Papermaking fabrics having machine and cross-machine direction elements and paper products made therewith
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Solution Overview
Problem
Tissue manufacturers face challenges in producing rolled tissue products with high bulk and firmness while maintaining cost-effectiveness, as loosely wound rolls are easily deformed and perceived as soft, making it difficult to balance bulk, firmness, and sheet smoothness, especially in through-air dried tissue products.
Innovation Solution
The use of a papermaking fabric with interwoven shute and warp filaments featuring machine direction (MD) and cross-machine direction (CD) oriented protuberances, where CD protuberances are discrete and cover less than 15% of the surface, enhances tissue web bulk and firmness by structuring the web during manufacturing, allowing for high roll bulk and firmness without compromising operating efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the tissue roll is wound loosely to increase roll bulk, then the roll diameter increases, but the firmness decreases and the roll becomes easily deformed
Solution Approach 1:
The fabric surface is designed with non-uniform local structures including MD-oriented protuberances, CD-oriented protuberances, and valleys with different depths and characteristics. This local variation in fabric topology creates corresponding variations in the tissue web structure, allowing different regions to contribute differently to bulk and firmness properties
Solution Approach 2:
The fabric incorporates three-dimensional surface features (protuberances and valleys) that extend in multiple directions (MD and CD). This multi-dimensional structuring of the fabric surface creates a complex tissue web architecture that simultaneously achieves high bulk through vertical fiber displacement and good firmness through interconnected structural elements
2Strength
If the tissue sheet surface is made smooth to improve perceived softness, then the surface topography is altered, but the ability to wind into firm high bulk finished products becomes difficult
Solution Approach 1:
The fabric creates localized surface features on the tissue web through its MD and CD protuberances and valleys. These local structural variations allow the tissue to maintain surface smoothness in contact regions while preserving bulk through three-dimensional fiber arrangement in non-contact regions
Solution Approach 2:
The fabric surface is segmented into distinct functional zones: MD-oriented protuberances that provide structural support, CD-oriented protuberances that create surface texture, and valleys that accommodate fiber displacement. This segmentation allows independent optimization of smoothness and bulk properties
3Volume of moving object
If through-air dried tissue products are molded into the papermaking fabric to achieve bulk, then the embryonic tissue web is molded, but the molded structure requires calendering to increase sheet smoothness which complicates the process
Solution Approach 1:
The fabric is pre-designed with MD and CD oriented protuberances and valleys that will automatically structure the tissue web during the through-air drying process itself. This preliminary structuring eliminates the need for subsequent calendering operations, as the fabric topology directly imparts the desired bulk and surface properties in one step
Solution Approach 2:
The through-air drying process is enhanced to be self-structuring by incorporating the specialized fabric design. The fabric's three-dimensional topology causes the tissue web to self-organize into bulk-providing structures during drying, and the MD/CD protuberance pattern simultaneously creates acceptable surface smoothness without requiring additional calendering equipment or process steps
Data Source
AI summary
The present invention discloses a papermaking fabric having a both machine direction (MD) and cross-machine direction (CD) oriented protuberances for molding and structuring a nascent paper web, particularly tissue paper webs. The MD orientated protuberances are spaced apart from one another in the fabric cross-machine direction and may be continuous and parallel to one another. The CD orientated protuberances are preferably discrete and comprise less than about 15 percent of the web contacting surface of the fabric. In certain instances the MD orientated protuberances are formed from interwoven filaments and the CD orientated protuberances are nonwoven and may be applied to the woven fabric substrate by printing.