Coated Paper Sack for Rainproof Deaeration
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Solution Overview
Problem
Paper sacks used for storing powdery materials like cement face challenges in maintaining strength, preventing moisture contamination, and ensuring efficient deaeration, while also being cost-effective and rainproof.
Innovation Solution
A coated paper is developed for the outer ply of the sack, featuring a hydrophobic-sized paper layer with a pre-coating and barrier coating, comprising binder, inorganic filler, clay, and synthetic rubber, which provides strength, moisture resistance, and allows for effective deaeration without the need for a plastic film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic film (free film) is used as moisture barrier, then moisture resistance is improved, but deaeration capability deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the barrier layer by using a multi-layer coating structure with hydrophobic sizing agents and specific polymer combinations (PVDC, EVOH) that provide moisture barrier properties while maintaining controlled permeability to air for deaeration
Solution Approach 2:
The invention uses composite material structure with multiple coating layers including hydrophobic size, PVDC layer, and EVOH layer on kraft paper, combining different material properties to achieve both moisture resistance and deaeration capability simultaneously
2Productivity
If paper porosity is increased to improve deaeration, then air permeability is improved, but strength deteriorates
Solution Approach 1:
The patent applies parameter changes by using hydrophobic sizing agents (rosin, AKD, ASA) that modify the paper's surface properties and internal structure, allowing air permeability to be maintained or improved while significantly increasing strength and water resistance
Solution Approach 2:
The invention utilizes porous kraft paper as the base material and enhances it with coating layers that maintain the porous structure for deaeration while adding strength through the composite coating system with multiple functional layers
3Strength
If multiple paper walls (plies) are used to increase strength, then tensile strength is improved, but device complexity increases
Solution Approach 1:
The patent applies composite materials principle by creating a multi-layer coated paper structure (kraft paper base with multiple functional coating layers) that provides the strength of multiple plies in a single integrated layer, simplifying the overall sack construction
Solution Approach 2:
The invention merges multiple functions (strength provision, moisture barrier, grease resistance, deaeration) into a single coated paper structure, eliminating the need for separate plastic film layers and reducing overall construction complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coated paper sack achieves high strength, efficient deaeration, and rain resistance, ensuring the integrity of the contents during storage and handling, while reducing costs by minimizing the use of expensive barrier materials.
Implementation Method 1
a paper layer that is internal-sized with at least one hydrophobic size
Implementation Method 2
the barrier coating layer comprises clay and synthetic rubber... which provides strength, moisture resistance
Data Source
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Figure 2
AI summary
The present disclosure provides a multi-ply sack comprising an inner paper ply and an outer paper ply, wherein: the outer paper ply comprises a paper layer that is sized with at least one hydrophobic size; the outside of the sized paper layer is provided with a pre-coating layer and a barrier coating layer; the pre-coating layer comprises binder and inorganic filler in a dry weight ratio of between 10:100 and 50:100; the Gurley porosity according to ISO 5636-5 of the inner paper ply is less than 10 s; and the sack is configured to allow air to escape from an interspace between the inner paper ply and the outer paper ply during filling of the sack.