Polyester Polyols Secondary Hydroxyl End Groups Catalyst
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Solution Overview
Problem
Conventional polyester polyols with secondary hydroxyl end groups are more expensive and less suitable for producing high-quality polyurethane foams due to their lower reactivity and poorer properties compared to those with primary hydroxyl end groups, limiting their technical significance.
Innovation Solution
A process involving the reaction of polyesters with carboxyl end groups and an epoxide in the presence of a nitrogen-containing catalyst, adjusting acid and hydroxyl values to produce polyester polyols with a higher proportion of secondary hydroxyl end groups, allowing for a broader range of catalyst systems and improved properties in polyurethane polymers and foams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyester polyols with secondary hydroxyl end groups are produced using diols with secondary hydroxyl groups (e.g., 1,2-propylene glycol, 2,3-butanediol), then the polyester polyols exhibit secondary hydroxyl end groups, but the manufacturing cost increases and the properties of the resulting polyurethanes deteriorate
Solution Approach 1:
The invention changes the chemical parameter of the end groups from primary hydroxyl to secondary hydroxyl groups by using a two-stage process: first producing polyesters with carboxyl end groups, then reacting them with epoxides. This parameter change enables the use of tin catalysts instead of amine catalysts, improving polyurethane quality while controlling costs through process optimization
Solution Approach 2:
The invention segments the polyester polyol structure into two distinct parts: α,ω-diol units in the interior (maintaining good properties) and chain-end units with secondary hydroxyl groups (enabling catalyst versatility). This segmentation allows the molecule to exhibit both desirable reactivity and catalytic flexibility
2Adaptability or versatility
If diols with secondary hydroxyl end groups are used in polyester synthesis, then polyester polyols with secondary hydroxyl end groups are obtained, but the reactivity towards polyisocyanates decreases
Solution Approach 1:
The invention changes the hydroxyl group type at chain ends to secondary hydroxyl groups, which inherently reduces reactivity towards polyisocyanates. This parameter change is deliberately made to enable the use of tin catalysts, trading some reaction speed for catalyst versatility and improved polyurethane properties
Solution Approach 2:
The invention introduces tin salts as intermediary catalysts that can effectively catalyze the reaction between polyester polyols with secondary hydroxyl end groups and polyisocyanates. These tin catalysts compensate for the reduced inherent reactivity, enabling the process to proceed at practical rates while maintaining catalyst versatility
3Reliability
If polyester polyols with secondary hydroxyl end groups are produced using conventional methods, then the polyols are obtained, but the production cost increases due to expensive diol materials
Solution Approach 1:
The invention segments the molecular structure to place secondary hydroxyl groups only at chain ends rather than throughout the entire molecule. This is achieved by reacting polyesters with carboxyl end groups with epoxides, concentrating the expensive secondary hydroxyl functionality at the terminals while keeping the bulk material cost-effective
Solution Approach 2:
The invention changes the production methodology from direct polyesterification with secondary diols to a two-stage process involving epoxide reaction with carboxyl-terminated polyesters. This parameter change in the synthesis route reduces material costs while maintaining the desired secondary hydroxyl end group structure
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
This process enables the production of polyester polyols with improved reactivity and properties, enabling the use of tin catalysts instead of amine catalysts, reducing odour and enhancing the ageing resistance of polyurethanes, and offering processing advantages in polyurethane flexible foams.
Implementation Method 1
the reaction of a polyester including carboxyl end groups with an epoxide
Implementation Method 2
in the presence of a catalyst that includes at least one nitrogen atom per molecule
Data Source
AI summary
The invention relates to a process for producing polyester polyols with secondary hydroxyl end groups, including the step of the reaction of a polyester including carboxyl end groups with an epoxide of the general formula (1):wherein R1 stands for an alkyl residue or an aryl residue and the reaction is carried out in the presence of a catalyst that includes at least one nitrogen atom per molecule. The process is distinguished in that the polyester including carboxyl end groups exhibits an acid value from ≧25 mg KOH/g to ≦400 mg KOH/g and a hydroxyl value from ≦5 mg KOH/g and in that the polyester including carboxyl end groups is produced by ≧1.03 mol to ≦1.90 mol carboxyl groups or carboxyl-group equivalents of an acid component being employed per mol hydroxyl groups of an alcohol. The polyester polyols obtained, including secondary hydroxyl end groups, can be used for the purpose of producing polyurethane polymers.