1. Pulp Preparation: The process begins with the collection of recycled paper, which is then shredded into small fibers.
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2. Slurry Formation: These fibers are mixed with water to create a pulp slurry, which serves as the raw material for molding.
3. Molding: The pulp slurry is poured into molds of desired shapes and sizes. These molds can be customized according to specific packaging needs.
4. Drying: Once molded, the excess water is removed from the pulp using heat and pressure, resulting in solidified packaging material.
5. Finishing: The dried pulp packaging products undergo finishing processes such as trimming and labeling before being ready for use.
The appeal of the molded pulp machine lies in its numerous advantages, making it an attractive option for businesses aiming to adopt sustainable packaging practices:
1. Environmentally Friendly: As the molded pulp machine utilizes recycled paper as its primary raw material, it significantly reduces the demand for virgin resources and minimizes waste sent to landfills.
2. Biodegradable and Compostable: Packaging products produced by the molded pulp machine are inherently biodegradable and compostable, offering a sustainable end-of-life solution.
3. Versatility: The flexibility of the molded pulp machine allows for the production of a wide range of packaging products, including trays, containers, and protective cushioning, catering to diverse industry needs.
4. Cost-Effective: While initial investments may be required for setup, the long-term cost-effectiveness of the molded pulp machine becomes evident through reduced material costs and potential savings on waste management.
5. Consumer Appeal: In an era where consumers are increasingly eco-conscious, products packaged in molded pulp are perceived favorably, contributing to brand reputation and customer loyalty.
With the advancement of the global economy and technology, green packaging has gradually become a shared societal consensus and a major trend in the development of the packaging industry. Modern packaging typically uses materials such as paper, plastic, glass, ceramics, and metal. However, due to the low cost, ease of processing, and wide availability of raw materials, paper and plastic are the most commonly used in daily life. That said, plastic is not biodegradable and can cause environmental pollution, making paper the most promising green packaging material. In the following, we will discuss the production process of molded paper pulp packaging as well as its advantages and disadvantages.
The production process of molded paper pulp packaging mainly includes the following steps: pulp preparation, forming, drying, shaping, and packaging.
Pulp making: It refers to the process of breaking down pulp boards or waste paper into fiber slurry by using a hydraulic pulper, followed by screening to purify the slurry. The necessary equipment includes a hydraulic pulper, belt conveyor, pulp pump, pulp beater, and pulp tanks. For smaller-scale production lines, using just a hydraulic pulper and pulp tank can also meet production requirements.
In the pulp making process, it is essential to strictly control the beating degree of the slurry. If the beating degree is too high, it will lead to difficulties in dewatering during forming, and the product may shrink or deform after drying. On the other hand, if the beating degree is too low, the stiffness and compressive strength of the product will be significantly reduced. Therefore, the beating degree should be determined based on the type of pulp used, the pulp ratio, and the overall pulp quantity.
Pulp blending: It refers to the process of adding fillers, pigments, and functional additives—such as water- and oil-resistant agents—into the treated pulp to prepare slurry that meets the quality requirements of the final product. To ensure continuous production and product uniformity, it is essential to maintain proper slurry levels in the storage and blending tanks. Fillers, water, and additives must be added at fixed intervals and in precise quantities.
Functional additives such as water resistant and oil resistant agents can be added to the paper pulp as needed. Currently, the main water-repellent agents used in molded paper pulp packaging include rosin, ferric sulfate, and cationic starch.
Product forming refers to shaping the prepared fiber slurry by vacuum suction onto a mold fitted with a metal mesh, while simultaneously removing a large amount of water. The workflow is as follows:
1. The male mold moves down into the slurry tank
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2. Vacuum suction draws the slurry onto the male mold
3. The male mold lifts up
4. The male and female molds close together with pressure, meanwhile dewatering
5. The female mold lifts and the formed product is released
This process shapes the product while significantly reducing its moisture content in preparation for drying. The production equipment includes a pulp molding machine, vacuum pump system, water tank, etc.
During the forming process, the thickness of the product can be controlled by adjusting the slurry suction time. In theory, since vacuum suction applies uniform pressure across all areas of the mold, the resulting product should have an even thickness. However, due to factors such as slurry flow rate and gravity during the suction process, variations in thickness may still occur.
Due to the resistance of the fiber layer, products formed through vacuum suction only reach a dryness level of 20% to 30%. However, the final dryness required for molded pulp packaging must exceed 90%. Therefore, semi-dry products need to undergo heating and dehydration in specialized drying equipment to meet the standards for hardness, wear resistance, and compressive strength.
After forming and drying, the molded paper pulp packaging may undergo varying degrees of deformation, and its surface may have burrs or marks left by the mold mesh. When customers have high appearance requirements, the products must go through trimming, reshaping, alignment, and surface pressing to ensure smooth and even inner and outer surfaces.
In addition, based on customer needs, text and patterns can be printed on the packaging surface, and creases can be pressed to facilitate lid folding. During the reshaping process, hot pressing machines and printers are used. The typical hot pressing temperature is controlled between 150–180°C, and although adjustable, it should not be set below 135°C.
Sterilization is a crucial step in the production of food packaging. Currently, there are three main methods of sterilization: ozone sterilization, ultraviolet (UV) light sterilization, and high-temperature sterilization. After sterilization, the finished products undergo quality inspection, followed by collection, stacking, counting, and packaging using an automatic packing machine according to the required quantity—completing the entire production process.
1. The raw materials used in molded pulp packaging are waste paper and various types of fibrous materials, which are widely available and easy to collect. They pose no obstacles to environmental protection or recycling, making them especially advantageous for export-oriented products.
2. Molded pulp packaging has a wide range of applications and can essentially replace any packaging that uses foam as an inner lining. It is stackable and requires minimal storage space, which helps reduce both shipping and warehousing costs.
3. It has good anti-static properties, which provide effective protection for electronic products and household appliances.
4. Molded pulp packaging offers good water and air permeability, which helps achieve effective anti-corrosion performance.
1. The production quality of molded pulp packaging is easily affected by various manufacturing factors.
① If the raw material quality is unstable, the shrinkage rate after drying may not align with the original design specifications. Additionally, improper slurry formulation will lead to a high product defect or breakage rate.
② Using the same set of molds on different models of forming machines can result in variations between products, which may lead to a higher defect rate during the reshaping process.
③ Improper control of humidity during the drying process can lead to a high defect rate. If the product deforms too severely after drying, it will affect the overall product quality.
2. Molded pulp packaging has relatively low structural strength and cushioning performance.
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