The requirements of high-speed paper bowl forming machines for raw materials (paper bowl base paper and PE-coated paper), as well as the impact of raw material characteristics on forming quality, can be analyzed from three dimensions: functionality, adaptability, and stability. Here are the details:
1. Core Requirements of High-Speed Paper Bowl Forming Machines for Raw Materials
1.1 Requirements for Paper Bowl Base Paper
Strength Indicators:
Tensile strength: It must meet the stretching and curling demands during high-speed conveying and forming to prevent breakage.
Stiffness: It should ensure the base paper is not easily deformed during processes such as feeding and curling-especially critical for maintaining shape stability when forming the bowl body.
Burst resistance: It needs to resist paper layer damage caused by extrusion and folding during forming.
Physical Stability:
Moisture content: It must be controlled between 6% and 8% (excessive moisture makes the base paper soft and dimensionally unstable; insufficient moisture increases brittleness and cracking risk).
Fiber uniformity: The paper surface must be free of wrinkles, holes, and impurities to avoid bulging or uneven thickness in the formed bowl body.
Dimensional Accuracy:
The width and length deviations of the base paper roll must be ≤±0.5mm to ensure compatibility with the equipment's feeding mechanism, preventing positioning errors caused by dimensional discrepancies.
1.2 Requirements for PE-Coated Paper
Coating Layer Characteristics:
Coating material: Food-grade polyethylene (PE) must be used, complying with food safety standards such as GB 4806.7. It should be odorless and acid- and alkali-resistant (to prevent harmful substances from leaching when holding food).
Coating thickness: It should be adjusted based on usage (30–50μm for cold-drink bowls; 50–80μm for hot-drink bowls). Thickness uniformity deviation must be ≤5μm (excessively thin coatings risk leakage, while overly thick ones increase costs and hinder forming).
Composite Strength:
The peel strength between the paper and PE layer must be ≥0.3N/15mm to prevent delamination during forming processes (e.g., heat-press bonding, folding)-particularly at the connection between the bowl bottom and bowl body.
Thermal Stability:
The PE layer must have a stable melting point (typically 105–130°C). It should melt uniformly and solidify quickly during heat sealing, matching the equipment's heat-sealing temperature (usually 150–200°C).
2. Specific Impacts of Raw Material Characteristics on Forming Quality
2.1 Impact of Base Paper Thickness
On bonding firmness:
Excessively thick: The base paper becomes overly rigid, making it difficult to fit tightly when bonding the bowl body to the bottom. This may cause loose contact at the bonding surface, leading to weak adhesion or detachment-especially problematic in high-speed production, where short bonding times make it harder to compact thick paper.
Excessively thin: While thin paper fits easily, it has poor tensile resistance. After bonding, external forces (e.g., expansion when holding food) may tear it, causing cracks at the bonded joints.
On bowl rim flatness:
Uneven thickness: Localized thick areas of the base paper create uneven force during rim curling, resulting in skewed curls and height differences (a deviation >0.3mm is considered unqualified).
Excessively thick: The paper is difficult to curl uniformly during the curling process, prone to wrinkles or "edge warping," which impairs the bowl rim's sealing ability (e.g., poor fit when a lid is added).
2.2 Impact of PE Coating Uniformity
On bonding firmness:
Uneven coating (local thinness or gaps): During heat sealing, insufficient melting of the PE layer prevents the formation of a complete sealing layer on the bonding surface, reducing bonding strength and even causing leakage-especially when holding liquids.
Local over-thickness: Melted PE in thick areas has poor fluidity, potentially forming "accumulations" at the bonding point. After cooling, hard lumps form, leading to uneven stress distribution on the bonding surface, which may crack at the thickened areas over time.
On bowl rim flatness:
Significant coating thickness deviations: Thicker PE areas dissipate heat slowly during curling, causing greater post-cooling shrinkage than other areas and resulting in local indentations or protrusions on the bowl rim. Conversely, thin areas may lack heat resistance, getting scorched during curling and damaging flatness.
2.3 Other Key Impacts (Extended Notes)
Base paper fiber uniformity: Uneven fiber distribution leads to inconsistent shrinkage of the base paper, which may distort the formed bowl body and indirectly affect the concentricity of the bowl rim and bottom.
PE coating heat resistance: If the PE layer lacks heat resistance (e.g., using low-melting-point PE for hot-drink bowls), it will soften when holding high-temperature liquids, causing the bowl to deform or even the bonding to fail.
Zhejiang Xinxinli Machinery Co., Ltd
Tel: +86-577-65577123
Fax: +86-577-65577123
Mob: +8618657789284
Email: monica@aeast.com
Add: No.9, Yuandong Road, Feiyun Street, Ruian City, Zhejiang Province, China
