Rigid Polyurethane Foam Isocyanate Composition

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Solution Overview

Problem

Rigid polyurethane foams face challenges with dimensional stability and long demolding times, particularly in large moldings, leading to shrinkage and detachment issues, and there is a need for foams with low density and quick demolding capabilities.

Innovation Solution

A specific composition of diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates, with a mixture of 30-35% diphenylmethane diisocyanate, 21-28% polyphenylenepolymethylene polyisocyanate with three aromatic rings, 8-13% with four aromatic rings, and 24-41% with five or more aromatic rings, is used as the isocyanate component, along with polyether alcohols and blowing agents, to produce foams with improved processing and use properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polyisocyanate mixtures are used, then production cost is reduced, but dimensional stability deteriorates causing shrinkage and voids

Engineering Contradiction:
Improvedimensional stabilityVSAvoidproduction complexity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by precisely controlling the composition ratios of different polyisocyanate components (MDI content between 30-35%, specific distribution of polymeric MDI with 3-5 aromatic rings) to achieve optimal dimensional stability. This quantitative parameter optimization resolves the contradiction by finding the precise compositional window that delivers both reliability and manufacturability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention uses composite materials by combining multiple polyisocyanate types (monomeric MDI and polymeric MDI with specific aromatic ring counts) in defined proportions. This composite approach allows the formulation to balance reactivity, foam structure formation, and dimensional stability, overcoming the limitations of single-component systems while maintaining production feasibility.

Inventive Principle:
Principle #40Composite materials

2Use of energy by moving object

If foam density is reduced, then thermal insulation performance is improved, but mechanical strength deteriorates

Engineering Contradiction:
Improvethermal insulation performanceVSAvoidmechanical strength
Core Design Contradiction:
Use of energy by moving objectVSStrength

Solution Approach 1:

The patent employs parameter changes by optimizing the polyisocyanate composition to achieve low foam density (below 30 g/l) while maintaining mechanical strength. The specific ratio of monomeric to polymeric MDI, along with control over aromatic ring content, modifies the foam cell structure and wall strength, enabling lightweight foams that retain adequate mechanical properties for structural applications.

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 solution results in rigid polyurethane foams with low shrinkage, excellent dimensional stability, and quick demolding, achieving densities below 30 g/l while maintaining good thermal insulation properties.

Implementation Method 1

reacting polyisocyanates, usually diphenylmethane diisocyanate (MDI) and in particular mixtures of diphenylmethane diisocyanate and its higher homologues polyphenylenepolymethylene polyisocyanates (crude MDI), with compounds having at least two hydrogen atoms which are reactive toward isocyanate groups

Methodology Applied
Scientific EffectChemical reaction between isocyanate groups and reactive hydrogen compounds: Chemical Bonding

Implementation Method 2

reacting with compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence of blowing agents

Methodology Applied
Scientific EffectGas generation from blowing agents:

Data Source

PatentUS9657133B2Rigid polyurethane foams
Publication Date: 2017.05.23 BASF SE

AI summary

The invention relates to rigid polyurethane foams which can be produced by reactinga) polyisocyanates withb) compounds having at least two hydrogen atoms which are reacted toward isocyanate groups in the presence ofc) blowing agents,wherein the polyisocyanate a) used is a mixture of diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates comprisinga1) 30-35% by weight of diphenylmethane diisocyanate,a2) 21-28% by weight of polyphenylenepolymethylene polyisocyanate having three aromatic rings,a3) 8-13% by weight of polyphenylenepolymethylene polyisocyanate having four aromatic rings,a4) 24-41% by weight of polyphenylenepolymethylene polyisocyanate having five or more aromatic rings,where the percentages by weight of the components a1) to a4) are based on the total weight of the components a1) to a4) and add up to 100% by weight.