Indirect Curtain Sizing of Fiber Webs with Hard Rolls
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Solution Overview
Problem
Current methods for treating fiber webs with high solids sizing agents face challenges in achieving a non-porous, strong, and evenly coated surface, which affects the fiber web's strength, stiffness, and printing properties, while also leading to dusting issues.
Innovation Solution
The method involves indirect curtain sizing using metallic or ceramic rolls with a hard sizing nip, followed by immediate contactless drying in an air-borne system, ensuring the sizing agent remains on the surface and enhancing the fiber web's strength and stiffness, with adjustable air compartments for optimal drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional sizing methods are used to apply sizing agents onto fiber web surfaces, then coating coverage can be achieved, but the sizing agent penetrates into the fiber web causing dusting and reducing surface strength
Solution Approach 1:
The patent applies preliminary action by using a sizing press with heated rolls to pre-size the fiber web before it reaches the drying section. The sizing agent is applied under pressure and heat in advance, creating a preliminary bond that prevents subsequent dusting issues during drying and handling.
Solution Approach 2:
The patent changes parameters by controlling the temperature and pressure conditions in the sizing press. The heated rolls (typically 60-100°C) and applied pressure modify the physical state of the sizing agent to enhance surface bonding while minimizing penetration, thereby improving surface strength and reducing dusting.
2Reliability
If high solids content sizing agents are used to improve surface properties, then coating adherence improves, but the fiber web becomes more porous and less uniform
Solution Approach 1:
The patent changes the concentration parameter of the sizing agent to use high solids content formulations (typically 40-60% solids). This high concentration provides better coating adherence and surface properties while the controlled application method maintains surface uniformity.
Solution Approach 2:
The patent uses a smooth, polished roll surface in the sizing press that acts as a template or copy for the fiber web surface. This smooth contact surface ensures uniform distribution of the high solids content sizing agent, creating a consistent coated surface that maintains both adherence and uniformity.
3Quantity of substance
If the fiber web is dried using conventional contact drying methods, then moisture removal is achieved, but the fiber web surface becomes rough and porous
Solution Approach 1:
The patent replaces conventional mechanical contact drying methods with a non-contact infrared heating system. The infrared radiation directly heats the fiber web surface to evaporate moisture without mechanical contact, thereby removing moisture while maintaining surface smoothness and preventing porosity formation.
Solution Approach 2:
The patent utilizes phase transition by using infrared radiation to directly heat the moisture in the fiber web, causing rapid evaporation (liquid to gas phase change). This non-contact thermal energy transfer removes moisture efficiently while preserving the surface integrity and smoothness of the fiber web.
4Quantity of substance
If the fiber web is sized and then dried with a long run between processes, then drying can be more thorough, but the sizing agent redistributes and surface strength decreases
Solution Approach 1:
The patent merges the sizing and drying processes into a closely integrated sequence where the sizing press is immediately followed by the infrared drying section. This merging eliminates long runs between processes, preventing sizing agent redistribution while achieving thorough drying through the powerful infrared heating system.
Solution Approach 2:
The patent applies preliminary sizing action right before drying in a tightly coupled process sequence. The sizing agent is applied under pressure and heat immediately prior to infrared drying, ensuring proper placement and activation before moisture removal, thereby maintaining surface strength throughout the drying process.
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 significantly improves the surface strength and stiffness of the fiber web, reduces dusting, and enhances coating adherence, while maintaining a smooth surface and minimizing porosity, thus improving the overall quality of the fiber web.
Implementation Method 1
drying by an air-borne drying system, in which the fiber web is dried in a contactless manner by heated air blows
Implementation Method 2
drying by an air-borne drying system, in which the fiber web is dried in a contactless manner by heated air blows
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method of treating a fiber web, in which method the fiber web is sized in a sizer (10) by indirect curtain sizing in a curtain sizer (10), in which the sizing agent (TA, TB) is applied onto at least one side of the fiber web by two sizing rolls (11A,11B) with metallic or ceramic surface or with polymeric surface, which polymeric surface has surface hardness 60 ― 100 shoreD, advantageously 80 - 95 shoreD, in a sizing nip (N), in which the fiber web (W) is sized with high solids content sizing agent (TA, TB) having solids content of 10 ― 60 %, preferably 20 ― 40 %, and viscosity of 50 cP- 2000 cP, preferably 100 cP ― 1500 cP, and the sizing agent (TA; TB) is applied onto the at least one side of the fiber web (W) by the two sizing rolls (11A,11N), in the sizing nip (N). After the sizing the fiber web (W) is directly guided to contactless and supported drying in an air-borne drying system (20) and the run of the fiber web (W) from the sizing nip (N) to beginning of the drying in the air-borne drying system (20) is not more than 2 m, advantageously not more than 0,5 m, and / or takes not more time than 0,5 s. The invention also relates to a treatment system for treatment of a fiber web, which treatment system comprises a sizer (10), which is a curtain sizer (10) with at least one curtain application device (12A; 12B) for indirect application of sizing agent (TA; TB) and comprises two hard sizing rolls (11A, 11B) with metallic or ceramic surface or with polymeric surface, which polymeric surface has surface hardness 60 ― 100 shoreD, advantageously 80 ― 95 shoreD, and forming a sizing nip (N), which curtain sizer (10) with the indirect application of sizing agent (TA, TB) is configured to apply the sizing agent (TA, TB) in high solids content of 10 ― 60 %, preferably 20 ― 40 % and in viscosity of 100 cP or over, preferably 1050 cP― 2000 cP, more preferably 100 cP ― 1500 cP. The treatment system further comprises an immediately after the sizer (10) located air-borne drying system (20) such, that the run of the fiber web (W) from the sizing nip (N) to beginning of the drying in the air-borne drying system (20) is not more than 2 m, advantageously not more than 0,5 m, and / or takes not more time than 0,5 s.