RU2850056C1 - Method for producing paper bases for sanitary and hygienic products from waste paper - Google Patents

Abstract

FIELD: recycling of secondary raw materials.

SUBSTANCE: present invention relates to the field of recycling secondary raw materials in the form of layered aluminised materials, namely to a method for producing base paper for sanitary and hygienic products from waste paper. The method involves breaking down waste paper, whereby before breaking down, the waste paper is freed from binding materials and liners and loosened, then mixed with water and broken down into secondary cellulose fibre, aluminium foil and polyethylene, the loosened cellulose mass is separated into a liquid mass with cellulose fibres, fine and coarse polymer-aluminium mixtures, the liquid mass with cellulose fibres and the fine polymer-aluminium mixture are fed to a separator for grinding to a uniform density, the coarse polymer-aluminium mixture is additionally cleaned of cellulose fibre residues, pressed, dry and form bales of polymer-aluminium mixture, clean the liquid mass with cellulose fibres from the fine fraction of the polymer-aluminium mixture in a conical mill and two pressure sorters, grind the cellulose fibres, dissolve the pure cellulose mass into fibres, split and comb the keratinised fibres of waste paper in a disc mill, after which the paper mass is sent to the pressure box of the paper-making machine and fed onto the screen of a rotating wire drum, the cellulose mass is dewatered and the base paper for sanitary and hygienic products is formed.

EFFECT: improved purification of cellulose fibres and strength characteristics of the base paper.

1 cl, 1 dwg

Description

The present invention relates to the processing of secondary raw materials in the form of laminated aluminized materials, namely MS-11V waste paper (Tetra Pak food packaging). The invention can also be used in the pulp and paper industry for the production of base paper for sanitary and hygienic products from recycled raw materials. Preferably, the present invention can be used to produce base paper and recycled raw materials in the form of a separate polymer-aluminum fraction from packaging waste, including a paper layer with a combined coating of polyethylene film and aluminum foil.

Methods for recycling multilayer aluminized packaging materials are known, characterized by the use of various chemicals. For example, a method (patent RU 2526067 C1, published August 20, 2014) involves shredding waste multilayer aluminized materials and chemically separating them into aluminum and paper-polymer pulp. Layer separation is performed in two stages: the first is mixing the waste multilayer aluminized materials in an acetic acid solution, and the second is frictional-pulsation separation in the same solution. After layer separation, aluminum particles and paper-polymer pulp are separately fed to the outlet. After feeding the aluminum particles to the outlet, they are sequentially washed with water, filtered, hydrocycloned, dried, and compacted. After feeding the paper-polymer mass mixed with dust and sludge to the outlet, they are sequentially washed with water, filtered, dried, crushed, mixed until a homogeneous state is achieved, and then secondary composite material is obtained by hot pressing and products are manufactured from the obtained secondary raw materials.

The main disadvantage of the known method of waste recycling is the use of acetic acid in the technological process, which has a hazard class of 3 and is considered a harmful chemical substance.

Patent document RU 2668873 C2, published October 4, 2018, describes a method for processing Tetra Pak packaging and separating it into three components: cellulose fibers, aluminum, and a polymer film. It is proposed to use hydrochloric acid for this process. Hydrochloric acid is a caustic substance classified as hazard class 3.

A known method for recycling packaging material (patent RU 2759556 C2, published November 15, 2021) involves separating multilayer material using methanoic acid (formic acid) and ethanol. Another disadvantage of this method is the use of harmful chemicals.

International application WO2023170496A2 (published 14.09.2023) discloses a method for processing waste, including waste paper, in a high-pressure vessel at elevated temperature and elevated processing pressure to form processed waste, which includes largely re-shredded waste paper; unloading the processed waste from the vessel under pressure; and subsequent separation of the processed waste using a screening device into re-shredded waste paper and large debris.

A disadvantage of the known method is the inclusion of pressure vessels (autoclaves) in the process flow, as vessels operating under excess pressure are highly hazardous. If depressurized, workers are at risk of thermal and chemical burns, as well as mechanical injuries.

There are also known methods for processing aluminized packaging materials by shredding and stratifying waste using various non-chemical methods, for example, the invention according to patent RU 2496639 C2, published on 27.10.2013, according to which shredding, stratification and defibering of waste into paper and aluminopolymer fractions are carried out; patent RU 2158182 C1, published on 27.10.2000, where stratification of layers, cutting and washing with water take place; the invention according to international application WO1997049494A1, published on 31.12.1997, according to which the waste processing technology takes place in a screw feeder and a refiner; US application for invention US5277758A, published on 11.01.1994, where waste processing is carried out by shredding and flotation with mixing; Chinese patent application CN102091714A, published June 15, 2011, describes a recycling method characterized by the following: after crushing with a crusher, paper-plastic composites are transferred to a wash tank for wet decomposition, and then the paper is removed using a paper remover to separate the paper and plastic. The separated paper is mixed with water to form a pulp, which is filtered and dehydrated to form the finished pulp. The separated plastic is then converted into plastic products using an extruder.

A common drawback of known waste recycling methods based on mechanical processing is the insufficient degree of purification of cellulose fibers from the polymer-aluminum component. This is due to the crushing and subsequent pressing of used raw materials. This results in a "mushy" composition of polyaluminum mixture and crushed cellulose, the layers of which are tightly bonded together, and the purification (separation) of these layers will be poor. The purification quality of the fine fraction using a simple wet process without the use of chemicals will be 70-80%, which is low for using this mixture as a separate raw material component in subsequent stages and will require additional resources for further purification of the polyaluminum mixture and separation of the cellulose fibers.

Furthermore, existing recycling methods involve shredding the waste before separating it into its components, such as by crushing. However, crushing can reduce the strength of the base paper obtained from the cellulose component, since the finer the crushed fraction, the lower the strength of the base paper.

Another significant drawback is that existing recycling methods focus on recycling and utilizing waste and producing secondary raw materials in the form of cellulose fiber and a polymer-aluminum mixture, or a separate aluminum fraction and a cellulose-polymer mixture, and do not allow for paper production in a single cycle with waste recycling. However, the resulting fibrous, cellulose pulp has a short shelf life in its wet state and therefore requires rapid subsequent processing to produce finished paper products; otherwise, it becomes unsuitable for further use.

The present invention relates to waste paper recycling, which involves the separation of cellulose fiber, which is the primary component in the production of base paper in the same process. The recycling of this type of waste paper, according to the present invention, does not involve the use of aggressive chemical components hazardous to human health. Furthermore, the base paper manufacturing process eliminates the use of pressure vessels (autoclaves). Furthermore, the present invention enables the purification of the resulting polyaluminum mixture, which is the primary component for aluminum and plastic manufacturers.

The closest approach to the proposed method for recycling laminated film is to cut the laminated film into multiple fragments to be processed. These fragments are then delaminated or separated by layer type by applying frictional impact forces to each fragment. The delaminated layers are then sorted using an air jet. The layers, collected in a mixed state, are sorted and stored separately. The fragment to be processed is washed with water before and after the stage of cutting the laminated film into multiple fragments to be processed, or during the stage of applying frictional impact forces to each of the processed fragments [patent RU 2158182 C1, published 27.10.2000].

The disadvantages of the closest analogue, as well as known mechanical methods of processing waste paper, are the unsatisfactory degree of purification of cellulose fibers due to the preliminary crushing of the material, as well as the low strength characteristics of the base paper, caused by mechanical damage to the cellulose fiber by shortening it, and, consequently, the formation of a non-plastic mass due to insufficient bonds between the fibers and, as a result, a fragile paper web at the output with increased dustiness, porosity and delamination during use.

The objective of the present invention is to improve the method for producing sanitary and hygienic base paper from waste paper made from various materials. The developed technology is based on separating waste paper into its constituent components: cellulose fiber and a polymer-aluminum mixture. Furthermore, a distinctive feature of the claimed method is the reduction of man-made impact on the natural environment, as well as the consumption of natural resources, energy costs, and toxic emissions by processing MS-11V waste paper through recycling processes.

The technical result that the present invention is aimed at achieving is to increase the degree of purification of cellulose fibers and the strength characteristics of the base paper.

The technical result is achieved in that the method for producing base paper for sanitary and hygienic products from waste paper made from various materials, including its splitting, according to the invention, before splitting, the waste paper is first freed from dressings and pads and loosened, then it is mixed with water and split into secondary cellulose fiber, aluminum foil and polyethylene, the dissolved cellulose mass is separated into a liquid mass with cellulose fibers, small and large polymer-aluminum mixtures, the liquid mass with cellulose fibers and the small polymer-aluminum mixture are fed to a separator for grinding to a uniform density, the large polymer-aluminum mixture is additionally purified from the remains of cellulose fibers, pressed, dried and bales of the polymer-aluminum mixture are formed, the liquid mass with cellulose fibers is purified from the small fraction of the polymer-aluminum mixture in a conical mill and two pressure sorting, cellulose fibers are ground, clean cellulose pulp is dissolved into fibers, the keratinized fibers of waste paper are split and combed in a disk mill, after which the cellulose pulp is sent to the headbox of the paper-making machine and fed onto the mesh of a rotating mesh drum, the cellulose pulp is dewatered and base paper for sanitary and hygienic products is formed.

The claimed method for producing base paper for sanitary and hygienic products from waste paper is carried out in several stages as follows (Fig. 1 shows a block diagram of the claimed method).

1. Stage of waste paper preparation.

In the preparatory and grinding department of the base paper production shop, waste paper is prepared for use in the technological process.

Bales of waste paper are fed to receiving table 1, where the bales are freed from binding materials and spacers. Next, the waste paper passes along a conveyor belt through bale openers. At this stage, the waste paper is loosened and further cleaned of dust and sand.

2. Stage of dissolution.

After passing through the first stage, the cleaned waste paper is fed via a conveyor belt into a screw hydropulper 2, pre-filled with water. As the screw of hydropulper 2 rotates, a vertical flow of water and waste paper is created. Due to the constant pressure of the pulp on the lower layers and the action of the water, the multilayer material is broken down into its individual raw components: recycled cellulose fiber, aluminum foil, and polyethylene.

3. Recycling stage.

Upon completion of pulping, the time of which depends on the density of the paper component of the waste paper, the percentage of non-paper inclusions, the presence of adhesives, the fraction size of the waste paper layers, and other factors, the resulting liquid pulp containing cellulose fibers and a fine polymer-aluminum mixture is fed through the pulper screen into separator 3 for grinding to a uniform density. At this stage, the liquid pulp, consisting of paper fibers, is separated from the polyaluminum mixture. A special feature of this invention is the setting of the separator blade gap at 0.02-0.05 mm, which enables the production of a uniform pulp with a predetermined concentration already at this stage. The liquid paper pulp, passing through the separator screen with a mesh diameter of 8 mm, enters the pulp refining tank, where it is continuously mixed to maintain a constant pulp concentration throughout the tank.

Uniform grinding of the pulp, maintaining the pulp concentration at set values thanks to a system of valves on the main pipelines, automated control of the pulp concentration by portioning the pulp and water in a set ratio, as well as stable pulp concentration and maintaining the grinding degree thanks to the mill fittings, make it possible to obtain durable, high-quality paper from recycled cellulose.

The coarse polymer-aluminum mixture, driven by the centrifugal force generated by separator screw 3, enters drum screen 4 for further cleaning of the foil and polyethylene layers from paper fibers. The cleaned and dried mixture is fed to stage 5 for pressing and baling, which is then sent to a warehouse for further distribution to other manufacturers.

4. Stage of paper pulp refining.

From the pulp tank 6, the paper pulp goes through several additional stages of cleaning and preparation.

Pumps feed the pulp to a conical mill 7, where metal inclusions (paper clips and staples) are precipitated during the initial grinding of the paper pulp. The inclusions leave the mill and are transferred to a vibrating table 8 as waste, which is subsequently disposed of. The pulp, freed of large inclusions, is fed to a pressure screen 9 and 10, where fine inclusions are removed. The inclusions formed during this stage are fed to a vibrating screen 11, where the waste is separated from the water. The separated waste is then disposed of on the vibrating screen 11.

Next, the paper pulp is pumped to the preparation stage and passes through disc mills 11 and 11-1. At this stage, the final pulp disintegration into fibers occurs, with the keratinized waste paper fibers split and combed to increase the surface area of the paper fibers and restore their paper-forming properties.

The degree of refinement of paper pulp prepared from MS-11V waste paper is 37-42 degrees SR, while the degree of refinement of paper pulp prepared from MS-7B waste paper is 32-37 degrees SR. Paper pulp obtained by repulping MS-11V waste paper has a higher degree of refinement. The quality characteristics of base paper produced from this raw material are quite high (Table 1).

5. Stage of paper web casting.

After the refining stage, the prepared paper pulp enters the prepared pulp tank 12 of the paper machine. The pulp, with a concentration of 0.12-0.20%, enters the headbox 13, where it is fed in a uniform flow onto the screen of a rotating screen drum. The screen dewaters the paper pulp; water, flowing through the mesh, leaves fibers on the screen, forming a paper web, which is pressed by couch roll 14 and transferred to synthetic felt 15. The felt transports the pulp to Yankee cylinder 16. Upon contact with the heated surface of the Yankee cylinder, the formed paper is intensively dried, wound onto reel rollers 17 and transferred to a warehouse as finished rolls of base paper for the production of sanitary and hygienic products.

The technology utilizes a closed-loop water supply system, where water is reused without being discharged into wastewater. Water circulates from pulper 2 through sump 18 and through recirculating water tank 19.

Table 1. Conditions for implementing the method and properties of the obtained base paper.

Item No. Name of raw materials Quality indicators of base paper Degree of grinding of the mass, ºШР Dry tensile strength, N Degree of purification of polyaluminium mixture Degree of purification of cellulose fibers Technological losses Dustiness Bulk 1 Waste paper grade MS-11V 37-42 2.4 95% 98% 6% No low 2 Waste paper grade MS-7B 32-37 1.3 - - 12% Yes high

Claims (1)

A method for producing base paper for sanitary and hygienic products from waste paper made from various materials, including splitting it, characterized in that before splitting, the waste paper is first freed from dressings and pads and loosened, then it is mixed with water and split into secondary cellulose fiber, aluminum foil and polyethylene, the dissolved cellulose mass is separated into a liquid mass with cellulose fibers, small and large polymer-aluminum mixtures, the liquid mass with cellulose fibers and the small polymer-aluminum mixture are fed to a separator for grinding to a uniform density, the large polymer-aluminum mixture is additionally purified from the remains of cellulose fibers, pressed, dried and bales of the polymer-aluminum mixture are formed, the liquid mass with cellulose fibers is purified from the small fraction of the polymer-aluminum mixture in a conical mill and two pressure sorters, The cellulose fibers are ground, the pure cellulose mass is dissolved into fibers, the keratinized fibers of the waste paper are split and combed in a disk mill, after which the cellulose mass is sent to the headbox of the paper-making machine and fed onto the mesh of a rotating mesh drum, the cellulose mass is dewatered and base paper for sanitary and hygienic products is formed.