MPa hot press until completely dry.

[0049] The thickness of the obtained super-strong water-resistant paper is 55μm, the dry tensile strength can reach 10.93KN / m, the wet tensile strength can reach 5.7KN / m, and the wet strength retention rate is 52.2%.

[0050] Example 5

[0051] (1) The lignin, hemicellulose and the like in the herbaceous plant are removed, and cellulose is extracted and prepared into cellulose paper. The cellulose paper is immersed in a 5% sodium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the sodium hydroxide solution is 5:30, heated at 20°C for 5 h, and washed with clean water to obtain a first intermediate;

[0052] (2) The first intermediate is immersed in an N.N dimethylacetamide solution, placed in an environment of 160°C for 1 h, then cooled to 105°C, and lithium chloride is added for heat treatment for 10 min, the mass ratio of lithium chloride to N.N dimethylacetamide solution is 1:10, and static for 5 min to obtain a second intermediate;

[0053] (3) The second intermediate is washed with clean water and placed in a 90°C oven until completely dry.

[0054] The thickness of the obtained super-strong water-resistant paper is 200μm, the dry tensile strength can reach 7.6KN / m, the wet tensile strength can reach 2.85KN / m, and the wet strength retention rate is 47.5%.

[0055] Example 6

[0056] (1) The lignin, hemicellulose and the like in the herbaceous plant were removed, and cellulose was extracted and prepared into cellulose paper. The cellulose paper was immersed in a 20% calcium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the calcium hydroxide solution was 1:30, and the cellulose paper was heated at 60°C for 30 min, and then washed with clean water to obtain a first intermediate;

[0057] (2) The first intermediate was immersed in a copper ammonia solution, and was fully reacted in a 60°C environment for 4 h to obtain a second intermediate;

[0058] (3) The second intermediate was washed with anhydrous ethanol, and was placed in a 40°C oven until completely dried.

[0059] The obtained super strong water-resistant paper had a thickness of 200 μm, a dry tensile strength of 7.6 KN / m, a wet tensile strength of 7.6-3.8 KN / m, and a wet strength retention rate of 50%.

[0060] Example 7

[0061] (1) The lignin, hemicellulose and the like in the herbaceous plant were removed, and cellulose was extracted and prepared into cellulose paper. The cellulose paper was immersed in a 20% calcium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the calcium hydroxide solution was 1:30, and the cellulose paper was heated at 60°C for 30 min, and then washed with clean water to obtain a first intermediate;

[0062] (2) The first intermediate was immersed in an alkali / urea mixed solution, and was fully reacted in a -5°C environment for 5 h to obtain a second intermediate;

[0063] (3) The second intermediate was washed with clean water, and was placed in a 30°C oven until completely dried.

[0064] The obtained super strong water-resistant paper had a thickness of 200 μm, a dry tensile strength of 5.7 KN / m, a wet tensile strength of 2.8-5 KN / m, and a wet strength retention rate of 50%.

[0065] Comparative Example 1

[0066] The lignin, hemicellulose and the like in the wood were removed, and cellulose was extracted and prepared into cellulose paper. The cellulose paper was immersed in an 18% sodium hydroxide solution, the mass ratio of the absolute dry mass of the cellulose paper to the mass of the sodium hydroxide solution was 1:30, and the cellulose paper was heated at 50°C for 30 min, and then washed with clean water to obtain the comparative example 1 paper, which was washed with anhydrous ethanol, and was placed in a 60°C, 20 MPa hot press until completely dried.

[0067] The SEM image of the obtained comparative example 1 water-resistant paper is shown in Figure 3Its thickness is 50μm, and its dry tensile strength can reach 3.37KN / m, wet tensile strength can reach 0.71KN / m, and wet strength retention rate is 21.07%.

[0068] Comparative Example 2

[0069] (2) Remove lignin, hemicellulose, etc. from the wood, extract cellulose and prepare cellulose paper. Immerse the cellulose paper in N,N-dimethylacetamide solution and react it fully at 160°C for 20 min. Then cool it down to 105°C, add lithium chloride and keep it warm for 30 min. The mass ratio of lithium chloride to N,N-dimethylacetamide solution is 1:10. Let it stand for 10 min, wash it with water to obtain Comparative Example 2 paper, wash it with anhydrous ethanol, and place it in a hot press at 60°C and 20MPa until it is completely dry.

[0070] The SEM images of the water-resistant paper obtained in Comparative Example 2 are shown below. Figure 4 Its thickness is 40μm, its dry tensile strength can reach 3.95KN / m, its wet tensile strength can reach 0.54KN / m, and its wet strength retention rate is 13.67%.

[0071] like Figure 5 The image shown is of the raw paper (see SEM image of the raw paper). Figure 2 The wet tensile strength graphs of the water-resistant paper prepared in Examples 1, 1 Comparative Example, and 2 are shown in the figures. It is clear from the figures that the wet tensile strength of the water-resistant paper prepared in Example 1 is significantly better than that of the original paper and the water-resistant papers in Comparative Examples 1 and 2, indicating that the water resistance of the water-resistant paper of the present invention has been significantly improved.

Claims

1. A super water-resistant paper, characterized in that, This super water-resistant paper is a dense structure composed of twisted and entangled microfibers and in-situ regenerated fibers. The in-situ regenerated nanofibers form a dense membrane structure that tightly wraps the connection points of the microfibers. The preparation method of the super-strong water-resistant paper includes the following steps: Cellulose paper is immersed in treatment solution A to obtain a first intermediate; the treatment solution A is one or more of sodium hydroxide solution, calcium hydroxide solution, and potassium hydroxide solution; The first intermediate is immersed in treatment solution B to dissolve part of the fiber, thereby obtaining the second intermediate; the treatment solution B is one or more of the following: alkali / urea mixed solution, lithium chloride / NN dimethylacetamide solution, N-methylmorpholine-N-oxide solution, ionic solution, and copper ammonia solution; The second intermediate is washed and dried to obtain super water-resistant paper.

2. The super water-resistant paper according to claim 1, characterized in that, The ultra-strong water-resistant paper has a wet tensile strength of 2.85–9.5 kN / m, a dry tensile strength of 7.6–11.4 kN / m, and a wet strength retention rate of 25%–83%.

3. The ultra-strong water-resistant paper according to claim 1, characterized in that, The ultra-strong water-resistant paper has a thickness of 50–200 μm and a density of 1.0–1.4 g·cm³. -3 .

4. A method for preparing the ultra-strong water-resistant paper according to any one of claims 1-3, characterized in that, Includes the following steps: Cellulose paper is immersed in treatment solution A to obtain a first intermediate; the treatment solution A is one or more of sodium hydroxide solution, calcium hydroxide solution, and potassium hydroxide solution; The first intermediate is immersed in treatment solution B to dissolve part of the fiber, thereby obtaining the second intermediate; the treatment solution B is one or more of the following: alkali / urea mixed solution, lithium chloride / NN dimethylacetamide solution, N-methylmorpholine-N-oxide solution, ionic solution, and copper ammonia solution; The second intermediate is washed and dried to obtain super water-resistant paper.

5. The method for preparing the ultra-strong water-resistant paper according to claim 4, characterized in that, The cellulose in the cellulose paper is derived from woody plants, vines, or herbaceous plants.

6. The method for preparing the ultra-strong water-resistant paper according to claim 4, characterized in that, The concentration of the A treatment solution is 1% to 20%, and the treatment temperature is 0 to 60°C.

7. The method for preparing the ultra-strong water-resistant paper according to claim 4, characterized in that, The dry weight of the cellulose paper and the mass ratio of the A treatment solution are 1 to 5:

30. The A treatment solution is used to soak the paper in the A treatment solution at 0 to 60°C for 10 minutes to 5 hours, and then wash it with water after treatment.

8. The method for preparing the super-strong water-resistant paper according to claim 4, characterized in that, The treatment temperature of the B treatment solution is -20 to 170°C, and the treatment time is 5 min to 5 h.

9. The method for preparing the super-strong water-resistant paper according to claim 4, characterized in that, The second intermediate obtained after treatment with solution B needs to be allowed to stand for 1–30 minutes.

10. The method for preparing the super-strong water-resistant paper according to claim 4, characterized in that, The drying methods include air drying at room temperature, oven drying, or hot pressing drying, with a drying temperature of 20–120°C.

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