Polyurethane Press Cover Hydrophobicity via Carbonate Polyol Structure
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Solution Overview
Problem
Press covers and transport belts for shoe presses and paper machines require improved hydrophobicity while maintaining wear resistance, abrasion resistance, cracking resistance, chemical resistance, flexibility, and stiffness, as existing polyurethane-based solutions do not adequately address hydrophobicity on the paper side.
Innovation Solution
A polyurethane layer is developed with a polyol component composed of structural units following the formula —O—R1—X—R2—O—, where R1 and R2 are C1-C20 alkylene groups and X includes bond, O, C(O)—O, and O—C(O)—O, with at least 70% of units meeting criteria of high O—C(O)—O content, long chain length, and C8-C12 alkylene groups, enhancing hydrophobicity and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional polyurethane-based press covers are used, then mechanical properties such as wear resistance and flexibility are maintained, but hydrophobicity on the paper side is insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyol component, specifically incorporating polyols with carbonate groups (—O—C(O)—O—) and adjusting the molecular weight distribution (500-10000 g/mol). This chemical parameter change transforms the surface properties of the polyurethane layer, enhancing hydrophobicity while preserving mechanical integrity through controlled polymer chain structure.
Solution Approach 2:
The invention creates a composite polyurethane system by combining multiple polyol components (carbonate-containing polyols, polyester polyols, polyether polyols) with diisocyanates and crosslinking agents. This multi-component composite approach allows simultaneous optimization of hydrophobicity (through carbonate groups) and mechanical properties (through crosslinked network structure).
2Ease of operation
If the press cover is made more flexible to wrap around the shoe, then it can be passed around the shoe, but stiffness under pressing load may be compromised
Solution Approach 1:
The patent implements local quality differentiation through a multi-layer construction where the polyurethane coating (0.5-5 mm thick) provides localized flexibility and hydrophobicity on the paper-contact surface, while the underlying fiber-reinforced structure (glass fiber, basalt fiber, or aramid fiber) provides localized stiffness and load-bearing capacity. This spatial differentiation of material properties resolves the flexibility-stiffness contradiction.
Solution Approach 2:
The press cover employs a composite structure combining polyurethane polymer matrix with embedded textile reinforcement (woven or non-woven fiber fabrics). The polyurethane component provides flexibility and hydrophobicity, while the fiber reinforcement network provides stiffness and tensile strength under pressing loads, achieving both requirements simultaneously.
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 polyurethane layer exhibits improved hydrophobicity, wear resistance, abrasion resistance, and chemical resistance, maintaining flexibility and stiffness, thereby optimizing performance in dewatering fibrous webs and paper machines.
Implementation Method 1
the polyol component of the polyurethane is composed to an extent of at least 90 wt % of one or more mutually different structural units according to the following general formula (I), in which all of R1 and R2 in the one or more different structural units according to the general formula (I) independently of one another are identical or different and are selected from linear C1-C20 alkylene groups and branched C1-C20 alkylene groups, and all of groups X in the one or more different structural units independently of one another are identical or different and are selected from bond, O, C(O)—O and O—C(O)—O, where at least 70 wt % of the structural units according to the general formula (I) meet the following criteria: a) at least 80% of the groups X are O—C(O)—O and the remainder of the groups X are selected from O and C(O)—O, and b) the average chain length of all the groups R1 and R2 is 8 or more than 8 carbon atoms, and c) at least 50% of the groups R1 and R2 are independently of one another each a linear or branched C8-C12 alkylene group
Data Source
AI summary
A press cover for a press roll or a transport belt has at least one polyurethane-containing layer. The polyurethane is obtainable by reaction of i) a polyol component, ii) an isocyanate component, and iii) a component containing at least one crosslinker. The polyol component is composed of mutually different structural units having the general formula —O—R1—X—R2—O— in which all of R1 and R2 independently of one another are identical or different and are linear or branched C1-C20 alkylene groups. Groups X are identical or different and are selected from bond, O, C(O)—O, and O—C(O)—O. At least 70 wt % of the structural units meet the following criteria: a) at least 80% of X are O—C(O)—O and the remainder are O or C(O)—O, and b) the average chain length of R1 and R2 is 8 or more carbon atoms, and c) at least 50% of R1 and R2 are independently of one another a linear or branched C8-C12 alkylene group.