Polyisocyanate Composition for Coating Adhesiveness and Low-Temperature Curability
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Solution Overview
Problem
Current polyisocyanate compositions used in urethane coating materials face challenges with adhesiveness and low-temperature curability when forming a coating film, necessitating improvements in these properties.
Innovation Solution
A polyisocyanate composition is developed using a combination of aliphatic and alicyclic diisocyanates with a polyol, optimizing the content of structural units, isocyanate functional groups, and molecular weights to enhance adhesiveness and low-temperature curability, incorporating specific functional groups like allophanate, uretdione, and isocyanurate for improved weather resistance and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyisocyanate derived from an aliphatic diisocyanate, a monoalcohol, and a polyol is used, then compatibility with main agent and curability are improved, but adhesiveness and low-temperature curability are insufficient
Solution Approach 1:
The patent changes the molecular weight parameter of the polyol from conventional values to specifically 400-2000, and adjusts the structural unit content parameters (aliphatic diisocyanate 10-80 mass%, alicyclic diisocyanate 10-80 mass%, polyol 10-80 mass%) to achieve optimal balance between curability and adhesiveness
Solution Approach 2:
The patent creates a composite polyisocyanate composition by combining multiple diisocyanate types (aliphatic and alicyclic) with polyol in specific ratios, achieving synergistic effects that improve both adhesiveness and low-temperature curability beyond what single-component systems can provide
2Reliability
If the polyisocyanate composition is optimized for curability, then durability is improved, but low-temperature curability remains insufficient
Solution Approach 1:
The patent optimizes the molecular weight parameter of polyol to 400-2000 (specifically 600-1500 in preferred embodiments) and controls the NCO functional group content at 3-15 mass%, enabling the coating to cure effectively at low temperatures while maintaining durability through controlled crosslinking density
3Strength
If the polyisocyanate composition is optimized for adhesiveness, then coating strength is improved, but flexibility and hardness balance is compromised
Solution Approach 1:
The patent carefully controls the molecular weight of polyol within 400-2000 and the ratio of aliphatic to alicyclic diisocyanate structural units to achieve optimal crosslinking density, which simultaneously provides strong adhesiveness while maintaining the flexibility-hardness balance required for coating performance
Solution Approach 2:
The patent introduces different diisocyanate structural units (aliphatic and alicyclic) with distinct properties into the same polymer chain structure, creating local variations in crosslinking characteristics that collectively provide both strong adhesion and appropriate mechanical flexibility
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 optimized polyisocyanate composition exhibits enhanced adhesiveness, low-temperature curability, and pressure-sensitive adhesiveness, leading to improved durability and water-resistance of the coating film, while maintaining flexibility and hardness.
Implementation Method 1
An isocyanate group contained in the polyisocyanate as a curing agent reacts with a hydroxy group of a polyol frequently used as a main agent
Implementation Method 2
incorporating specific functional groups like allophanate, uretdione, and isocyanurate for improved weather resistance and flexibility
Data Source
AI summary
A polyisocyanate composition is provided having excellent adhesiveness and low-temperature curability when formed into a coating film. The polyisocyanate composition is a polyisocyanate composition including a polyisocyanate obtained from at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate, and a polyol having a number-average molecular weight from 400 to 5,000 and an average number of hydroxy groups from 3 to 8, in which a content of a structural unit derived from the polyol is from 22% by mass to 80% by mass with respect to a total mass of the polyisocyanate composition, an average number of isocyanate functional groups is from 3.5 to 20, and a weight-average molecular weight/a number-average molecular weight is from 3.5 to 15.