Shoe Press Belt Polyurethane Curing
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Solution Overview
Problem
Existing shoe press belts in paper making processes face challenges with cracking resistance, fatigue resistance, and wear resistance, particularly due to the limitations of polyurethane materials used in the outer peripheral layer, which affect the shape retention and mechanical properties under pressure and flexing.
Innovation Solution
A shoe press belt with a reinforcing fiber substrate embedded in polyurethane layers, where the polyurethane is formed by heat-curing a urethane prepolymer with a mixed curing agent comprising 70-99.5 mol% dimethylthiotoluenediamine and 0.5-30 mol% of other curing agents, such as 4,4'-methylenebis(2,6-diethyl-3-chloroaniline) or 1,4-butanediol, enhancing the crack occurrence resistance and low-temperature curability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyurethane materials are used to form the outer peripheral layer of the shoe press belt, then the belt achieves good cracking resistance and wear resistance, but the shape retention properties deteriorate when pressurized by the press roll and shoe
Solution Approach 1:
The patent uses a composite structure consisting of a reinforcing fiber substrate (mesh fabric) embedded in polyurethane layers. The fiber substrate provides tensile strength and shape retention, while the polyurethane layers provide cracking resistance and wear resistance. This composite approach allows both materials to contribute their advantageous properties to the overall belt performance.
2Strength
If polyurethane materials are used to form the outer peripheral layer of the shoe press belt, then the belt achieves good wear resistance, but the mechanical properties deteriorate due to fatigue from flexing
Solution Approach 1:
The fiber substrate embedded in the polyurethane layers acts as a reinforcement that resists fatigue from flexing. The substrate maintains the structural integrity of the belt during repeated flexing cycles, preventing the polyurethane layer from developing fatigue failures while maintaining wear resistance.
3Strength
If conventional curing agents are used to cure the urethane prepolymer, then the polyurethane layer achieves adequate mechanical properties, but the low-temperature curability deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the curing agent from conventional options to cycloaliphatic polyamine curing agents. This parameter change enables the polyurethane system to cure effectively at lower temperatures while maintaining adequate mechanical properties, thus resolving the contradiction between mechanical strength and low-temperature curability.
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 provides shoe press belts with improved crack occurrence resistance and fatigue resistance, maintaining mechanical integrity under flexing and pressure, thus enhancing the belt's performance in paper making processes.
Implementation Method 1
the polyurethane is formed by heat-curing a urethane prepolymer with a mixed curing agent
Implementation Method 2
a urethane prepolymer having a terminal isocyanate group obtained by reacting a diisocyanate compound with a long-chain polyol, and a mixed curing agent
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
A paper making shoe press belt includes a reinforcing fiber substrate (6) and a polyurethane laminate. The reinforcing fiber substrate (6) is embedded in at least one layer (21, 22) of the polyurethane laminate. At least one layer (21, 22)of the polyurethane laminate includes a polyurethane obtained by heat-curing a urethane prepolymer together with a mixed curing agent. The urethane prepolymer includes a terminal isocyanate group and is obtained by reacting a diisocyanate compound and a long-chain polyol. The diisocyanate compound includes at least one of toluene-diisocyanate, diphenylmethane-diisocyanate, and paraphenylene-diisocyanate. The mixed curing agent includes 70-99.5 mol% of dimethylthiotoluenediamine and 0:5-30 mol% of a curing agent. The curing agent includes at least one of 4,4'-methylenebis(2,6-diethyl-3-chloroaniline), 4,4'-methylenedianiline, and 1,4-butanediol. An equivalent ratio of active hydrogen groups of the mixed curing agent to isocyanate groups of the urethane prepolymer is from 1.02 to 1.15.