Can you make pulp with cardboard

Table of Contents

Yes, you can make pulp from cardboard by soaking, shredding, and processing it into fine fibers, achieving over 95% fiber recovery.

Preparation of Cardboard for Pulp Making

The process of creating a pulp from cardboard is a multistage procedure that requires careful preparation. The two fundamental steps in this phase are Sorting and Cleaning Cardboard and Cutting and Shredding Techniques. In each of them, paying attention to detail is essential to ensure the quality of the final product.

Sorting and Cleaning Cardboard

The first operation in preparing the cardboard is to sort and clean the material. In this process, any components preventing the pulping should be removed, such as plastics, metals, or residues of foods . The sorting employs the distinction between types of cardboard and its quality. Junk of this material comes in two main forms: corrugated cardboard, used primarily for boxes containing goods for shipping, and paperboard, employed for boxes with various cereals and other types of food.

Next, the sorting station is the process of cleaning. At this stage, workers remove any tape, staple, or label that was attached to the cardboard. This is also essential because all those materials can prevent the pulping process . Research shows that removing non-paper elements remains one of the most common ways to improve pulp quality by 30%. To prepare for the next step, designed to break it down, the cleaned cardboard needs to be soaked in water.

Cutting and Shredding Techniques

Once the cardboard is sorted and cleaned, it is brought for the last preparation phase designed for it: cutting and shredding. The object is to break it down into smaller pieces where the increasing surface is critical. Cutting to which size the cardboard is also matters. The optimal solution for breaking it down effectively throughout pulping is to shred the cardboard into pieces with sides not larger than 5 cm, preferably square-shaped . The tools to perform this operation are a paddle cutter or wolverine .

Shredding can be made by industrial machines or large scissors. The difference also affects the absorbing power: the more these devices can shred, the faster the operation goes. If bought as an industrial shredder, the machine’s capacity can be dozens of kW, consuming, for instance, 50 kW and in return tearing several tons of cardboard in an hour . By comparison, a smaller shredder will consume about three times less power and allow to draw a dozen kilograms of the material at once. Another factor is also the swiftness of the shredder. The faster it shreds, the less time-consuming is the whole pulping process – yet, the more power it consumes in return. Therefore, as it can be seen, it is vital to consider a few factors to correctively adjust the power consumption to the time-effectiveness with which the input material is shredded.


The Pulp Making Process

The first critical step in the recycling process is when cardboard is turned into pulp. The process includes Soaking and Breaking Down Cardboard followed by Mechanical vs. Chemical Pulping Methods to create the final product.

Soaking and Breaking Down Cardboard

In the pulp making process, the first step involves soaking the prepped cardboard pieces in water. Soaking refers to the process of immersing cardboard chunks in water to soften the material for easier fiber separation. The length of soaking time has a significant effect on the efficiency of pulping; normally, a period of 24 hours is enough to soften the cardboard material. The water temperature is a major consideration at this stage, for it can reduce the soaking time when the water is warm by up to 50%.

The second step involves breaking down the cardboard material into its fibrous components. Breaking down of the cardboard is usually done by a combination of mechanical and chemical methods used to help in breaking down the cardboard bonds . The aim of the second step is to create a slurry of fibers that can be further pulped to create a pulp. An efficient soaking and breaking down of cardboard are characterized by the number of cards broken fully into its constituent fibers . The recommended percentage is more than 95% of the original material so soaked and broken down.

Mechanical vs. Chemical Pulping Methods

Pulping is the process of turning the slurry of the soaked and broken-down unrefined material into pulp. In most cases, the two pulping methods applied at the pulping phase include Mechanical pulping and Chemical pulping methods . The two have characteristics, costs, and qualities that make it a requisite to apply and assess before the final pulp is created.

Mechanical pulping is the method that involves grinding the material up to separate the fibers. Its major disadvantage is the energy consumption as the grinders use approximately 30 kWh per ton of pulp. However, the advantage it has over the other method is that it saves most of the wood’s original lignin . The typical efficiency of mechanical pulping is approximately 95%, with most of the material is retained owing to the lignin presence. It will, however, make paper produced turn yellow and weaken quickly . As such, it is used to produce short term products like newspapers and cardboards. Chemical pulping, on the other hand, is method uses chemicals to dissolve the lignin . Though having a lower efficiency ratio, the technology allows for the creation of durable papers. It consumes less energy, approximately 10-15 kWh, though the cost of creating bleaching chemicals is relatively high . The most common form of chemical pulping is the Kraft process, and it allows all the chemicals to be saved. Overall, to choose between mechanical and chemical pulping, evaluations like prospective end product quality. The mechanical process is applied for the production of low-quality paper that is cost-effective to sustain, and the chemical is better for high-valued paper because of the stronger paper it produces.


Pulp Processing and Refinement

The processes of Screening and Cleaning the Pulp and Enhancing Pulp Quality through Refining are completed after the cardboard has been turned into a basic pulp. These processes are necessary steps in creating a high-quality, usable pulp. Each of these processes is detailed below.

Screening and Cleaning the Pulp

Screening involves running the pulp through “screens”, which are only able to allow the pulp’s fibers to pass through. This separates the fibers from commingled materials such as dirt or plastic bits, which could not be removed during earlier cleaning processes. Cleaning the pulp, on the other hand, involves eliminating smaller particles of sand, dust, or left-over plastic from the pulp. There are many different methods of screening and cleaning pulp, with capacities of up to 1,000 liters of pulp screened per minute. In most cases, the equipment has slots that are small enough to trap contaminants but large enough to let the fibers pass. Cleaning the pulp is typically done with centrifugal cleaners, which are cones that spin the pulp at high rates. This causes the heavier particles to slide out of the pulp and slowly moves them to the edge of the cone where they are expelled as contaminant deposits. These cleaners are able to remove up to 99% of materials that are not the pulp fibers, making them a very effective tool in refining pulp . The high quality of the pulp, at this point, makes it ideal for producing standard specifications for printing paper.

Enhancing Pulp Quality through Refining

Refining pulp serves to improve the bond between its fibers, which will determine the overall texture and strength of the paper . This is achieved by physically manipulating the fibers, which causes them to fibrillate. This means the fibers will be broken into fine splinters, which will increase the fibers’ surface and their ability to bond. Different refining equipment uses different amounts of energy, with refining needing between 15-30 kWh to refine one ton of pulp. The level of refining necessary for each type of paper also changes. Light refining is used for papers that do not need strength, and intensive refining is used in creating the strong papers. The differences in strength are significant – moderately refined pulp will have a strength of around 30 Nm/g, while intensively refined pulp will have a strength of 45 Nm/g. Thus, the refining process is able to guarantee the bond quality necessary for high-end writing paper or even currency paper.


From Pulp to Product

Making a wide array of paper and paper-based products from pulp involve Molding and Shaping Pulp into Forms and Drying and Finishing Techniques. These aspects are key to the quality, durability, and appearance of the final products.

Molding and Shaping Pulp into Forms

Molding simply refers to the act of depositing the pulp onto screening surfaces or into molds that determine the forms the pulps will take. This stage is significant in the production of a wide array of products, whether they are cautionary paper to complex and three-dimensionally shaped packaging. The type and texture of the mold used determines the thickness and density of the products. For instance, fine-mesh molds result in high-quality products with a smooth surface, which is perfect for writing paper. Conversely, coarser molds are used to make hard paper, which is commonly used in packaging. The shaping process merges the pulps and presses them to eliminate and excess water as well as compact the forms to ensure they are firm and durable. The pressing may be done using simple mechanical presses, which apply up to 10 tons of pressure, or hydraulic presses, which apply much higher pressures . The pressure is also maintained for different durations, enhancing the density and strength of the paper.

Drying and Finishing Techniques

Drying refers to the process of eliminating the remaining moisture in the already shaped product. This helps in setting the products in the desired form while enhancing its strength. Different products are left to dry in open air or in drying ovens or passes through heated rollers to enhance their dexterity. Press drying is efficient as it may reduce drying time from a period of days to a few hours or even less, speeding up the production processes. However, the speed must be regulated as higher temperatures warp and weaken the paper. The finishing process, just as in the case of normal paper, is used to improve the appearance or characteristics of the product. Generally, calendaring is the most significant process, which involves running the product through heated rolling surfaces, glossing the paper. Fine paper, mainly for magazines and products, undergoes calendaring, which glosses them to ease the feeding process in high-quality printers and improve image sharpness and clarity. On the other hand, packaging and other papers undergo coating, which involves adding a thin layer of materials to the surface. The nature of the material improves certain aspect or characteristics of the paper. For instance, paper for inkjet printings is coated to enhance the absorption of inks and interaction for sharp and coherent images. In turn, packaging materials are coated with light turpentine and grease-resistant spices to preserve the contents. The two families of techniques regulate the form and function of the products, ensuring they attain the favorable qualities required and the intended characteristics and characteristics.

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