Two-Pack Urethane Adhesive With Low-Solvent Handling and Strong Cure
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Solution Overview
Problem
Existing urethane adhesives have low tack and poor adhesive properties, are brittle, and require solvents for handling, which is undesirable for environmental and medical applications.
Innovation Solution
A two-component curable urethane adhesive system comprising a hydroxy group-containing urethane prepolymer and an isocyanate group-containing urethane prepolymer, with specific molecular weight ranges and low solvent content, allowing for easy handling and strong adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the molecular weight of prepolymer is increased to improve physical properties of cured film, then the adhesive strength and film properties are improved, but the viscosity becomes high resulting in poor handling properties
Solution Approach 1:
The invention divides the single-component system into two separate components: a hydroxy group-containing urethane prepolymer and a curing agent. This segmentation allows each component to have optimized molecular weight and viscosity for easy handling, while their combination provides the high molecular weight and crosslinking density needed for strong adhesive properties and excellent cured film characteristics.
Solution Approach 2:
The invention changes the molecular weight parameters of the prepolymer components to specific ranges (weight average molecular weight 1,000-100,000) to balance handling viscosity with adhesive strength. Additionally, the polyol component is designed with specific molecular weight (200-12,000) and functional group ratios to achieve optimal performance without excessive viscosity.
2Ease of operation
If organic solvents are used to reduce viscosity and improve handling properties, then the handling properties are improved, but environmental pollution increases and medical applications are restricted
Solution Approach 1:
The invention extracts and eliminates organic solvents from the adhesive formulation. By using a two-component system with low molecular weight prepolymers and controlling the polyol molecular weight and structure, the invention achieves adequate handling viscosity without requiring solvent dilution, thereby eliminating VOC emissions and enabling safe medical applications.
3Strength
If a large amount of curing agent or increased crosslinking points are used to impart strength to adhesive sheet, then the adhesive strength is improved, but the cured film becomes brittle with poor flexibility
Solution Approach 1:
The invention optimizes the molecular weight of the polyol component to 200-12,000 and controls the functional group ratios (with at least 40% of terminal groups being hydroxyl groups) to achieve balanced crosslinking density. This parameter optimization provides sufficient adhesive strength while maintaining flexibility and preventing brittleness in the cured film.
Solution Approach 2:
The invention creates a composite adhesive system combining hydroxy group-containing urethane prepolymer with specific polyol structures and a curing agent. This composite formulation achieves balanced crosslinking that provides both strength and flexibility, avoiding the brittleness associated with excessive crosslinking.
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 adhesive achieves easy-to-handle viscosity, weak to strong adhesive capabilities, and forms a cured film with excellent properties, addressing environmental and medical application needs.
Implementation Method 1
the hydroxy group-containing urethane prepolymer (P1) being a reaction product between the polyol component (A) and an organic polyisocyanate component (B)
Implementation Method 2
a two-component curable urethane adhesive containing: a main agent; and a curing agent
Data Source
AI summary
The present invention aims to provide a two-component curable urethane adhesive that is easy to handle while it is substantially solvent-free, having weak to strong adhesive properties, and being capable of forming a cured film having excellent physical properties. The present invention provides a two-component curable urethane adhesive containing: a main agent; and a curing agent, the main agent containing at least one of a hydroxy group-containing urethane prepolymer (P1) or a polyol component (A), the hydroxy group-containing urethane prepolymer (P1) being a reaction product between the polyol component (A) and an organic polyisocyanate component (B), the curing agent containing at least one of an isocyanate group-containing urethane prepolymer (P2) or an organic polyisocyanate component (B), the isocyanate group-containing urethane prepolymer (P2) being a reaction product between the polyol component (A) and the organic polyisocyanate component (B), wherein the two-component curable urethane adhesive satisfies the following properties (1) to (5): (1) at least one of the polyol component (A) used in the hydroxy group-containing urethane prepolymer (P1) or the polyol component (A) used as the main agent contains a polyol (A1) having at least one of a group represented by a formula (1) or a group represented by a formula (2) at a molecular end thereof, and a total number of groups represented by the formula (1) in the polyol (A1) accounts for 40% or more based on a total number of groups represented by the formulas (1) and (2) in the polyol (A1) ; (2) an average total unsaturation degree of all the polyol components (A) used in the two-component curable urethane adhesive is 0.010 meq/g or less; (3) a weight average molecular weight of each of the urethane prepolymer (P1) and the urethane prepolymer (P2) is 1,000 to 100,000; (4) a chemical formula weight or number average molecular weight of each of the polyol component (A) and the organic polyisocyanate component (B) is 20,000 or less; and (5) a total weight of solvents in the main agent (excluding the polyol component (A)) and solvents in the curing agent (excluding the organic polyisocyanate component (B)) accounts for 5 wt% or less based on a total weight of the main agent and the curing agent, wherein in the formulas (1) and (2), each a is independently an integer of 0 or greater.