We offer a clear and concise look into Pulp Molding Machine, helping readers grasp the essentials with ease.
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Molded pulp (also known as molded fiber) packaging is made from a variety of fibrous materials such as recycled paper, cardboard offcuts or natural fibers (sugarcane bagasse, bamboo, wheat straw). The raw materials help determine the color, surface texture and physical properties of the packaging (more info).
Pulp packaging is made from a series of steps. First, the raw materials (cardboard / newspaper / natural fibers) are blended with water to make a pulp slurry. A mesh forming tool is lowered into the pulp slurry tank. A vacuum pulls the slurry through the mesh tool until the desired thickness is achieved. The wet parts are released from the mesh tools and dried. The dried parts are bumpy and deformed. To smooth the surfaces, the parts are pressed by heated metal tools. Debossed logos or artwork can also be applied at this stage. Finally, the edges are trimmed and any holes or windows are die cut (more info).
Unlike traditional folded cardboard boxes, molded pulp packaging has rounded corners and complex three dimensional shapes. When the pulp parts are formed, they need to release from the forming and pressing tools — so sharp 90 degree angles are not feasible. Instead, pulp packaging is designed to have 5-10 degree draft angles and corner radii.
We are living in a world where the environmental footprint of packaging is important more than ever. Luckily, molded pulp has emerged as a promising solution. Yet, understanding its full scope requires a balanced examination of its environmental impact, production processes, and the economic implications of switching to this material. Let us delve into an honest, broad analysis of molded pulp packaging.
What is molded packaging? Molded pulp, also known as molded fiber, is a packaging material made primarily from recycled paperboard and newsprint. In short, it is designed through a process that involves hydrating fibers to a pulp, molding them into specific shapes, and then drying them. To be more precise, molded packaging involves the creation of a pulp slurry by combining recycled paper and water. This slurry is then shaped into various forms using techniques such as vacuum forming or pressure forming. Once molded, the pulp undergoes a drying process to produce sturdy, lightweight packaging that is both biodegradable and recyclable. This eco-friendly production method not only minimizes waste but also significantly reduces the environmental impact compared to conventional plastic packaging. The molded pulp material is often praised for being environmentally friendly since it is made from renewable resources and is biodegradable and recyclable. Learn more about the process.
The production of molded pulp is praised for its low environmental impact, as it often uses recycled materials. Besides this, less water and energy are used compared to traditional plastic packaging production. It also generates fewer greenhouse gas emissions and results in products that can be recycled or composted after use. Thus, it contributes to a closed-loop cycle that benefits the environment.
However, it is not without environmental concerns. The production process for molding can consume lots of energy and pulp can lead to chemical emissions, contributing to air and water pollution. These emissions may include sulfur compounds and nitrogen oxides, which are harmful greenhouse gases (EPE Global).The industry also faces criticism for deforestation if virgin fiber is used, contributing to habitat loss and biodiversity decline.
While the manufacturing of molded pulp packaging employs a straightforward process of mixing water with paper fibers, there are complexities involved. This includes the need for chemical pulping to remove the lignin and increase strength. A step that can cause pollution due to the release of chemical emissions. Moreover, the pulp and paper industry is a significant industrial source of pollution to air, water, and land resources. Another concern is the potential release of dioxins, particularly when chemical bleaching processes are used. Dioxins are highly toxic and pose risks to human health and the environment, contributing to the pollution footprint of the molded pulp industry.
From a physical standpoint, molded pulp packaging's sensitivity to moisture can be a drawback. Exposure to wet conditions can compromise its structural integrity, making it unsuitable for some products or environments. This can only be solved if they are treated with additional protective coatings, which can increase costs. Besides this, its design flexibility is limited compared to other materials like plastic, which can be more easily shaped into intricate designs. Customizing molded pulp packaging to achieve specific aesthetic goals or functional requirements may also result in higher production costs.
The switch to molded pulp can entail higher upfront costs due to the investment in manufacturing equipment and the development of custom molds. For small-scale production, these costs can be prohibitive, impacting on the overall cost-effectiveness of the material. Market adoption also plays a significant role in determining the viability of molded pulp. Consumer preferences are shifting towards environmentally friendly options, yet hesitancy remains among some retailers and manufacturers. This is mainly due to concerns over cost, durability, and the need for supply chain adjustments.
Despite its recyclability, the effectiveness of recycling molded pulp varies by location, depending on local recycling facilities' capabilities. For instance, in some regions, recycling programs may not be equipped to process molded pulp, leading to inconsistent recycling rates. Composting, although a potential end-of-life option, requires specific conditions and infrastructure. Something which may not be widely available, limiting the material's end-of-life benefits.
Looking at the broader picture, while molded pulp packaging is a step in the right direction for sustainability, it is not a perfect solution. Its advantages in sustainability must be weighed against the challenges in manufacturing, economic costs, design limitations, and end-of-life processing. Companies considering the transition to molded pulp must carefully consider these factors and how they align with their operational capabilities and sustainability goals. Exploring various packaging materials initially would also be beneficial, enabling us to determine which type best meets our needs.
Innovation in materials and manufacturing processes may address some of the current limitations of molded pulp packaging. Ongoing research into alternative fiber sources, more efficient production techniques, and advancements in recycling and composting infrastructure could enhance the attractiveness of molded pulp as a packaging material.
As we strive for more sustainable packaging solutions, it is clear that molded pulp will continue to play a significant role. Yet its adoption must be part of a larger strategy that considers the full pros and cons. If you need advice on whether pulp packaging would be a suitable option for your project, feel free to contact us!
Thanks for reading! As you consider your next move, keep in mind the insights shared here about Molded Pulp Equipment，. Staying informed is the first step toward making smarter, more strategic investments.
Pulp molding is a three-dimensional papermaking technology, which means that a certain concentration of pulp is added with appropriate chemical additives in the molding machine to uniformly distribute the fibers on the surface of the mold through vacuum or pressure, so as to make a wet paper mold blank, which is then further dehydrated. Mold, the production technology of drying and shaping the product into a pulp molded product. Products produced from waste paper with different compositions have different properties.
Therefore, different waste paper or several waste papers can be used in combination according to the purpose of the product to obtain better economic benefits and performance. Pulp molded products can be designed to improve their structure, and various components of materials or surfaces can be specially treated during production to achieve the performance and characteristics required for a certain item or under certain conditions. In addition, the characteristics of the paper molds obtained by different processing methods are different, so changing the processing method or process can improve the performance of the paper mold.
01 Advantage
It has four major advantages: the raw material is waste paper, including board paper, waste carton paper, waste white edge paper, etc., with a wide range of sources; its production process is completed by pulping, adsorption molding, drying and shaping, and other processes, which are not harmful to the environment; It can be recycled and reused; the volume is smaller than foamed plastic, it can be overlapped, and the transportation is convenient. Pulp molding is not only used for lunch boxes and tableware, but also for industrial cushioning packaging. It is currently developing very rapidly.
02 Process flow
pulp paper+water➡milling in the mixing pail➡add related material in mixing pail➡Backflow slurry tank➡product forming➡drying➡Sterilize➡packing
Main process
Pulping
1) Raw materials
a.Fiber that meets hygiene requirements➡Food packaging
b.Waste paper, cardboard➡General packaging
2) Process
Sorting → Breaking → Screening → Refining → Desanding
Blending
The pulping process includes the addition of fillers, pigments, water and oil repellents and other chemical additives, and the pH value and pulp concentration need to be adjusted.
1) Additives
add anti-water,anti-oil material or other material
2) Mixing pulp: pH value 4.5～5.0 Pulp concentration: 1%～2%
forming
The molding process of the pulp molded product is the deposition and filtration dehydration process of the fibers in the pulp on the forming wire mold. According to its molding method, it is divided into the following three types:
Link to ISTE Automation
1) Vacuum forming method
principle:
The forming mold has a porous structure with a certain mesh forming net attached to the surface. Through vacuum suction, a vacuum is formed in the cavity of the forming mold, the fibers in the pulp are deposited and attached to the surface of the forming mesh, and a large amount of water is taken away during the vacuum suction.
2) Compressed air molding method
principle:
The compressed air molding method is the opposite of the vacuum molding method. Instead of using vacuum suction, compressed air is used as a filter power to accelerate the deposition and dehydration process of pulp fibers on the mesh mold.
3) Extrusion method
principle:
A quantitative amount of pulp is injected into the forming cavity, and the upper forming mold is squeezed downward under pneumatic or hydraulic action, so that the pulp is formed on the net membrane in the forming cavity in a sealed state, and water is discharged from the lower end of the net mold.
press
1) Function:
①Remove most of the moisture from the paper mold.
②The product is further compacted to improve the bonding force between the fibers and increase the strength of the wet paper mold, eliminate the net marks during molding and improve the density and smoothness of the product.
2) Pressing method: ①cold pressing ②hot pressing
dry
After molding and pressing, the dryness of the molded pulp product reaches about 40%, and about 98% of the water has been removed. The excess water needs to be removed by drying, so that the dryness of the product reaches about 97% of the atmospheric balance. Dryness. The drying methods are:
Drying with mold: products are smooth, dense and precise in size and shape
Demoulding and drying: product shrinkage rate is large, dimensional accuracy is not high
Plastic surgery
The hot pressing method is used to correct the shape of the dried product to make it meet the quality requirements.
Molded dry products do not need to be reshaped.
The mold-relieved and dried product can improve the shape and surface quality of the product due to the shrinkage of the paper mold and the change of the geometric size during the drying process.
Package
After the dried or shaped products undergo quality inspection, they are collected, sorted, stacked, counted, and packaged according to the required quantity to complete the entire production process of the pulp molded product.
03 Causes and countermeasures of waste
Paper mold packaging products are environmentally friendly products that have emerged in recent years. Its main production processes include: beating process, forming process, drying process, and hot pressing and shaping process. In these four major processes, the waste generated by the hot pressing and shaping process accounts for about 80% of the total waste of the entire production line. In response to this phenomenon, talk about the causes and countermeasures of waste products.
1) The surface of the hot-pressing plastic mold made is not smooth and there are many blisters, which affects the quality of the product. Attention should be paid to the purchase of high-quality aluminum materials for sanding, and the finished molds should be smoothed with fine sandpaper.
2) The processed mold has uneven clamping distance between the upper and lower molds, and the product is easy to be scraped when the mold is shaped. The mold should be processed in strict accordance with the specified scale, and the clamping distance between the upper mold and the lower mold should be equal.
3) When installing the mold on the shaping machine, the upper and lower molds are not parallel, causing serious mold rubbing. There should be a dedicated person to install the mold, and it is best to use an instrument to measure whether the upper and lower molds are parallel.
4) The quality of the purchased raw materials is unstable, the shrinkage rate of the product after drying does not match the original juice process, and the scrap rate is high when shaping. It is better to buy corrugated paper edges, gray cardboard and old newspapers cut by a designated carton factory.
5) Improper mixing ratio of beating slurry results in high product damage rate. Different slurry formulas should be selected according to the different paper mold structures.
6) The same set of water molds are used to produce products on different models of molding machines, and there are certain differences between the productions, which leads to an increase in the scrap rate during the subsequent process of reshaping. The water mold should be fixed as far as possible to produce products on the same type of molding machine.
7) The drying product deforms greatly, which affects the overall quality. It should be noted that when people release wet products, they should be careful and grasp the angle of the discharge of different products, and control the drying curve according to different products.
8) The humidity of the molded wet product is not well controlled during drying, resulting in a high rate of plastic waste. The best drying temperature for different products should be mastered, and the humidity of the dried products should generally be 15-18%.
9) A large backlog of products after drying, air-drying for a long time, the product has low moisture content, excessive shrinkage, and high rejection rate during shaping. A long-term backlog of dried products should be avoided, and moisture regain control should be carried out on drier products before reshaping.
10) Insufficient operation experience of shaping workers, inaccurate shaping techniques, and high rejection rate. It is necessary to strengthen business training, continuously improve its work level, and adopt different methods of pressing, pressing, pinching, and pulling on different products to improve product quality.
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