Solventborne Primer Adhesion via Silane-Oligoester Crosslinking
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Solution Overview
Problem
The adhesion between primer surfacer and topcoat, as well as between primer surfacer and substrate, in solventborne paint systems used for utility vehicles and automotive refinish is inadequate, particularly when cured at moderate temperatures, leading to delamination issues.
Innovation Solution
A solventborne primer surfacer is developed containing an alpha,omega-hydroxy-functionalized oligoester and an alkoxysilane additive, where at least 90 mol% of the oligoester's OH groups are reacted with the alkoxysilane, enhancing the adhesion properties by improving the chemical bonding between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solventborne primer surfacer systems are used, then the paint system can be applied and cured at moderate temperatures, but the adhesion between primer surfacer and topcoat, as well as between primer surfacer and substrate, is inadequate
Solution Approach 1:
The patent modifies the chemical composition parameters of the primer surfacer by incorporating specific silane additives (gamma-glycidyloxypropyltrimethoxysilane and/or gamma-methacryloxypropyltrimethoxysilane) at controlled concentrations (0.1-5 wt%). This chemical parameter change enables the system to achieve reliable adhesion at moderate curing temperatures (60-100°C) that would otherwise be insufficient for conventional systems.
Solution Approach 2:
The patent creates a composite primer surfacer system by combining conventional solventborne resin components with organosilane additives. This composite formulation integrates the adhesion-promoting properties of silanes with the film-forming capabilities of traditional paint resins, achieving both moderate temperature curing and improved adhesion simultaneously.
2Adaptability or versatility
If the primer surfacer is cured at moderate temperatures to accommodate fully assembled automobiles, then the painting process is feasible for refinish applications, but the adhesion between coats deteriorates
Solution Approach 1:
The patent adjusts the chemical reactivity parameters of the curing system by selecting silane compounds with appropriate functional groups (glycidyl and methacryloxy) that can cure effectively at lower temperatures. This parameter optimization maintains versatility for refinish applications while preventing adhesion deterioration.
Solution Approach 2:
The silane additives act as intermediary substances that facilitate bonding between the primer surfacer and subsequent coats (basecoat/clearcoat). These intermediary compounds create chemical bridges that enable adhesion under the constrained temperature conditions required for refinish work on assembled vehicles.
3Ease of manufacture
If conventional primer surfacer formulations are used, then the formulation is simple and cost-effective, but delamination occurs after weathering exposure
Solution Approach 1:
The patent develops a composite formulation that combines conventional paint ingredients with specific silane additives. This composite approach maintains the ease of manufacture associated with traditional formulations while incorporating weathering-resistant properties through the silane components that form durable adhesive bonds.
Solution Approach 2:
The silane additives provide beforehand cushioning by creating a chemically robust adhesive interface before weathering exposure occurs. This preventive measure ensures that the paint system maintains adhesion integrity when subsequently exposed to environmental weathering conditions.
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 additive significantly improves the adhesion between the primer surfacer and adjacent coats, including the substrate, even after exposure to weathering, reducing delamination and enhancing the durability of the paint system.
Implementation Method 1
reacting (a) at least one alpha,omega-hydroxy-functionalized oligoester... and (b) at least one alkoxysilane... with the proviso that at least 90 mol % of all the OH groups of the alpha,omega-hydroxy-functionalized oligoester have been reacted with an OH-reactive functional group A
Implementation Method 2
A solventborne primer surfacer which comprises at least one additive preparable by reacting... at least one alkoxysilane of the structural formula (II)... enhancing the adhesion properties by improving the chemical bonding between layers
Data Source
AI summary
The present invention relates to a solventborne primer surfacer which comprises at least one additive preparable by reacting at least one alpha,omega-hydroxy-functionalized oligoester which possesses an OH number of 30 to 160 mg KOH/g, a theoretical carbon-carbon double bond content of 1 to 2.5 mmol/g, a number-average molecular weight of 1000 to 3000 g/mol, and a weight-average molecular weight of 2800 to 10 000 g/mol, and at least one alkoxysilane which possesses an OH-reactive functional group, the sum of the weight percentage fractions of all additives of the invention being 0.5 to 10 wt %, based on the total amount of the solventborne primer surfacer. The present invention further relates to a process for producing multicoat paint systems, and to multicoat paint systems producible by means of said process. The invention further relates to the use of the additive identified above in solventborne primer surfacers for improving adhesion.