Two-Component Polyurethane Adhesive Temperature Stability

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Solution Overview

Problem

Two-component polyurethane compositions used as adhesives, sealing compounds, or infusion resins face challenges in maintaining high strength over a broad temperature range (−40° C. to +100° C) with minimal temperature dependence, while also avoiding foaming reactions and ensuring good adhesion to fiber-reinforced plastics.

Innovation Solution

A two-component polyurethane composition comprising a polyol component with a polyester polyol based on dimer fatty acids, a polybutadiene polyol, and an alkoxylated alkylenediamine, combined with an aromatic polyisocyanate, which cures without foaming and maintains high tensile strength and adhesion across a wide temperature range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional polyurethane compositions are used to achieve high strength, then tensile strength is improved, but temperature dependence of mechanical properties increases

Engineering Contradiction:

Improvetensile strengthVSAvoidtemperature dependence of mechanical properties

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent uses a composite polyol system combining polyester polyol (providing strength and rigidity) with polyether polyol (providing flexibility and temperature stability). This composite material approach allows the adhesive to maintain high tensile strength while reducing temperature dependence of mechanical properties across the range from -40°C to +100°C.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including OH number (65-350 mg KOH/g), molecular weight (500-2000 g/mol), and glass transition temperature (-80°C to -20°C) of the polyester polyol, along with polyether polyol ratios, to achieve the desired balance between strength and temperature stability.

Inventive Principle:

Principle #35Parameter changes

2Speed

If polyol compositions are used that cure rapidly, then curing speed is improved, but foaming reaction increases

Engineering Contradiction:

Improvecuring speedVSAvoidfoaming reaction

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent carefully controls the OH number (65-350 mg KOH/g) and water content (<0.05% by weight) of the polyester polyol, along with the NCO:OH ratio (0.9:1 to 1.1:1), to achieve rapid curing through isocyanate-hydroxyl reaction while minimizing foaming reactions that would occur with excessive moisture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a specific polyester polyol based on dimer fatty acids with controlled molecular structure and properties, creating a localized chemical environment that favors the desired polyurethane formation reaction over competing foaming reactions with moisture.

Inventive Principle:

Principle #3Local quality

3Strength

If conventional adhesives are used to achieve good adhesion, then adhesion is improved, but adhesion performance over broad temperature range deteriorates

Engineering Contradiction:

ImproveadhesionVSAvoidadhesion over broad temperature range

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The composite polyol system with polyester polyol (OH number 65-350 mg KOH/g, molecular weight 500-2000 g/mol, glass transition temperature -80°C to -20°C) combined with polyether polyol provides both strong adhesion to substrates including fiber-reinforced plastics and maintained adhesion performance across the broad temperature range from -40°C to +100°C.

Inventive Principle:

Principle #40Composite materials

4Strength

If high molecular weight polyols are used to increase strength, then tensile strength is improved, but processability deteriorates

Engineering Contradiction:

Improvetensile strengthVSAvoidprocessability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent optimizes the molecular weight of polyester polyol to 500-2000 g/mol and controls OH number (65-350 mg KOH/g) to achieve the optimal balance between tensile strength and processability, allowing the adhesive to be easily applied and processed while maintaining high strength after curing.

Inventive Principle:

Principle #35Parameter changes

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 composition exhibits high tensile strength and moduli of elasticity with minimal temperature dependence, excellent adhesion to carbon fiber-reinforced plastics, and resistance to foaming reactions, making it suitable for structural adhesives and infusion resins.

Implementation Method 1

Two-component polyurethane adhesives based on polyols and polyisocyanates have already been used for some time

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Implementation Method 2

cure without formation of foam on the basis of a reaction of isocyanate groups with moisture

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS11680131B2Two-component polyurethane composition

Publication Date: 2023.06.20 SIKA TECH AG

AI summary

A two-component polyurethane composition including a polyol component and a polyisocyanate component, wherein the polyol component comprises at least one polyester polyol A1 based on dimer fatty acids and/or dimer fatty alcohols having an OH number of 65-350 mg KOH/g, at least one polybutadiene polyol A2 and at least one alkoxylated alkylenediamine A3. The polyurethane composition has high strength and only a minor dependence of the mechanical properties, especially strength, on temperature, especially in the range from −40° C. to +100° C.