The Production Process of Pulp Molding

1.Introduction

Pulp molding is a sustainable manufacturing process and an eco-friendly packaging solution. This technology includes several different production processes, each with unique applications and advantages. The following is a detailed introduction to the key pulp molding production processes:

1.1 Dry Pressing Process

The dry pressing process is one of the traditional methods in pulp molding production.Most of the raw materials are recycled waste paper, old corrugated boxes, old newspapers and magazines, etc.This technique involves several stages: forming, drying and trimming. Initially, pulp is molded into a wet pulp product using a forming machine. The wet pulp is then transferred to an external drying system (out-of-mold drying) before undergoing trimming. This method is relatively simple and energy-efficient, and the products produced by this process are thick and have good shock and compression resistance,making it ideal for producing items like egg trays, fruit trays, and general industrial packaging products.

Key Features:

• Separate Stages：Shaping, drying and trimming are separate steps
• Energy Efficiency: Lower energy consumption compared to more advanced methods.

1.2 Wet Pressing Process

The raw materials used in the pulp molding wet pressing production process are mainly commercial pulp boards, including sugar cane pulp, bamboo pulp, reed pulp, etc. After being crushed and slurried, the pulp is injected into the molding mold through a pipeline. Excess moisture is removed by vacuum absorption, forming a wet slurry which is then immediately transferred to the hot-press shaping mold for rapid extrusion and drying. This wet pressing process is highly efficient, allowing for immediate transfer and finalization after forming, resulting in fast production speeds. The degradable products produced by this process have smooth and delicate surfaces, are aesthetically pleasing, and have thinner packaging walls, higher density, and save volume. This process is mainly used for producing high-precision tableware, electronic packaging, and premium industrial packaging products.If you want a more intuitive understanding, you can watch the video on our homepage, which takes the wet pressing process as an example.

Key Features:

• Integrated Process: All processes can be completed coherently.
• High Efficiency: Faster production with excellent quality output.

1.3 Semi-Dry Pressing Process

The semi-dry pressing process strikes a balance between the dry and wet pressing methods. In this technique, the pulp product undergoes partial drying through air drying, sun drying, or other methods to maintain a moisture content of around 35%. Subsequently, in-mold drying or shaping is performed to achieve a product quality that is intermediate between dry and wet pressing methods, while significantly reducing energy consumption compared to the wet pressing process.Suitable for products requiring moderate precision and quality such as mid-range food packaging, protective packaging for fragile goods, and medium-quality industrial packaging.

Key Features:

• Partial Drying: Reduces moisture content to about 35% before final drying or shaping.
• Energy Efficient: Lower energy consumption compared to wet pressing.

1.4 Direct Pressing Process

The direct pressing process represents a significant innovation in pulp molding production. Unlike traditional methods that involve re-pulping and molding wet pulp, this technique utilizes raw material pulp sheets or boards without the addition of water. The raw materials are directly processed through hot-press molding equipment after being sprayed with latex or other additives as needed. This dry method eliminates the need for extensive drying stages, resulting in substantial energy savings.Ideal for producing energy-efficient pulp molding products such as high-end packaging for electronics, premium gift packaging, and specialty industrial components.

Key Features:

• Dry Method: Utilizes dry pulp sheets or boards without re-pulping.
• Energy Saving: Reduces energy consumption by eliminating traditional drying stages.

2.Comparison Table of Four Production Processes

3.Conclusion

The evolution of pulp molding production processes reflects the industry’s commitment to sustainability, efficiency, and high-quality output. From the traditional dry pressing process to the innovative direct pressing technique, each method offers unique advantages tailored to specific product requirements. As technology continues to advance, we can expect further innovations that will drive the pulp molding industry towards greater sustainability and efficiency.

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