Basecoat Neutralization with Inorganic Salts for Allophanate Formation

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Solution Overview

Problem

Uretdione-based clear coats face challenges when applied over pigmented basecoats due to the acidic nature of the basecoats, which hinders the conversion of uretdione and polyol to allophanate groups at ambient or low temperatures, even with tertiary amine catalysts.

Innovation Solution

The approach involves neutralizing the polyol and basecoat using an epoxy or carbodiimide and an inorganic salt, respectively, to minimize acidity and promote the cross-linking of polyuretdione resins with neutralized polyols in the presence of a tertiary amine catalyst, facilitating the formation of allophanate polymers at ambient or low temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If uretdione-based clear coats are applied over pigmented basecoats without neutralization, then the coating process is simple, but the conversion of uretdione and polyol to allophanate groups is hindered due to acidic conditions

Engineering Contradiction:

Improvecoating process simplicityVSAvoidconversion rate of uretdione and polyol to allophanate groups

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The basecoat is pre-neutralized with inorganic salts (such as zinc, calcium, or aluminum salts) before applying the clear coat. This preliminary neutralization action removes acidic groups from the basecoat surface, creating a favorable environment for subsequent allophanate formation when the clear coat is applied, thereby resolving the contradiction between process simplicity and conversion efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Inorganic salts serve as intermediary substances between the acidic basecoat and the uretdione-based clear coat. These salts neutralize the acidity of the basecoat without interfering with the curing mechanism of the clear coat, enabling the conversion of uretdione and polyol to allophanate groups while maintaining process simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If polyol is neutralized with epoxy or carbodiimide at elevated temperatures, then acidity is reduced to promote allophanate formation, but the process complexity and energy consumption increase

Engineering Contradiction:

Improveconversion rate to allophanate groupsVSAvoidenergy consumption for polyol neutralization

Core Design Contradiction:

ProductivityVSUse of energy by stationary object

Solution Approach 1:

Instead of using energy-intensive thermal neutralization of polyol, the invention converts the harmful acidity of the basecoat into a beneficial neutralized surface through inorganic salt treatment. This approach achieves the same goal of promoting allophanate formation while avoiding additional energy consumption, as the neutralization occurs at ambient or curing temperatures without requiring separate heating steps

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Temperature

If inorganic salts are used to neutralize basecoat, then the conversion of uretdione to allophanate at ambient or low temperatures is significantly improved, but the system complexity increases due to additional neutralization steps

Engineering Contradiction:

Improvecuring temperature for allophanate formationVSAvoidnumber of neutralization steps

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The neutralization function is merged into the basecoat formulation itself, where inorganic salts are incorporated during basecoat manufacturing rather than requiring separate neutralization steps. This integration allows the basecoat to self-neutralize upon application, enabling low-temperature allophanate formation while avoiding additional process steps and maintaining system simplicity

Inventive Principle:

Principle #5Merging (Combining)

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 method enhances the conversion rate of uretdione and polyol to allophanate groups, improving the physical properties of the resulting polymers, which can be used to create coatings, adhesives, castings, and sealants with improved chemical resistance.

Implementation Method 1

The polyol may be neutralized by reaction with an epoxy or cabodiimide

Methodology Applied

Scientific EffectNeutralization reaction: Chemical Bonding

Implementation Method 2

The basecoat may be neutralized by complex formation with an inorganic salt

Methodology Applied

Scientific EffectComplex formation: Chemical Bonding

Implementation Method 3

crosslinking polyuretdione resins with neutralized polyols in the presence of a tertiary amine catalyst

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentUS10731051B2Basecoat acid neutralization through inorganic salts

Publication Date: 2020.08.04 COVESTRO LLC

AI summary

The present invention provides a system comprising an allophanate composition comprising a neutralized polyol, a polyuretdione resin, a tertiary amine catalyst, an additive package, and a reducer; and a neutralized basecoat comprising an inorganic salt and a pigment. The present invention further provides a method of making an allophanate system comprising combining a neutralized polyol with a polyuretdione resin in the presence of a tertiary amine catalyst, an additive package, and a reducer to produce an allophanate composition, and contacting the allophanate composition with a neutralized basecoat comprising an inorganic salt and a pigment. The system may be used to make coatings, adhesives, castings, composites, and sealants in which clear-coating on neutralized pigmented basecoats is much improved in comparison to coating on non-neutralized basecoats.