Starch Viscosity Control for Molded Body Surface Smoothness
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Solution Overview
Problem
Existing dry molding methods for paper products often result in irregular surface finishes or inadequate strength due to excessive or insufficient wet spreading of starch, leading to the formation of lumps and reduced fiber binding.
Innovation Solution
A method involving the deposition of a fiber-starch mixture in air, followed by controlled moisturizing and heating/pressurizing, where the starch has a setback viscosity of 40 to 200 mPa·s, measured using a rapid visco analyzer, to achieve balanced binding and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wet spreading of starch is increased to improve fiber binding, then the strength of molded body is improved, but irregularities and damas form on the surface reducing smoothness
Solution Approach 1:
The patent applies parameter changes by controlling the setback viscosity of starch within a specific range (40-200 mPa·s) to simultaneously achieve adequate fiber binding and surface smoothness. This quantitative parameter control resolves the contradiction between strength and smoothness by finding the optimal viscosity window where starch provides sufficient binding without excessive wet spreading that causes damas formation.
Solution Approach 2:
The patent introduces dynamics by controlling the gelatinization and retrogradation processes of starch through specific temperature and time conditions during molding. By dynamically managing the starch transformation from raw state through gelatinization to retrogradation, the process achieves balanced fiber binding and surface quality without forming irregularities.
2Manufacturing precision
If the wet spreading of starch is decreased to improve surface smoothness, then surface irregularities are reduced, but fiber binding becomes insufficient reducing molded body strength
Solution Approach 1:
The patent resolves this contradiction by establishing a minimum setback viscosity threshold (40 mPa·s) that ensures adequate fiber binding while preventing excessive wet spreading. This parameter control allows the starch to provide sufficient binding force without creating damas, simultaneously achieving both strength and surface smoothness.
Solution Approach 2:
The patent uses dynamic control of starch gelatinization and retrogradation processes to achieve balanced performance. By managing the temporal evolution of starch properties during molding, the process ensures adequate binding occurs without excessive spreading that would compromise surface quality.
3Strength
If starch is added to bind fibers in dry molding, then fiber binding is achieved, but damas formation occurs causing surface irregularities
Solution Approach 1:
The patent addresses damas formation by controlling the setback viscosity parameter within 40-200 mPa·s, which regulates the wet spreading behavior of starch during dry molding. This parameter optimization prevents the entanglement of fibers into damas while maintaining adequate binding, resolving the contradiction between fiber binding and surface smoothness.
Solution Approach 2:
The patent manages the dynamic process of starch gelatinization and retrogradation under controlled temperature and pressure conditions. By controlling the temporal progression of starch transformation, the process achieves fiber binding without allowing excessive spreading that would cause damas and surface irregularities.
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
This approach enables the production of molded bodies with enhanced surface smoothness and mechanical strength by optimizing starch wet spreading and fiber binding, reducing the formation of lumps and improving tensile strength.
Implementation Method 1
The temperature of the measurement sample is increased from 50° C. to 93° C. over 4 minutes and then maintained at 93° C. for 7 minutes
Implementation Method 2
The temperature of the measurement sample is decreased from 93° C. to 50° C. over 4 minutes and then maintained at 50° C. for 3 minutes
Implementation Method 3
a moisturizing step of applying water to the mixture
Implementation Method 4
a molding step of forming a molded body by heating and pressurizing the mixture to which the water is applied
Implementation Method 5
a molding step of forming a molded body by heating and pressurizing the mixture to which the water is applied
Data Source
AI summary
A method for manufacturing a molded body, includes a deposition step of depositing a mixture containing fibers and a starch in air; a moisturizing step of applying water to the mixture; and a molding step of forming a molded body by heating and pressurizing the mixture to which the water is applied. In the method described above, the starch has a setback viscosity (η50-η93) of 40 to 200 mPa·s, the setback viscosity (η50-η93) being obtained by measurement performed in accordance with the following measurement methods (1) to (4) using a rapid visco analyzer (RVA). The measurement is performed such that (1) after a water suspension containing the starch at 25 percent by mass is charged in the RVA as a measurement sample, the temperature thereof is increased to 50° C. and then maintained for one minute; (2) the temperature of the measurement sample is increased from 50° C. to 93° C. over 4 minutes and then maintained at 93° C. for 7 minutes; (3) the temperature of the measurement sample is decreased from 93° C. to 50° C. over 4 minutes and then maintained at 50° C. for 3 minutes; and (4) in the above (2) and (3), a rotational speed of a measurement paddle of the RVA is set to 960 rpm for 10 seconds after the start of the viscosity measurement and is then set to 160 rpm 10 seconds thereafter.