Water-disintegrable sheet and method for manufacturing water-disintegrable sheet
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Solution Overview
Problem
Conventional water-disintegrable sheets often tear during strong rubbing in toilet cleaning due to insufficient tear resistance, while increasing the concentration of CMC to enhance surface strength compromises water-disintegrability.
Innovation Solution
A water-disintegrable sheet with a base paper sheet impregnated using a water-soluble binder and cellulose nanofibers, where the binder and nanofiber content gradually increase from the inside to the outside, and a cross-linking agent is applied to enhance tear resistance without compromising water-disintegrability, using a Gakushin type fastness rubbing tester to achieve a minimum average value of 40 in wear resistance tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the concentration of CMC solution is increased to improve surface strength, then tear resistance is improved, but water-disintegrability decreases
Solution Approach 1:
The patent applies different concentrations of CMC solution to different regions of the base paper sheet. The outer surface receives a higher concentration (at least 3.3%) to achieve tear resistance, while the inner region maintains lower concentration to preserve water-disintegrability. This spatial differentiation of material properties resolves the contradiction between strength and disintegrability.
Solution Approach 2:
The patent transitions from uniform impregnation to gradient impregnation through the thickness dimension of the paper sheet. By controlling the concentration distribution from outer surface to inner core, the invention achieves both high surface strength and good water-disintegrability by utilizing the thickness dimension for functional differentiation.
2Strength
If a water-soluble binder is added to improve paper strength in wet state, then tear resistance is improved, but water-disintegrability decreases
Solution Approach 1:
The water-soluble binder (CMC) is selectively concentrated at the outer surface of the base paper sheet through controlled impregnation. This localized application provides the necessary wet strength for tear resistance during wiping operations while keeping the inner regions binder-free to ensure rapid water-disintegrability in the toilet tank.
3Ease of operation
If strong rubbing is applied during toilet cleaning, then cleaning effectiveness is improved, but the sheet tears due to insufficient tear resistance
Solution Approach 1:
The patent reinforces the outer surface where the user contacts the sheet during rubbing operations. By concentrating the water-soluble binder and cellulose nanofibers at the surface, the sheet can withstand strong rubbing forces during cleaning while maintaining the ability to disintegrate after use.
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 solution improves tear resistance against strong rubbing while maintaining water-disintegrability, enhancing the wiping property of the sheet.
Implementation Method 1
the aqueous agent includes a cross-linking agent which cross-links with a water-soluble binder
Data Source
AI summary
A water-disintegrable sheet in which a base paper sheet is impregnated with an aqueous agent is provided. The base paper sheet has a weight per unit area of 30 to 150 gsm and includes a water-soluble binder and cellulose nanofibers. The aqueous agent includes a cross-linking agent which cross-links with a water-soluble binder. In the base paper sheet, content of the water-soluble binder and content of the cellulose nanofibers gradually increase from inside toward outside of the base paper sheet in a thickness direction. When a wear resistance test is performed three times using a Gakushin type fastness rubbing tester with a PP band as a rubbing finger and an average of measured values for the three times is calculated for each of a MD direction and a CD direction, each average value is at least 40.