Recycling process of banknotes or special paper, fiber suspension, regenerated fibers and their use, and the resulting paper

Abstract

This invention applies to the field of waste recycling or utilization. This invention discloses a process for banknote recycling. The banknote production process generates solid waste, such as paper scraps due to quality issues and printing defects, resulting in a large amount of waste that must be properly managed. Against this backdrop, to address the aforementioned problems, this invention provides a recycling process based on existing banknote components. In this way, the recycling of debris generated during banknote manufacturing reflects the importance of a circular economy and the responsible use of resources in the printing industry.

Description

Technical Field

[0001] This invention is applicable to the field of waste recycling or utilization. This invention discloses a process for recycling waste generated during the production of banknotes. Background Technology

[0002] The recycling of scrap and / or banknote paper generated during banknote production is a fundamental practice in the sustainable management of waste generated by banknote printing companies. Banknote production processes typically generate solid waste from printed or unprinted paper scrapped due to quality issues, paper scrapped due to printing adjustments, paper possibly generated due to printing press jams, cutting waste from the cutting process to obtain the final banknote dimensions, and printed banknotes scrapped due to printing defects or other unacceptable defects. To handle such waste, the material is properly shredded (cut into scrap) using specialized machinery in the printing facility to remove its characteristics and prevent any improper use of the material after disposal or recycling.

[0003] These shredded papers play a crucial role in reducing waste and promoting sustainable development. For example, when they undergo the recycling process, they can serve as a fiber raw material in the production of high-quality paper. This practice not only reduces environmental impact by decreasing the amount of waste sent to landfills, but also contributes to the protection of natural resources by avoiding the need to use virgin raw materials to produce paper.

[0004] Against this backdrop, to address the aforementioned problems, this invention provides a conventional banknote paper recycling process based on its composition. Therefore, the recycling of fragments from the banknote production process demonstrates the importance of a circular economy and the responsible use of resources in the printing industry.

[0005] Patent document PI 9605508-1 describes the development of a technology that enables the recycling of paper containing formaldehyde-melamine chemical additives, commonly referred to as wet strength agents. This type of paper, referring in this context to banknotes, is currently typically incinerated or discarded in landfills and dumps because there is no domestic technology to support recycling processes for its reuse. This leads to environmental and ecological problems because the material does not decompose or dissolve in water; instead, it remains intact in the soil, leaching printing ink and pollutants. This technology was developed to enable the recycling of such materials, allowing the reuse of paper impregnated with formaldehyde-melamine. For this purpose, an alkaline substance is used, acting on the chemical bonds of the formaldehyde-melamine system.

[0006] Contrary to the information disclosed in the aforementioned literature, current banknote paper uses epichlorohydrin resin as the wet strength agent (WS). The reason for discontinuing the use of urea-formaldehyde resin for this purpose is its high toxicity. Although this product was historically used in papermaking to impart wet strength, this substance, belonging to the formaldehyde resin family, is notorious for its strong and unpleasant odor and toxicity. With the change in chemicals, the pulp is processed under neutral conditions with a pH of approximately 7. In this invention, pulp soaking is not required, and the process is carried out under controlled pressure for up to 6 hours.

[0007] Document CN109294034 discloses a method for converting banknote waste into recycled composite materials. The method includes the following steps: Step 1, pretreating banknote waste and confidential paper waste to optimize the structure and morphology of the fibers, thereby obtaining pre-modified fibers; Step 2, weighing by weight: 30–50 parts pre-modified fibers, 52–67 parts recycled polyethylene granules, 1–3 parts maleic anhydride-grafted polyethylene, 0.5–1 part polyethylene wax, 0.1–0.2 parts light stabilizer, and 0.1–0.2 parts antioxidant 168; Step 3, placing the pre-modified fibers and recycled polyethylene granules weighed in Step 2 into a high-speed mixer, mixing thoroughly, and then sequentially adding maleic anhydride-grafted polyethylene, polyethylene wax, light stabilizer, and antioxidant. The mixture is further mixed with antioxidant 168 to obtain mixture I. Then, mixture I is fed evenly into a twin-screw flat extruder through the main feed port to extrude the material into granules and seal them. In step 4, the extruded granules obtained in step 3 are injection molded by an injection molding machine, then demolded and cooled to obtain a composite material.

[0008] Unlike the present invention, the above-mentioned documents disclose the conversion of paper scraps containing wet strength agent (WS) into part of a polymer material and its use as a raw material for an extruder.

[0009] Reference BR 10 2019 003165 4 describes the preparation of a polymer composite material based on polypropylene and banknotes (banknotes of any denomination) for the manufacture of polypropylene-based products. The polypropylene used can be virgin and / or recycled. Furthermore, the use of mixtures of polypropylene with other polyolefins is considered, aiming to provide a viable alternative to significantly reduce the accumulation of such waste. This technology provides an efficient method for recycling banknote waste unsuitable for circulation, based on the preparation of a polypropylene-containing composite material without the need for pretreatment or resin impregnation of the banknotes. The choice of polypropylene is related to its wide range of industrial applications, as this polymer can be used to make a wide variety of products. For this technology, existing production capacity is utilized to produce the same products typically made of polypropylene, using a composite material made from virgin and / or recycled polypropylene and waste banknotes. The produced composite material can be used for injection molding of articles for the automotive and packaging industries, as well as for the manufacture of toys, furniture, and other products.

[0010] Unlike this invention, the aforementioned documents disclose the reuse of banknotes as a component material in polymer composites used to manufacture new products. Summary of the Invention

[0011] The production of banknotes generates solid waste, such as paper discarded due to quality issues and printing defects, resulting in a large amount of waste that must be properly managed.

[0012] Against this backdrop, to address the aforementioned problems, this invention provides a process for recycling banknotes based on existing banknote components. In this way, the recycling of debris generated during banknote manufacturing reflects the importance of a circular economy, the responsible use of resources in the printing industry, the reduction of virgin fiber consumption during paper production, and the reduction of waste sent to landfills. Attached Figure Description

[0013] Figure 1 A simplified flowchart is shown, including step (c).

[0014] Figure 2 The materials to be recycled were displayed.

[0015] Figure 3 and Figure 4 The final product obtained in step (c) is shown. Detailed Implementation

[0016] The invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings.

[0017] like Figure 1 As shown in the figure, this invention discloses a process for recycling specialty paper or security paper, comprising the following steps: (a) Thermal and chemical treatment of the material to be recycled by pressure cooking; and (b) Washing materials.

[0018] Specialty paper or security paper is defined as: banknotes, wine labels, sandpaper, passports, decorative paper, stamps, official documents and other papers containing moisture-resistant resin (MR).

[0019] The material to be recycled is specialty paper or security paper, preferably composed of 100% cotton by weight, and with a wet-strength resin (RU) content exceeding 0.25% of the final paper (i.e., 1,000 kg cotton paper / 2.50 kg resin). This includes waste materials from banknote production or other sources, such as withdrawn banknotes that do not require pre-washing. Furthermore, the size of the raw materials used in the process may vary; however, it is recommended to use materials such as… Figure 2 The shredded raw materials shown are used because a larger contact area can enhance the chemical reactions involved. However, size is not a limiting factor.

[0020] The process is carried out in batches; therefore, in step (a), the raw materials need to be weighed according to the equipment used in the process—for example, 1,000 kg or 2,000 kg. The raw materials are heat-treated and chemically treated to break them down into reusable fibers, reduce the original wet strength of specialty or security paper, dissolve the polyester-based security thread, and disperse the various inks, metallic pigments, resins, and varnishes used in banknote printing.

[0021] Heat treatment and chemical treatment are carried out in equipment that agitates the contents during cooking, such as spherical or cylindrical cookers or rotary autoclaves. Ideally, such equipment should be made of carbon steel and coated with insulating material to improve heat conduction and minimize heat loss.

[0022] For example, a spherical cooking pot with a volume of 10.8 cubic meters has a capacity of 1,000 kg per batch, while a cylindrical cooking pot with a volume of 23 cubic meters has a capacity of 2,000 kg per batch.

[0023] The material to be recycled is mixed with water and an alkaline agent (preferably caustic soda). The concentration of the alkaline agent used is 48.5% to 50.5% by weight, preferably 50%. The ratio used in this process is 2 parts water and 0.1 parts alkaline agent (by volume or weight) for every 1 part of the material to be recycled; for example, 1,000 kg of the material to be recycled and 100 liters of alkaline agent are used for every 2,000 liters of water. The water used should be of consistent quality; for example, industrial water can be used, with a color standard greater than 30 uc (color units) and a turbidity greater than 2.0 NTU (turbidity units). After the material to be recycled, water, and alkaline solution are loaded into the equipment, it is sealed, and the pressurized cooking process is then started.

[0024] The internal pressure of the equipment is raised to between 4.3 and 4.7 bar by introducing saturated steam, for example, which can come from a boiler in the company's utility area.

[0025] During processing, motion—preferably rotational motion—is applied to the material to homogenize it, thereby ensuring that the chemicals interact uniformly with the processed debris.

[0026] After the materials have been cooked—a process that can take up to 7 hours—the pressure inside the equipment will be gradually released over a period of up to 3 hours, for example, by releasing it to atmospheric pressure (1 atm = 101325 Pa) through a pressure relief valve. Once the cooking equipment has completed depressurization, the sealing cover is opened, the treated materials are transferred to a tank, and then sent to the next stage: washing the materials.

[0027] In step (b), the material is washed to lower the pH of the medium, preferably with moderate agitation. The washing process involves adding water with a pH close to 7 to the tank and immersing the material that has just been cooked in the equipment—as described in step (a)—in it for an average of 3 hours. Optionally, 11-12% by mass of aluminum sulfate, with a 1% solution pH of 3.0, can be added at a ratio of 0.02 parts by volume / mass per part of the material to be recycled, to accelerate the washing process by lowering the pH. The water is then drained and fresh water is added to the washing tank. Throughout the washing process, the pH of the suspension is monitored; the process is complete when the pH reaches between 7.0 and 8.0, yielding a neutral fiber suspension suitable for producing any product using this material, including paper and any other fiber-derived products.

[0028] The fiber suspension obtained by this process is neutral, with a pH value between 7.0 and 8.0 and a water content of 50%.

[0029] To produce specialty papers, an additional step can be added to the process: dewatering (step c). This dewatering process facilitates the use of fiber suspensions during papermaking.

[0030] In step (c), after washing, the water in the fiber suspension is removed by gravity dehydration on a forming web (e.g., a forming web made of polyester) to remove moisture from the material; the material is then pressed, for example by applying an air pressure of 3 to 4 bar, preferably using a wet press, until the moisture content in the recycled material is reduced to 50%.

[0031] Optionally, the wet press may be lined with felt.

[0032] This process cannot completely remove the color from the base material, and the resulting fibers still contain a certain amount of particles from pigments, safety threads, etc.

[0033] The total material loss is estimated to be approximately 10% of the original amount of banknote scrap purchased.

[0034] At the end of step (c), recycled fibers are obtained, which can be used to produce paper and any other fiber-based products, such as... Figure 3 and Figure 4 As shown.

[0035] The process, including step (c), yields fibers with a pH value between 7.0 and 8.0, an average moisture content of 10% to 50%, and a light and opaque color.

[0036] Therefore, the specialty paper produced by the process of the present invention can be obtained directly from the fiber suspension in step (b), or from the fibers obtained after step (c).

[0037] The fiber suspension and the fibers obtained through this process can be used to manufacture paper or any other fiber-based products, such as packaging materials, sanitary pads, and sound insulation materials.

[0038] In this way, any paper product or any other fiber-derived product, such as specialty paper, banknotes, passports and tax stamps, can be produced, as long as one of its components is a fiber suspension or fiber obtained by the process of this invention.

[0039] As can be seen, this invention promotes a circular economy for a product—paper waste—which until now could not be reused to manufacture the basic product: paper. This reduces dependence on virgin raw materials and provides the paper industry with a valuable renewable raw material option: cotton fiber.

[0040] The present invention will be illustrated by the following examples, but is not limited to these examples.

[0041] Example Example 1: Producing specialty recycled paper using fibers obtained from additional step (c) To produce a specific type of recycled paper, the fibers obtained in step (c) undergo a process to break down the fiber raw material. In other words, the raw material passes through a trough equipped with rotating blades that break it down. The mixture is prepared to a concentration of approximately 5% (mass concentration); that is, a 5% concentration means a ratio of 5 grams of fiber material (solid) to 100 grams of water (liquid).

[0042] The dissociated pulp then passes through a rotating blade that adjusts the fibers as needed and selectively controls the following parameters: inlet and outlet pressure (2.5 to 4.0 Pa), the current of the equipment (which must be kept constant), and the Schubert freeness (°SR—a unit of measurement indicating the degree of drainage of the fiber suspension), which is controlled according to the required specifications of the final paper.

[0043] This refined pulp is fed into a tank where additives such as dyes and bleaching agents are added, along with a continuous, metered addition of binders, starch, retention aids, coagulants, mineral fillers, and other components, depending on the desired characteristics of the final product. The refined pulp is then purified in various centrifugal purifiers to remove some impurities and conveyed via distributors to the headbox of the paper machine, from where it flows into the feed trough for the paper machine.

[0044] The headbox delivers this fiber suspension to the flat wire (long wire) via a metering lip, where it is dehydrated through a perforated plastic mesh to form paper. At the end of this stage, the dry content of the continuous paper web is approximately 20%.

[0045] The paper web then passes through a press section fitted with felt to absorb the moisture squeezed out by pressure until its dry content reaches about 40%.

[0046] The paper web is then dried in a steam-heated drying cylinder until the final product has a moisture content of approximately 5%.

[0047] In the middle stages of the drying process, the paper web may undergo surface sizing (usually using modified starch) in a basis weight unit called sizing press to improve certain properties of the paper.

[0048] After this treatment, the paper is dried again using a steam-heated drying cylinder or an infrared dryer.

[0049] Some papers are also mechanically treated using heated steel rollers or calenders to improve the uniformity (smoothness, roughness) of the paper surface and to some extent adjust the thickness of the product.

[0050] The paper is then wound onto a reel and removed from the paper machine.

[0051] These paper rolls, known as master rolls, are used in a post-processing device called a rewinder, where they are wound under tension and cut into rolls of the required width.

[0052] These rolls can then be packaged for transport and sale, or fed into a slitting machine where they are cut into sheets and then packaged for sale.

[0053] The present invention has been disclosed in this specification in conjunction with its preferred embodiments. However, other modifications and variations can be made based on this specification, and these still fall within the scope of the disclosed invention. Claims (as amended under Article 19 of the Treaty) 1. A process for recycling specialty paper or safety paper, characterized by comprising the following steps: (a) The material to be recycled is subjected to heat treatment and chemical treatment by pressure cooking; wherein, during the cooking stage, the material to be recycled is subjected to heat treatment and chemical treatment in a device with a stirring function, and water and an alkaline agent are added to the material to be recycled in a measured amount, the concentration of the alkaline agent being 48.5% to 50.5% by weight; this ratio includes: 2 parts water and 0.1 parts alkaline agent per part of recycled material (volume / weight); wherein, after the material to be recycled, water and alkaline agent solution are added to the device, the device is sealed to start the pressure cooking process, and the internal pressure is raised to between 4.3 and 4.7 bar by introducing saturated steam and controlled; once the cooking step is completed, the pressure of the device is gradually released to atmospheric pressure so that the sealing cover can be opened and the treated material is transferred to a tank. as well as (b) Washing the material, wherein the washing is carried out under agitation conditions; the washing process includes adding water with a pH value close to 7 to a tank and soaking the material that was just boiled in step (a) for 3 hours; then draining the water and adding fresh water to the washing tank; throughout the washing process, the pH value of the suspension is controlled and the process is terminated when the pH value reaches between 7.0 and 8.0, thereby obtaining a fiber suspension. 2. The process according to claim 1, characterized in that the material to be recycled is special paper or safety paper, preferably composed of 100% cotton by weight, and containing more than 0.25% wet strength resin (RU) by weight of the paper. 3. The process according to claim 1 or 2, characterized in that the material size used in the process is variable, preferably the material being pulverized. 4. The process according to claim 3, characterized in that the equipment for providing stirring during the cooking stage includes a spherical or cylindrical cooking pot or a rotary autoclave, which is made of carbon steel and coated with heat-insulating material on the outside. 5. The process according to claim 4, characterized in that aluminum sulfate is further added at a mass percentage of 11-12% and the pH value of its 1% solution is 3.0, with a ratio of 0.02 parts aluminum sulfate to 1 part recycled material (volume / mass). 6. The process according to claim 5, characterized in that the process further includes a step (c) for producing specialty paper, namely dewatering, which removes water from the fiber suspension by gravity drainage on a forming wire, followed by pressing the material, preferably in a wet press, until its moisture content does not exceed 10%. 7. The process according to claim 6, characterized in that the wet press is further lined with felt. 8. A fiber suspension, characterized in that it is prepared by the process described in claim 1, and has a neutral pH value between 7.0 and 8.0 and a water content of 50%. 9. Regenerated fiber, characterized in that it is obtained by dehydration from the fiber suspension of claim 8, having a pH value between 7.0 and 8.0, an average water content of 10% to 50%, and a light and opaque color tone. 10. The use of the fiber suspension as defined in claim 8, characterized in that it is used in the production of paper or fiber products. 11. The use of the recycled fiber as defined in claim 9, characterized in that it is used in the production of paper or fiber products. 12. A paper or fiber article, characterized in that it comprises a fiber suspension as defined in claim 8. 13. A paper or fiber article, characterized in that it comprises recycled fibers as defined in claim 9.

Claims

1. A process for recycling specialty paper or safety paper, characterized in that, Includes the following steps: (a) The material to be recycled is subjected to heat treatment and chemical treatment by pressure cooking; as well as (b) Washing materials.

2. The process according to claim 1, characterized in that, The material to be recycled is specialty paper or safety paper, preferably composed of 100% cotton by weight and containing more than 0.25% wet strength resin (RU) by weight of the paper.

3. The process according to claim 1 or 2, characterized in that, The size of the material used in this process is variable, and it is preferably a pulverized material.

4. The process according to any one of claims 1 to 3, characterized in that, The process employs batch processing. In step (a), the material to be recycled undergoes heat and chemical treatment in a stirred apparatus during the cooking process. The material to be recycled is mixed with water and an alkaline agent, wherein the concentration of the alkaline agent used is 48.5% to 50.5% by weight. Each part of the material to be recycled (volume / weight) corresponds to 2 parts of water and 0.1 parts of alkaline agent. After the material to be recycled, water, and alkaline agent solution are added to the apparatus, the apparatus is sealed to begin the pressurized cooking process. During this process, the internal pressure is raised to between 4.3 and 4.7 bar by introducing saturated steam and is controlled. Once the material has been cooked, the pressure inside the apparatus is gradually released to atmospheric pressure so that the sealed cover can be opened and the treated material is transferred to a tank.

5. The process according to claim 4, characterized in that, The equipment used for stirring during the cooking stage includes spherical or cylindrical cooking pots or rotary autoclaves made of carbon steel and coated with heat-insulating material.

6. The process according to any one of claims 1 to 5, characterized in that, In step (b), the washing of the material is carried out under stirring conditions; wherein the washing includes adding water with a pH value close to 7 to the washing tank and soaking the material that was just boiled in step (a) for 3 hours; then draining the water and adding fresh water to the washing tank; throughout the washing process, the pH value of the suspension is controlled, and the process is terminated when the pH value reaches between 7.0 and 8.0, thereby obtaining a fiber suspension.

7. The process according to claim 6, characterized in that, Further add aluminum sulfate at a mass percentage of 11-12%, with a pH of 3.0 for a 1% solution, at a ratio of 0.02 parts aluminum sulfate to 1 part recycled material (volume / mass).

8. The process according to claim 6, characterized in that, The process also includes a step (c) for producing specialty paper, namely dewatering, which removes water from the fiber suspension by gravity drainage on a forming wire, followed by pressing of the material, preferably in a wet press, until its moisture content does not exceed 10%.

9. The process according to claim 8, characterized in that, The wet press is also lined with felt.

10. A fiber suspension, characterized in that, It is prepared by the process described in claim 1 and has a neutral pH value between 7.0 and 8.0 and a water content of 50%.

11. Regenerated fiber, characterized in that, It is obtained by dehydration from the fiber suspension of claim 10, having a pH value between 7.0 and 8.0, an average water content of 10% to 50%, and a light and opaque color tone.

12. The use of the fiber suspension as defined in claim 10, characterized in that, It is used to produce paper or fiber products.

13. The use of regenerated fibers as defined in claim 11, characterized in that, It is used to produce paper or fiber products.

14. A paper or fiber product, characterized in that, It includes the fiber suspension as defined in claim 10, or the regenerated fiber as defined in claim 11.

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