A method for preparing a high-toughness specialty paper

Abstract

The application discloses a kind of high tenacity special paper preparation methods.This method uses cellulose nanofiber as raw material, by introducing small molecule competitive hydrogen bond effect, destroy the original hydrogen bond network of cellulose and induce molecular chain rearrangement, realize the topological isomerization transformation of cellulose crystal form, so as to significantly improve the fiber surface activity and the adjustable combination between fibers.On this basis, by wet forming and post-processing, the interaction between fibers is regulated, and a paper structure with high strength and high toughness is constructed.The obtained paper significantly improves the breaking elongation and tear resistance while maintaining high tensile strength, overcoming the technical bottleneck that traditional cellulose paper strength and toughness are difficult to consider, suitable for high-performance packaging, functional substrate and flexible device field.

Description

Technical Field

[0001] This invention belongs to the field of cellulose material processing and functional paper preparation technology, specifically relating to a method for preparing high-strength and tough cellulose paper based on topological isomerization mechanism by regulating the structure of cellulose molecular chains and the interaction between fibers. Background Technology

[0002] Cellulose paper is widely used in packaging materials, information carriers, and functional substrates due to its wide availability, renewability, and biodegradability. However, traditional cellulose paper generally suffers from a trade-off between strength and toughness in terms of mechanical properties. Typically, enhancing the hydrogen bonding between fibers can improve paper strength, but this leads to increased brittleness and reduced elongation at break; while weakening the interactions between fibers to improve toughness often comes at the cost of strength.

[0003] In existing technologies, methods to improve the strength and toughness of paper mainly include chemical crosslinking, surface coating, composite reinforcement, or the introduction of polymeric additives. However, these methods generally suffer from problems such as complex processes, heavy environmental burden, damage to the intrinsic fiber structure, or unstable reinforcement effects, making it difficult to fundamentally resolve the inherent contradiction between the strength and toughness of cellulose paper. Therefore, there is an urgent need for a preparation method that can reconstruct the fiber bonding mode and simultaneously improve the strength and toughness of paper without significantly damaging the main structure of cellulose. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-strength and tough paper based on topological isomerization. By controlling the configuration of cellulose molecular chains and the interaction between fibers, the paper strength and toughness are synergistically improved, thereby overcoming the shortcomings of existing technologies that make it difficult to balance the mechanical properties of paper.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing high-strength and tough specialty paper, comprising the following steps:

[0007] S1. Using cellulose nanofibers as raw material, a small molecule agent is introduced into their suspension for topological isomerization treatment. The small molecule agent forms competitive hydrogen bonds with the cellulose hydroxyl groups, disrupting the original hydrogen bond network of cellulose and inducing rearrangement of cellulose molecular chains, thereby achieving a topological isomerization transformation of the cellulose crystal form from type I to type III or a mixture thereof, thus improving the accessibility of hydroxyl groups on the fiber surface; the small molecule amine agent is removed by centrifugation; the small molecule agent is an amine, an alcohol amine, or a combination thereof.

[0008] S2. The cellulose nanofibers that have undergone topological isomerization are dispersed to obtain a uniform and stable fiber suspension system; the fiber suspension system is formed into a paper structure using a wet forming process and then dried to regulate the bonding state between fibers, thereby obtaining cellulose paper with both high strength and high toughness, i.e., high-strength and high-toughness specialty paper.

[0009] Furthermore, in step S1, the mass-to-volume ratio of the suspension to the small molecule agent is 500g:200mL, and the mass fraction of the suspension is 2%.

[0010] Furthermore, the topological heterogeneity treatment in step S1 is carried out at a temperature of 60°C for 3 hours.

[0011] Further, the amine mentioned in step S1 is at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine; the alkanolamine is at least one of ethanolamine, diethanolamine, and triethanolamine.

[0012] Further, step S2 includes uniformly spraying the pulp onto a moving forming wire through a headbox, using gravity and vacuum filtration to achieve preliminary dewatering, forming a wet paper web; the wet paper web is further dewatered by mechanical extrusion in the press section, and then dried, calendered and slit to obtain high-strength and tough specialty paper.

[0013] Furthermore, the vacuum filtration pressure is -0.1 MPa, and the slurry loading speed is 0.1 m / min; the working linear pressure of the mechanical extrusion of the pressing section is 65 N / cm, and the dehydration is carried out to a dryness of 40%.

[0014] Furthermore, the drying temperature is 65°C, and the drying is carried out until the moisture content is 5%.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] (1) By regulating the molecular chain structure of cellulose through topological isomerization, the bonding mode between fibers can be improved without destroying the main strength of the fiber.

[0017] (2) Achieve synergistic improvement in paper strength and toughness, effectively improving elongation at break and tear resistance;

[0018] (3) The process is simple and highly adaptable, and it is compatible with existing papermaking processes, and has good prospects for industrial application. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the cellulose crystal transformation in this invention;

[0020] Figure 2 The cyclic tensile properties of the high-strength and tough paper prepared in Example 1 are demonstrated. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the invention. Simple modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance thereof are all within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0022] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0023] Example 1

[0024] (1) Take 500 g of cellulose nanofiber suspension with a mass fraction of 2% as raw material, add 200 mL of ethylenediamine, and allow it to fully penetrate into the fiber interior to form competitive hydrogen bonds with the cellulose hydroxyl groups, thereby destroying the original hydrogen bond network and inducing molecular chain rearrangement. Then, after centrifugation at 6000 rpm for 10 minutes, remove the ethylenediamine to complete the topoisomerization treatment of cellulose (to transform the cellulose crystal form from type I to type III or a mixture thereof, thereby improving the accessibility of hydroxyl groups on the fiber surface).

[0025] (2) The cellulose nanofibers treated with topological isomerization are redispersed in water, and the slurry is evenly sprayed onto a moving forming wire through a headbox. Initial dehydration is achieved by gravity and vacuum suction, with a filtration pressure of -0.1 MPa, so that the fibers interweave to form a wet paper web. At this time, the sizing speed needs to be controlled at 0.1 m / min to avoid crossflow or cross-flow. The wet paper web is further dehydrated to 40% dryness by mechanical extrusion in the press section (working line pressure 65 N / cm), and then dried at 65℃ to a moisture content of 5%. Finally, the finished product, namely high-strength and tough specialty paper, is obtained by calendering and slitting.

[0026] Performance test results show that, while maintaining high tensile strength, the obtained paper exhibits a maximum tensile stress exceeding 32 MPa, a Young's modulus exceeding 20 MPa, and an energy dissipation coefficient less than 0.4 during 500 cycles of 10% tensile strain. Figure 2 ).

Claims

1. A method for preparing high-strength and tough specialty paper, characterized in that, Includes the following steps: S1. Using cellulose nanofibers as raw material, a small molecule agent is introduced into their suspension for topological isomerization treatment. The small molecule agent forms competitive hydrogen bonds with the cellulose hydroxyl groups, disrupting the original hydrogen bond network of cellulose and inducing rearrangement of cellulose molecular chains, thereby achieving a topological isomerization transformation of the cellulose crystal form from type I to type III or a mixture thereof, thus improving the accessibility of hydroxyl groups on the fiber surface; the small molecule amine agent is removed by centrifugation; the small molecule agent is an amine, an alcohol amine, or a combination thereof. S2. The cellulose nanofibers that have undergone topological isomerization are dispersed to obtain a uniform and stable fiber suspension system; The fiber suspension system is formed into a paper structure using a wet forming process and then dried. The bonding state between fibers is controlled to obtain cellulose paper with both high strength and high toughness, i.e., high-strength and high-toughness specialty paper.

2. The method according to claim 1, characterized in that, The mass-to-volume ratio of the suspension to the small molecule agent in step S1 is 500g:200mL, and the mass fraction of the suspension is 2%.

3. The method according to claim 1, characterized in that, The topological heterogeneity treatment in step S1 is carried out at a temperature of 60°C for 3 hours.

4. The method according to claim 1, characterized in that, The amine mentioned in step S1 is at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine; the alkanolamine is at least one of ethanolamine, diethanolamine, and triethanolamine.

5. The method according to claim 1, characterized in that, Step S2 includes uniformly spraying the pulp onto a moving forming wire through a headbox, and using gravity and vacuum filtration to achieve preliminary dewatering and form a wet paper web; The wet paper web is further dehydrated by mechanical extrusion in the press section, and then dried, calendered and slit to obtain high-strength and tough specialty paper.

6. The method according to claim 5, characterized in that, The vacuum filtration pressure is -0.1 MPa, and the slurry loading speed is 0.1 m / min; the mechanical extrusion working line pressure of the pressing section is 65 N / cm, and the dehydration is carried out to a dryness of 40%.

7. The method according to claim 5, characterized in that, The drying temperature is 65°C, and the product is dried to a moisture content of 5%.

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