Recycling process of banknotes or specialty papers, fiber suspensions, regenerated fibers and their uses, and paper obtained therefrom

Abstract

The present invention relates to the field of the recovery or reuse of waste materials. The present invention discloses a method for recycling banknotes. The banknote manufacturing process generates a significant amount of waste, such as solid waste like paper that is rejected due to quality issues or printing defects, and therefore must be properly managed. The present invention aims to overcome the aforementioned problems and proposes a method for recycling current banknotes based on their composition. In this way, the recycling of scrap from the banknote manufacturing process highlights the importance of the circular economy and the importance of responsible resource use in the printing industry.

Description

Technology Field

[0001] The present invention is applicable to the field of recovery or utilization of waste materials. The present invention discloses a recycling process for waste materials generated in the banknote manufacturing process. Background Technology

[0002] The recycling of scraps and / or banknote paper generated from the banknote manufacturing process represents a fundamental practice in the sustainable management of waste generated by banknote printing companies. The banknote manufacturing process typically generates solid waste from printed or unprinted paper rejected due to quality issues, paper rejected for printing adjustments, paper resulting from printing press jams, trimming waste from the cutting process used to achieve the final banknote format, and printed banknotes rejected due to printing defects or any other unacceptable defects. To handle these rejects, printing facilities use specialized machinery to properly shred (de-characterize) the material into scrap, thereby preventing any improper use of the material after disposal or recycling.

[0003] These paper scraps can play a significant role in reducing waste and promoting sustainability. For example, when subjected to a recycling process, they can be used as a fiber source in the production of high-quality paper. This practice not only helps minimize environmental impact by reducing the amount of waste sent to landfills but also contributes to the conservation of natural resources by eliminating the need to manufacture paper from virgin raw materials.

[0004] In this context, to address the aforementioned problems, the present invention provides a recycling process for banknote paper based on the current composition of banknote paper. Accordingly, the recycling of scrap from the banknote manufacturing process exemplifies the importance of a circular economy and the responsible use of resources in the printing industry.

[0005] Prior art

[0006] Patent document PI 9605508-1 describes the development of a technology that enables the recycling of paper containing a formaldehyde-melamine-based chemical additive, a product commonly known as a wet-strength principle. Such paper (in this case, banknotes) is currently incinerated or disposed of in dumps and landfills because there is no domestic technology allowing its reuse by the recycling industry. Since these materials do not decompose or dissolve in water, but instead remain intact in the soil and leach printing inks and contaminants, they cause environmental and ecological problems. This technology was developed to enable the recycling of these materials and allows for the reuse of formaldehyde-melamine-impregnated paper. For this purpose, an alkali is used in combination to act on the chemical bonds of the formaldehyde-melamine system.

[0007] Unlike that disclosed in the aforementioned literature, current banknote paper uses epichlorohydrin resin as a wet strength (WS) enhancer. The discontinuation of the use of urea resin for this purpose is associated with its high toxicity. Although this product has historically been used in the papermaking industry to impart wet strength, this material, belonging to the formaldehyde resin family, is known for its toxicity as well as its strong and unpleasant odor. Depending on the change of chemical agent, the pulp is treated under neutral conditions at a pH of about 7. In the present invention, there is no need to immerse the pulp, and the process of the present invention is carried out under controlled pressure for a period of up to 6 hours.

[0008] Document CN109294034 discloses a method for converting waste banknotes into recycled composite materials. The method comprises the following steps: (1) obtaining pre-modified fibers by pre-treating waste banknotes and waste confidential documents to optimize the structure and morphology of the fibers; (2) weighing 30 to 50 parts by weight of pre-modified fibers, 52 to 67 parts by weight of recycled polyethylene particles, 1 to 3 parts by weight of maleic anhydride-grafted polyethylene, 0.5 to 1 part by weight of polyethylene wax, 0.1 to 0.2 parts by weight of a light stabilizer, and 0.1 to 0.2 parts by weight of an antioxidant 168; (3) The pre-modified fiber and recycled polyethylene pellets weighed in step (2) are placed in a high-speed mixer and thoroughly mixed, then maleic anhydride-grafted polyethylene, polyethylene wax, a light stabilizer, and an antioxidant are added sequentially, and the mixture is further blended with antioxidant 168 to obtain mixture I, and the mixture I is fed into a twin-screw flat extruder through a main feed port in a uniform feeding manner, and the material is extruded into pellets and sealed; (4) The extruded pellets obtained in step (3) are injection molded using an injection molding machine, then demolded and cooled to obtain a composite material.

[0009] Unlike the present invention, the above literature discloses that paper scraps containing a wet paper strength (WS) agent are modified as part of a polymer material and used as a raw material for an extruder.

[0010] Reference BR 10 2019 003165 4 describes the manufacture of polymer composites based on polypropylene and banknotes (banknotes of any denomination) for the production of polypropylene-based products. The polypropylene used can be raw and / or recycled. Blends of polypropylene and other polyolefins are also being considered to provide a viable alternative for significantly reducing the accumulation of such waste. This technology has enabled an efficient method for recovering banknote rejects unsuitable for circulation by manufacturing composites containing polypropylene without the need for pretreatment or resin impregnation of the banknotes. The choice of polypropylene is related to its extensive industrial use due to the variety of products manufactured from this polymer. In this technology, using existing production capacity, items typically manufactured from polypropylene were produced using composites made from raw and / or recycled polypropylene and banknotes. From composite materials produced in this way, it is possible to mold items used in the automotive and packaging industries, as well as manufacture toys, furniture, and other products.

[0011] Unlike the present invention, the above document discloses the reuse of banknotes as a constituent material of a polymer composite intended for the manufacture of a new product. The problem to be solved

[0012] The banknote manufacturing process generates solid waste, such as paper that is rejected due to quality issues and printing defects; since this produces a significant amount of waste, it must be properly managed. means of solving the problem

[0013] In this context, to address the aforementioned problem, the present invention provides a process for recycling existing banknotes based on the composition of the existing banknotes. In this way, the recycling of scrap generated from the banknote manufacturing process highlights the importance of the circular economy, the responsible use of resources in the printing industry, the reduction of raw fiber consumption during paper manufacturing, and the reduction of the volume of waste sent to landfills. Brief explanation of the drawing

[0014] FIG. 1 illustrates a simplified process flow diagram including step (c); FIG. 2 illustrates a material to be recycled; Figures 3 and 4 illustrate the final product obtained in step (c). Specific details for implementing the invention

[0015] The present invention can be better understood from the following detailed description together with the accompanying drawings.

[0016] As illustrated in part of FIG. 1, the present invention discloses a process for recycling special paper or security paper, said process being:

[0017] (a) A step of performing thermal and chemical treatment of the material to be recycled by pressure cooking; and

[0018] (b) It includes the step of washing the above material.

[0019] Special paper or security paper is defined as paper currency, wine labels, sandpaper, passports, decorative paper, stamps, official documents, etc., containing moisture-resistant resin (MR).

[0020] The material to be recycled is specialty paper or security paper, preferably composed of 100 wt% cotton and a wet strength resin content (RU) exceeding 0.25 wt% of the final paper (1,000 kg cotton paper / 2.50 kg resin), and said material to be recycled is waste from banknote manufacturing or any other source, such as banknotes recovered from circulation, which does not require, for example, pre-washing. Additionally, while the size of the material used in the process may vary; however, since a larger contact area enhances the associated chemical reactions, it is recommended to use shredded material, as shown in FIG. 2. Nevertheless, size is not a limiting factor.

[0021] The above process is performed in batches, and thus, in step (a), the material is weighed according to the equipment used in the process, for example, 1,000 kg or 2,000 kg. The material undergoes heat and chemical treatment to break down into reusable fibers, reduce the original wet strength of specialty paper or security paper, dissolve polyester-based security threads, and disperse various inks, metallic pigments, resins, and varnishes used in the banknote printing process.

[0022] Thermal and chemical treatments are performed in equipment that agitates the contents during the digestion process, such as rotary autoclaves or digesters of spherical or cylindrical shape. Ideally, this equipment is manufactured of carbon steel and coated externally with insulating material to improve heat transfer and minimize heat loss.

[0023] For example, 10.8 m 3 The capacity of the spherical digester with a volume of 1,000 kg of material per batch is 23 m 3 The capacity of the cylindrical digester with the volume is 2,000 kg of material per batch.

[0024] 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 wt% to 50.5 wt%, preferably 50 wt%. The ratio used in the process consists of a mixture of 2 parts water and 0.1 parts alkaline agent per 1 part (by volume or weight) of the material to be recycled; for example, 1,000 kg of the material to be recycled and 100 L of the alkaline agent are used per 2,000 liters of water. The water quality of the water to be used is constant; for example, industrial water having a color standard > 30 uc and turbidity > 2.0 NTU may be used. After loading the material to be recycled, water, and alkaline solution into the equipment, it is hermetically sealed to start the pressurized digestion process.

[0025] The internal pressure of the equipment is increased from 4.3 bar to 4.7 bar and is controlled, for example, by introducing saturated steam from a boiler within the company's facility area.

[0026] During the above process, motion, preferably rotational motion, is applied to homogenize the material to ensure that the chemical interacts uniformly with the chips being processed.

[0027] When the digestion process, which can take up to 7 hours for the material, is completed, the pressure inside the equipment is gradually released through relief valves over a period of up to 3 hours, for example, to atmospheric pressure (1 atm = 101325 Pa). Once the digestion equipment is depressurized, the airtight lid is opened, and the processed material is transferred to a tank, from where it will be supplied to the subsequent step of the material washing process.

[0028] In step (b), the material is washed, preferably under moderate stirring, to lower the pH of the medium. The washing process includes the step of adding water having a pH close to 7 to the tank, and the step of immersing the material just digested in the equipment as described in step (a) for an average of 3 hours. Optionally, the washing process can be accelerated by lowering the pH by adding 11 to 12% w / w aluminum sulfate having a pH of 3.0 to the 1% solution at a ratio of 0.02 parts aluminum sulfate to 1 part recycled material (volume / mass). Subsequently, the water is drained, and fresh water is added to the washing tank. Throughout the washing process, the pH of the suspension is monitored; When a value of 7.0 to 8.0 is reached, the process is completed, and a fibrous suspension having a neutral pH is produced, which can be used to manufacture any product using this raw material, including any other product of paper and fiber origin.

[0029] The fiber suspension obtained from the above process has a neutral pH of 7.0 to 8.0 and a moisture content of 50%.

[0030] To manufacture specialty paper, an additional step of moisture removal (step (c)) may be added to the above process. This extraction process facilitates the use of the fiber suspension in the papermaking process.

[0031] In step (c), water is removed from the material after washing by draining water from the fiber suspension through gravity dewatering on a forming screen, such as one made of polyester; then, the material is pressed using a wet press, preferably with a pneumatic pressure of, for example, 3 to 4 bar, until the moisture content in the recycled material reaches up to 50%.

[0032] Optionally, the wet press can be lined with felt.

[0033] The above process cannot completely remove color from the base material, and the resulting fiber still contains a certain amount of particles from pigments, protective yarns, etc.

[0034] The total amount of material loss is estimated to be about 10% of the original amount of banknote scrap purchased.

[0035] At the end of step (c), as shown in FIGS. 3 and 4, regenerated fibers are obtained that can be used to manufacture paper and any other fiber-based products.

[0036] The fiber obtained from the process including step (c) has a pH of 7.0 to 8.0, an average moisture content of 10 to 50%, and a bright, opaque color.

[0037] Accordingly, the specialty paper produced by the process of the present invention can be obtained directly from step (b) using a fiber suspension or from fibers obtained after step (c).

[0038] The fiber suspension mentioned above, as well as the fibers obtained from the process, can be used to manufacture paper, or any other fiber-based products, particularly packaging, sanitary mats, and sound insulation.

[0039] In this way, any paper product, such as specialty paper, banknotes, passports, and revenue stamps, or any other product of fiber origin, can be manufactured if one of its components is a fiber suspension or fiber obtained by the process of the present invention.

[0040] As can be seen, the present invention promotes a circular economy for banknote waste, a product that has previously been impossible to recycle for the manufacture of the base product, paper. This reduces dependence on raw materials and provides cotton fiber, a valuable renewable feedstock option for the paper industry.

[0041] The present invention will be illustrated by the following examples, but is not limited to or in these examples.

[0042] Examples

[0043] Example 1: Preparation of special recycled paper using fibers obtained from additional step (c)

[0044] To manufacture a special type of recycled paper, the fibers obtained in step (c) undergo a process of decomposing the fiber raw material. That is, the material passes through a tank equipped with rotating blades, and the rotating blades decompose the material and supply it into the tank. The mixture is prepared with a consistency (mass concentration) of about 5%; that is, 5% consistency means a ratio of 5 g of fiber material (solid) to 100 g of water (liquid).

[0045] Subsequently, this disaggregated pulp passes through a rotating blade to modify the fibers into a form required for papermaking, wherein the following parameters may be optionally controlled: inlet and outlet pressures (2.5 to 4.0 Pa), the current of the equipment (which must be constant), and the Schopper degree (°SR - a unit of measurement referring to the degree of drainage of the fiber suspension) according to the desired specifications for the final paper.

[0046] This purified pulp is sent to a tank, where additives such as dyes and bleaching agents are added while continuously administering binders, starches, retention aids, coagulants, mineral fillers, and other components according to the desired characteristics of the final product. The purified pulp is purified in various centrifugal purifiers to remove some of the impurities, supplied through a distributor to the headbox of a paper machine, and then flows into a tank that supplies the paper machine.

[0047] The headbox distributes this fiber suspension through a metering lip onto a flat table (Fourdrinier), the function of which is to form paper by draining the suspension onto a perforated plastic screen. At the end of this step, the continuous sheet of paper has a dry content of about 20%.

[0048] Afterwards, the sheet is passed through a press equipped with felt to absorb water squeezed out by pressure until it reaches a dry content of about 40%.

[0049] Next, the sheet is passed through a steam-heated cylinder to dry it until the moisture content of the final product reaches about 5%.

[0050] During the drying process, the paper web can undergo a surface sizing treatment (typically using modified starch) in a dosing unit referred to as a size press to improve specific properties of the paper.

[0051] After this process, the paper is dried again using a steam-heated cylinder or an infrared dryer.

[0052] Some papers still undergo mechanical processing using heated steel or rubber-coated calenders to improve the uniformity of the paper surface (smoothness, roughness) and adjust the thickness of the product to some extent.

[0053] Next, the paper is wound onto reels and separated from the paper machine.

[0054] These rolls, known as jumbo rolls, are intended for use in a finishing machine referred to as a rewinder, in which these rolls are wound under tension and cut into reels of the required width.

[0055] Next, these rolls are packaged for shipment and sale, or fed into slitting machines, where they are cut into sheets and subsequently packaged for sale.

[0056] The present invention has been disclosed in the foregoing description in terms of preferred embodiments. However, other modifications and variations are possible based on this description and are still within the scope of the invention disclosed herein.

Claims

Claim 1 A process for recycling specialty paper or security paper, wherein the process comprises: (a) a step of performing thermal and chemical treatment of a material to be recycled by cooking under pressure, wherein the material to be recycled undergoes thermal and chemical treatment in equipment that provides stirring during the cooking step, and water and an alkaline agent are administered to the material to be recycled, wherein the concentration of the alkaline agent is 48.5 wt% to 50.5 wt%; wherein the ratio includes an input charge of 2 parts of water and 0.1 parts of alkaline agent per 1 part (volume / weight) of the material to be recycled; and after the material to be recycled, water, and the alkaline agent solution are loaded into the equipment, the equipment is hermetically sealed to start the cooking under pressure process, and the internal pressure is raised and controlled to 4.3 to 4.7 bar by introducing saturated steam; A process characterized by comprising: (a) a step of gradually releasing the equipment pressure to atmospheric pressure upon completion of the digestion step to allow the opening of a sealed cover and transferring the processed material to a tank; and (b) a step of washing the material, wherein the washing is performed under stirring; wherein the washing process comprises the steps of introducing water having a pH close to 7 into the tank and immersing the freshly digested material immediately after processing from step (a) for 3 hours; subsequently, removing the water and adding new water to the washing tank; and wherein, throughout the washing, the pH of the suspension is controlled and the process is terminated when it reaches a value of 7.0 to 8.0 to obtain a fibrous suspension. Claim 2 A process according to claim 1, wherein the material to be recycled is special paper or security paper, preferably having a composition of 100 weight% cotton and an amount of wet-strength resin (RU) exceeding 0.25% of the paper. Claim 3 A process according to claim 1 or 2, wherein the size of the material used in the process is variable, and preferably, the material is shredded. Claim 4 A process according to paragraph 3, characterized in that the equipment providing stirring during the digestion step comprises a spherical or cylindrical rotary autoclave or digester made of carbon steel and coated with an insulating material on the outside. Claim 5 A process according to claim 4, characterized in that aluminum sulfate is additionally added as a 1% solution of 11 to 12% w / w and pH 3.0 at a ratio of 0.02 parts of aluminum sulfate per 1 part (volume / mass) of recycled material. Claim 6 A process according to claim 5, wherein the process further comprises a step (c) for manufacturing special paper, namely a water extraction step, wherein the step (c) is performed by removing water from the fiber suspension through gravity drainage on a forming wire and subsequently pressurizing the material, preferably by a wet press, to a moisture content of up to 10%. Claim 7 A process according to claim 6, characterized in that the wet press is additionally coated with felt. Claim 8 A fiber suspension obtained by a process defined in claim 1, characterized by comprising a neutral pH of 7.0 to 8.0 and a moisture content of 50%. Claim 9 A recycled fiber obtained by removing water from a fiber suspension defined in claim 8, characterized by having a pH of 7.0 to 8.0, an average moisture content of 10% to 50%, and a bright, opaque color tone. Claim 10 A use of a fiber suspension as defined in paragraph 8, wherein the use is for the manufacture of paper or fiber products. Claim 11 A use of recycled fibers as defined in paragraph 9, wherein the use is for the manufacture of paper or fiber products. Claim 12 A paper or fiber product, wherein the paper or fiber product comprises a fiber suspension as defined in claim 8. Claim 13 A paper or textile product, wherein the paper or textile product comprises recycled fibers as defined in claim 9.

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