Tissue Sheet De-bonding via Dissolved Air Expansion
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Solution Overview
Problem
Current methods for producing bulky tissue paper are costly and energy-intensive, often requiring chemical debonders to achieve desired softness and bulk, while also facing challenges with air in wet zones leading to poor formation and drainage issues.
Innovation Solution
A method involving the use of a water-soluble gas under super-atmospheric pressure to form a dissolved gas-impregnated fiber slurry, which is then discharged onto a foraminous support at a lower pressure to create a nascent web that expands and separates, reducing fiber bonding and increasing bulk without chemical debonders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If chemical debonders are added to reduce fiber bonding, then softness and bulk are improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The invention extracts and removes air from the wet end of the papermaking process using a vacuum deaeration system. By removing dissolved air from the fiber slurry before formation, the patent eliminates the need for chemical debonders while achieving the desired fiber separation and bulk properties through physical means alone
Solution Approach 2:
The invention replaces the chemical system (chemical debonders) with a mechanical system (vacuum deaeration apparatus). The vacuum deaeration mechanically removes dissolved air from the fiber slurry, achieving fiber separation without chemical additives, thereby substituting mechanical action for chemical treatment
2Strength
If through air drying is used to increase bulk and reduce strength, then fiber bonding is reduced, but energy consumption increases significantly
Solution Approach 1:
The invention performs preliminary air removal from the fiber slurry before the formation and drying stages. By deaerating the slurry in advance using vacuum, the subsequent drying process requires less energy because there is less dissolved air to evaporate, and the fiber network is already properly formed without excessive bonding
Solution Approach 2:
The invention skips the energy-intensive through air drying step by removing dissolved air beforehand. The vacuum deaeration allows conventional drying to be more efficient, effectively skipping the need for high-energy through air drying while achieving similar bulk and strength properties
3Strength
If air is present in wet zones during papermaking, then fiber separation is improved, but formation quality and drainage deteriorate
Solution Approach 1:
The invention applies local quality control by removing air only from the wet end fiber slurry while maintaining air in the drying sections. The vacuum deaeration is applied specifically to the formation zone to improve drainage and formation quality, while allowing air to remain in the dryer sections to maintain fiber separation and bulk properties
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 results in tissue paper with reduced tensile strength and increased bulk, achieving softness and bulkiness while minimizing energy consumption and chemical debonder usage, with improved air flow and porosity.
Implementation Method 1
exposing an aqueous solution to a water-soluble gas under a super-atmospheric pressure in a contained environment to form a dissolved gas-impregnated solution
Implementation Method 2
discharging the diluted dissolved gas-impregnated fiber slurry from the contained environment directly onto a foraminous support at a lower pressure to form a nascent web
Implementation Method 3
The nascent web is dried to expand, separate, or both expand and separate the dissolved gas-impregnated fibers to form the tissue paper
Data Source
AI summary
Tissue papers and methods of making are disclosed herein. In one aspect, a tissue paper is substantially free of a chemical debonder and has a geometric mean tensile (GMT) in a range between about 500 and about 5,000 g/3 inches (g/3 in.) and a caliper in a range between about 50 and about 350 mils/8 sheets.