Tissue Press Felt Structure for Higher Dewatering in Long Nips
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Solution Overview
Problem
Modern tissue machines face limitations in production speed due to insufficient dewatering of the tissue web in the press nip, necessitating improved drainage solutions.
Innovation Solution
A covering for tissue machines comprising a woven textile structure with medium-density threads and a reduced nonwoven layer, optimized for uniform pressure distribution and enhanced dewatering capabilities, combined with a press device featuring a long nip and wastewater traps to enhance dewatering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional fabrics are used in tissue machine drying sections, then the fabric can be easily manufactured, but the fabric lacks sufficient strength to resist high mechanical loads and causes frequent breaks requiring stops for replacement
Solution Approach 1:
The fabric is constructed as a composite material combining natural fibers (cellulose, wood pulp, bamboo, or cotton linters) with synthetic polymer fibers (polyester, polyamide, acrylic, or polypropylene). This composite structure provides both the strength needed to resist high mechanical loads in the drying section and the porosity required for tissue production, resolving the contradiction between strength and manufacturability.
Solution Approach 2:
The fabric employs different fiber types in different regions or layers to optimize local properties. The composite construction allows certain areas to provide structural strength while other areas maintain porosity and flexibility, enabling the fabric to withstand mechanical loads without requiring uniform complexity throughout the entire structure.
2Strength
If the fabric structure is made more complex to improve strength, then the fabric can resist higher mechanical loads, but the manufacturing process becomes more difficult and costly
Solution Approach 1:
By using composite materials with natural and synthetic fibers, the fabric achieves high strength through the inherent properties of the fiber combination rather than through complex structural designs. This allows standard manufacturing processes to produce a fabric that meets the high strength requirements, maintaining ease of manufacture while improving strength.
Solution Approach 2:
The invention changes the material parameters by selecting specific natural fibers (cellulose, wood pulp, bamboo, or cotton linters) combined with specific synthetic polymers (polyester, polyamide, acrylic, or polypropylene). These parameter selections optimize the balance between strength and manufacturability, allowing the fabric to be produced using conventional processes while achieving the required mechanical properties.
3Strength
If a new high-strength fabric is developed, then the fabric can withstand high mechanical loads, but the cost of raw materials and production increases
Solution Approach 1:
The composite structure allows the use of cost-effective natural fibers (which are abundant and inexpensive) combined with smaller amounts of synthetic fibers that provide the necessary strength enhancement. This combination achieves high strength requirements while controlling raw material costs, as the natural fibers provide bulk and the synthetic fibers provide strength reinforcement.
Solution Approach 2:
By selecting from specific groups of natural fibers (cellulose, wood pulp, bamboo, or cotton linters) and synthetic polymers (polyester, polyamide, acrylic, or polypropylene), the invention optimizes the cost-strength relationship. These material selections represent a balance between availability, cost, and performance, allowing the fabric to meet high strength requirements without excessive material costs.
4Strength
If the fabric is designed for high strength in the drying section, then the fabric can resist mechanical loads, but the fabric loses flexibility and adaptability for different tissue production requirements
Solution Approach 1:
The composite construction with natural and synthetic fibers creates a fabric that inherently combines strength with flexibility. The natural fiber components provide flexibility and adaptability, while the synthetic fiber components provide strength, allowing the same fabric structure to serve multiple functions across different sections of the tissue machine and adapt to various tissue production requirements.
Solution Approach 2:
The fabric's composite structure allows different regions or layers to have optimized properties for different functions. This local quality differentiation enables the fabric to maintain high strength where needed while preserving flexibility and adaptability in other areas, allowing a single fabric design to serve multiple purposes in tissue production.
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 enables improved dewatering performance, allowing high-speed production by increasing the dry content of the tissue web, reducing nonwoven material usage, and minimizing fiber compression losses, thus enhancing machine productivity.
Implementation Method 1
the blend fabric can be used to control humidity in the drying section of a tissue machine
Data Source
Figure 1
AI summary
The invention relates to a fabric, in particular felt, for use in a machine for producing a tissue web, comprising a base structure, which has a textile structure with MD threads, and at least one layer of nonwoven fibers. The invention is characterized in that the MD threads predominantly or as a whole have a diameter ranging between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the thread density of the MD threads is more than 37%, in particular between 37% and 45%. The invention additionally relates to a machine and a method for producing a tissue web using such a fabric.