Printing paper and its preparation and deinking method

Abstract

The present invention discloses a printing paper and a preparation and deinking method thereof. The preparation method of the printing paper comprises soaking cellulose paper in a strong alkaline solution of appropriate concentration, rinsing to neutrality after soaking for an appropriate time, drying and flattening to obtain water-washable printing paper. The surface fibers of the printing paper change from flat to steep after contacting water. Based on the characteristics of the printing paper, the present invention provides a water-washing and deinking method. The water-washable printing paper prepared in the present invention can be deinked and recycled without destroying the paper structure by artificially controlling the change in fiber morphology, and the carbon powder removal rate can reach 99.9%. The preparation and deinking method of the water-washable printing paper is simple in process, simple in instruments and equipment, and low in production cost, and can be applied to large-scale industrial production. The water-washable printing paper is composed of conventional micron plant fibers, does not contain other additives, is completely biodegradable, and can be used to partially replace existing office printing paper, etc.

Description

Technical Field

[0001] The present invention relates to paper and a preparation method thereof, in particular to washable printing paper and a preparation and deinking method thereof. Background Art

[0002] Paper, made from plant fibers, offers advantages such as low cost, ease of use, and biodegradability. However, its single-use nature leads to resource waste and recycling challenges. Therefore, promoting paper recycling is crucial, especially in office printing environments. Recycling printing paper not only extends its lifespan but also reduces dependence on forest resources, thereby achieving more sustainable resource management.

[0003] Currently, the industrial-grade waste paper recycling process mainly includes steps such as deinking, pulping, and recycled paper. This process not only has many steps and high costs, but also causes significant environmental pollution. Existing technological advances in paper recycling also have some limitations: for example, the technology of removing carbon powder from the surface of paper through mechanical abrasion may often cause structural damage to the paper; or the use of chemical solvents to dissolve carbon powder on the surface of paper. This method may require a large amount of chemical agents and bring potential environmental impacts; there is also a method that uses special specialty inks, but the cost of this ink is relatively high. These technical solutions all have bottlenecks that are difficult to meet large-scale application. Therefore, from a broader perspective, current technical means have not yet effectively addressed the practical challenges of paper recycling while ensuring a balance between economic benefits, operational convenience and sustainable development. Summary of the Invention

[0004] Objectives of the Invention: The present invention provides a method for preparing printing paper that addresses the problem of modifying paper fibers. Another objective is to provide printing paper that addresses the problem of existing printing paper being unable to be de-inked by water washing. A third objective is to provide a method for de-inking the aforementioned printing paper that addresses the problem of removing toner from the surface of printing paper.

[0005] Technical solution: The method for preparing printing paper of the present invention comprises soaking cellulose paper in a strong alkaline solution with a mass percentage concentration of 10%-20%, soaking for 10 minutes to 48 hours, then rinsing to neutrality, drying and flattening to obtain printing paper.

[0006] Soaking in lye causes paper fibers to shrink and entangle, improving the paper's mechanical stability in water. Furthermore, soaking in an appropriately concentrated lye solution can cause the paper's surface fibers to warp when exposed to water, reducing the contact area between the fibers and the toner, making it easier for the toner to fall off the fibers.

[0007] Preferably, the fiber source of the cellulose paper includes at least one of natural wood, cotton, linen and bamboo.

[0008] Preferably, the strong alkaline solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution.

[0009] Preferably, the flattening method is: maintaining the pressure on the paper at a pressure of 0.1 MPa-10 MPa for at least 10 minutes.

[0010] The present invention adopts the above-mentioned preparation method to prepare a kind of washable printing paper.

[0011] The surface fibers of the printing paper swell when exposed to water, and the gaps between the fibers become larger, causing the surface fibers to become steeper instead of flat. The steep surface fibers are not conducive to the adhesion of toner, and the toner will fall off quickly during the washing process to achieve the purpose of de-inking.

[0012] The present invention further provides a paper deinking method based on the characteristics of the above-mentioned printing paper, which comprises soaking the printed printing paper in water, washing the paper with water to remove the carbon powder on the surface of the printing paper, taking out the printing paper, drying it, and then flattening it.

[0013] Preferably, the printing method is toner-based laser printing or inkjet printing.

[0014] Preferably, the water washing method includes at least one of ultrasonic cleaning, mechanical friction cleaning in water, hydraulic cleaning, and vibration cleaning. The water-based cleaning method causes less damage to the paper and is conducive to the reuse of the paper.

[0015] Preferably, the water washing time is 10s-30min.

[0016] Preferably, the flattening method is: maintaining the pressure on the paper at a pressure of 0.1 MPa to 10 MPa for at least 10 minutes. The flattening operation can restore the steep surface fibers after washing to a flat state for further printing.

[0017] The invention uses ordinary fiber paper without additives as raw material, controls the microstructure of the paper by artificially controlling the morphological changes of the fibers, and obtains washable printing paper with new macroscopic properties, as well as a preparation method and deinking method thereof.

[0018] Beneficial Effects: Compared with existing technologies, the present invention offers the following significant advantages: 1. The water-washable printing paper of the present invention can be de-inked and recycled without damaging the paper structure, achieving a toner removal rate of up to 99.9%. 2. The water-washable printing paper is composed of conventional micron plant fibers and contains no additives, making it completely biodegradable and environmentally friendly, and can be used to partially replace existing office printing paper. 3. The preparation and de-inking methods for the water-washable printing paper are simple, require simple equipment, and have low production costs, making them suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a scanning electron microscope image of the present invention;

[0020] Figure 2 It is a recycling flow chart of the present invention;

[0021] Figure 3 This is a scanning electron microscope cross-sectional morphology image of the present invention before soaking in water;

[0022] Figure 4 This is a scanning electron microscope cross-sectional morphology image of the present invention after being soaked in water;

[0023] Figure 5 This is a scanning electron microscope image showing that the carbon powder of the present invention has fallen off in blocks after being washed in water. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1: A method for preparing washable printing paper is as follows:

[0026] Ordinary cellulose paper with no additives and whose fibers are derived from wood is soaked in an 18% by mass sodium hydroxide solution for 1 hour. The resulting paper sample is then taken out and washed in water until the residual alkaline solution on the surface of the paper is removed. The paper sample is then dried and placed in a press and pressurized perpendicularly to the paper surface at 0.5 MPa for 1 hour to obtain washable printing paper.

[0027] like Figure 1 and Figure 3 As shown in the figure, the surface fibers of the washable printing paper are flat before printing, but become steep after contacting water, as shown in the figure. Figure 4 shown.

[0028] The deinking and recycling method of the above printing paper is as follows:

[0029] After laser printing on washable paper, the pattern was placed in water and ultrasonically cleaned for one minute. The toner was completely removed after one minute. The paper was then dried and pressurized at 0.5 MPa for one hour to produce reusable, washable paper. This paper can be washed and de-inked multiple times.

[0030] from Figure 3 and Figure 4 By comparison, it can be seen that the fibers swell when exposed to water, the gaps between the fibers become larger, and the surface fibers become steeper from flat. Figure 5 The laser-printed pattern on the washable printing paper prepared in Example 1 is shown in a scanning electron microscope image showing that the carbon powder falls off in blocks after being washed in water. As can be seen from the image, as the surface fibers become steeper from flat, the carbon powder is subjected to uneven force and falls off in blocks, thereby achieving the purpose of cleaning.

[0031] Example 2: The rest is the same as Example 1, except that:

[0032] Additive-free, cotton-derived cellulose paper was soaked in a 10% sodium hydroxide solution for one hour. The resulting paper sample was then washed in water until any residual alkaline solution on the surface was removed, dried, and then pressed perpendicularly to the paper surface at 0.1 MPa for one hour in a press to produce washable printing paper. After laser printing, the paper was ultrasonically cleaned in water for one minute, completely removing the toner. The paper was then dried and pressed at 1 MPa for another hour to produce the reusable, washable printing paper.

[0033] Example 3: The rest is the same as Example 1, except that:

[0034] Additive-free, cotton-derived cellulose paper was soaked in a 20% sodium hydroxide solution for 10 minutes. The resulting paper sample was then washed in water to remove any residual alkaline solution from the surface, dried, and then pressed perpendicularly to the paper surface at 10 MPa for 10 minutes in a press to produce washable printing paper. The paper was then inkjet-printed with carbon powder and mechanically cleaned by friction in water. After 10 seconds, the carbon powder was completely removed. The paper was then dried and pressed at 3 MPa for 1 hour to produce the recyclable washable printing paper.

[0035] Example 4: The rest is the same as Example 1, except that:

[0036] Additive-free, wood-derived cellulose paper was soaked in a 15% potassium hydroxide solution for 10 minutes. The resulting paper sample was then washed in water to remove any residual alkaline solution from the surface, dried, and then pressed perpendicularly to the paper surface at 5 MPa for 1 hour in a press to produce washable printing paper. After laser printing, the paper was then immersed in clean water and shaken for 30 minutes to remove the toner. The paper was then dried and pressed at 5 MPa for 0.5 hour to produce the reusable washable printing paper.

[0037] Example 5: The rest is the same as Example 1, except that:

[0038] Additive-free, standard cellulose paper derived from hemp was soaked in a 13% lithium hydroxide solution for 24 hours. The resulting paper sample was then removed and rinsed in water to remove any residual alkaline solution from the surface. The sample was then dried and then pressed perpendicularly to the paper surface at 3 MPa for 1 hour in a press to produce washable printing paper. The paper was then laser-printed with a pattern and then washed in a washing machine. After 2 minutes, the toner was completely removed. The paper was then dried and pressed at 10 MPa for 10 minutes to produce the recyclable washable printing paper.

[0039] Example 6: The rest is the same as Example 1, except that:

[0040] Additive-free, ordinary cellulose paper derived from bamboo fibers was soaked in an 11% sodium hydroxide solution for 48 hours. The resulting paper sample was then removed and rinsed in water to remove any residual alkaline solution from the surface. After drying, the paper sample was then placed in a press and pressurized perpendicularly to the paper surface at 1 MPa for 1 hour to produce washable printing paper. After laser printing a pattern, the paper was rinsed with water, and the toner was completely removed after 15 minutes. The paper was then dried and pressurized at 0.1 MPa for 2 hours to produce the recyclable washable printing paper.

[0041] Comparative Example 1: The rest is the same as Example 1, except that:

[0042] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers in a 5% by mass sodium hydroxide solution for 1 hour.

[0043] Comparative Example 2: All other aspects are the same as Example 1, except that:

[0044] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers in a 25% by mass sodium hydroxide solution for 1 hour.

[0045] Comparative Example 3: The rest is the same as Example 1, except that:

[0046] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers in a 30% by mass sodium hydroxide solution for 1 hour.

[0047] Comparative Example 4: The rest is the same as Example 1, except that:

[0048] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers and no additives in a sodium hydroxide solution with a mass fraction of 18% for 5 seconds.

[0049] Comparative Example 5: The rest is the same as Example 1, except that:

[0050] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers and no additives in a sodium hydroxide solution with a mass fraction of 18% for 5 minutes.

[0051] Comparative Example 6: The rest is the same as Example 1, except that:

[0052] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers in an 18% by mass sodium hydroxide solution for 72 hours.

[0053] Comparative Example 7: The rest is the same as Example 1, except that:

[0054] Printing paper was prepared by soaking ordinary cellulose paper with wood fibers and no additives in a sodium hydroxide solution with a mass fraction of 18% for 55 hours.

[0055] Comparative Example 8: The rest is the same as Example 1, except that:

[0056] Additive-free, wood-derived cellulose paper was soaked in a 15% potassium hydroxide solution for one hour. The resulting paper sample was then washed in water to remove any residual alkaline solution from the surface, dried, and then placed in a press at 0.5 MPa, perpendicular to the paper surface, for one hour to produce washable printing paper. After laser printing on the paper, mechanical rubbing for 30 minutes in the dry state revealed a toner removal rate of only 5.3%, indicating virtually no de-inking effect on the dry paper.

[0057] The dry tensile strength, wet tensile strength and toner removal rate of the printing papers prepared in the examples and comparative examples were measured, and the results were as follows:

[0058] Table 1 Effects of different preparation parameters on the strength of printing paper and toner removal rate

[0059]

[0060] As shown in Table 1, the toner removal rates of Comparative Examples 1-7 were all lower than those of Example 1. If the alkali solution concentration and treatment time are not within the appropriate range, while water-resistant paper with a certain tensile strength can be produced, the paper cannot exhibit the surface fiber warping property when exposed to water, resulting in a significant reduction in toner removal rate. The paper produced in Examples 1-6 not only exhibits good dry and wet strength but also exhibits the surface fiber warping property when exposed to water. Only by possessing these two advantages can water-washing and deinking be possible. This invention solves the problem of toner adhering to paper and making it difficult to remove without damaging the paper structure.

Claims

1. A method for deinking and recycling washable printing paper, characterized in that: The printed washable printing paper is soaked in water, washed to remove carbon powder on the surface of the printing paper, taken out, dried and flattened to obtain recyclable washable printing paper; the preparation method of the washable printing paper is as follows: cellulose paper is soaked in a strong alkaline solution with a mass percentage concentration of 18%, soaked for 1 hour, rinsed to neutrality, dried and flattened to obtain the washable printing paper; wherein, the printing method is carbon powder-based laser printing; the washing method includes ultrasonic cleaning or mechanical friction cleaning in water; the strong alkaline solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution.

2. The deinking recycling method according to claim 1, characterized in that: The fiber source of the cellulose paper includes at least one of natural wood, cotton, hemp and bamboo.

3. The deinking recycling method according to claim 1, characterized in that: The flattening method is: maintaining the pressure on the paper at a pressure of 0.1 MPa to 10 MPa for at least 10 minutes.

4. The deinking recycling method according to claim 1, characterized in that: The water washing time is 10s-30min.

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