Segmented Polyester Resins for Metal Coatings
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Solution Overview
Problem
Conventional polyester resins lack the balance of impact resistance and adhesion required for coating films on substrates that undergo postforming, deep-drawing, bending, chipping, or impact, as they are either too flexible and soft or too hard and brittle.
Innovation Solution
The development of polyester resins with a combination of 'hard' and 'soft' segments, achieved by using specific acid-functional and hydroxy-functional monomers, which are processed through conventional polyesterification methods to create a material with both elasticity and hardness, suitable for use in coatings that require flexibility and resistance to mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyester resins are made from flexible monomers to improve impact resistance and adhesion, then the resin becomes too soft and lacks hardness
Solution Approach 1:
The polyester resin is segmented into hard segments (from aromatic acids like isophthalic acid and rigid diols like 1,4-cyclohexanedimethanol) and soft segments (from aliphatic acids like adipic acid and flexible diols like 1,6-hexanediol). This segmentation allows the resin to contain both hard and soft regions, achieving a balance between hardness and impact resistance.
Solution Approach 2:
The invention creates a composite polyester resin structure by combining monomers with different properties. The resin contains both aromatic (hard) and aliphatic (soft) components, forming a composite material that exhibits both hardness and flexibility, resolving the contradiction between these two properties.
2Temperature
If polyester resins are made from hard monomers to improve hardness and chemical resistance, then the resin becomes too brittle and loses impact resistance
Solution Approach 1:
The polyester resin is segmented into hard segments (from aromatic acids like isophthalic acid and rigid diols like 1,4-cyclohexanedimethanol) and soft segments (from aliphatic acids like adipic acid and flexible diols like 1,6-hexanediol). This segmentation allows the resin to contain both hard and soft regions, achieving a balance between hardness and impact resistance.
Solution Approach 2:
The invention creates a composite polyester resin structure by combining monomers with different properties. The resin contains both aromatic (hard) and aliphatic (soft) components, forming a composite material that exhibits both hardness and flexibility, resolving the contradiction between these two properties.
3Reliability
If the mass fraction of higher functional acid educts is increased to improve crosslinking, then the resin becomes too brittle and loses flexibility
Solution Approach 1:
The invention optimizes the parameter of higher functional acid content by limiting it to a specific range (0.1-5 mass%). This parameter control ensures sufficient crosslinking for adhesion while preventing excessive crosslinking that would cause brittleness, thus balancing adhesion and impact resistance.
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 resulting polyester resins exhibit excellent adhesion, impact resistance, and chemical and mechanical resistance, making them suitable for various substrates and applications, including metal coatings where they demonstrate quick development of hardness and resilience.
Implementation Method 1
Reacting acids and alcohols entails formation of water and of the desired polyester, in a condensation process
Implementation Method 2
Polyesters are generally prepared from polyfunctional acids, particularly carboxylic acids, and polyfunctional hydroxy compounds, particularly alcohols or phenols, in a condensation or polyesterification process
Implementation Method 3
Polyesters can also be prepared by ring-opening polyaddition of cyclic esters (lactones)
Implementation Method 4
or by reacting more reactive derivatives of the said acids and hydroxy compounds, such as acid halides, acid anhydrides, or esters of acids with volatile alcohols such as methanol, or esters of acids with enols such as isopropenyl alcohol that form aldehydes or ketones upon transesterification
Implementation Method 5
These polyesters are preferably of low molar mass, and can be cured by radically initiated polymerisation, which may be induced thermally, by heating or, by exposure to high energy such as UV light or other radiation
Data Source
AI summary
The invention relates to a polyester AB comprising moieties derived from di- or polyfunctional organic acid compounds A and moieties derived from di- or polyfunctional organic hydroxy compounds B, wherein the compounds A comprise "hard" acid compounds Al having two or more acid groups per molecule, and soft acid compounds A2, and the compounds B comprise "hard" hydroxyfunctional compounds Bl having two or more hydroxyl groups per molecule, and soft hydroxyfunctional compounds B2, and coating compositions prepared from these with crosslinkers selected from the group consisting of isocyanates, capped isocyanates, aminoplast crosslinkers, and phenoplast crosslinkers, as well as their application in coating of metal substrates.