Self-Crosslinkable Latex Particles for Stable Coatings

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Solution Overview

Problem

There is a need for an aqueous latex composition that remains stable during storage while allowing self-crosslinking to occur under ambient conditions after application, without the use of excessive waterborne crosslinking agents, to improve film strength and water resistance in waterborne coatings.

Innovation Solution

The composition includes latex particles polymerized from acrylic and/or vinyl acrylic monomers with diacetone acrylamide or methacrylamide moieties that crosslink when water is depleted, using a small amount of adipic dihydrazide as a crosslinking agent, allowing self-crosslinking to occur without premature reactions during storage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional crosslinking agents like adipic dihydrazide are used in aqueous latex compositions, then film strength and water resistance are improved, but premature crosslinking reactions occur during storage reducing shelf stability

Engineering Contradiction:

Improvefilm strengthVSAvoidshelf stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent incorporates crosslinking moieties (diacetone acrylamide and methacrylamide) directly into the latex particles during polymerization as preliminary preparation. These moieties remain dormant during storage and only become active when water is depleted during film formation, thus preventing premature crosslinking while ensuring crosslinking capability when needed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the physical-chemical parameters of the crosslinking system by using moisture-curing chemistry. The crosslinking reaction is triggered by the parameter change of water depletion during drying, rather than occurring in the presence of water during storage. This parameter change approach allows the composition to remain stable during storage but crosslink effectively during film formation.

Inventive Principle:

Principle #35Parameter changes

2Strength

If waterborne crosslinking agents are used to improve film properties, then mechanical properties are enhanced, but the use of volatile organic compounds and odor issues increase

Engineering Contradiction:

Improvemechanical propertiesVSAvoidodor and VOC emissions

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent uses water as the medium for the crosslinking reaction instead of traditional organic crosslinking agents. Water evaporates completely during drying, leaving no harmful residues, odors, or VOC emissions. The water serves its crosslinking function and then disappears, analogous to disposable short-living objects that fulfill their purpose and vanish.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes chemical crosslinking agents (which would introduce VOCs and odors) with a physical-chemical process driven by water depletion. The crosslinking is achieved through the evaporation of water and subsequent reaction between exposed functional groups, replacing the need for harmful chemical additives.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If crosslinking reactions occur during storage, then film strength is improved, but intra particle crosslinking under ambient drying conditions is reduced

Engineering Contradiction:

Improvefilm strengthVSAvoidcrosslinking efficiency under ambient conditions

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The patent creates local quality differences within the latex particles by incorporating specific crosslinking moieties (diacetone acrylamide and methacrylamide) that have different reactivities. These moieties are positioned and structured within the particles to remain dormant during storage but become highly reactive when water is depleted during ambient drying, thus optimizing both storage stability and subsequent crosslinking efficiency.

Inventive Principle:

Principle #3Local quality

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 approach enhances the mechanical and chemical properties of the paint film, such as scrub resistance, water resistance, and shelf stability, while minimizing the use of volatile organic compounds and odor issues associated with conventional crosslinking agents.

Implementation Method 1

the latex particles crosslink when the water content is reduced or substantially depleted under ambient conditions by drying or evaporation

Methodology Applied

Scientific EffectCrosslinking reaction: Chemical Bonding

Implementation Method 2

when the water content is reduced or substantially depleted under ambient conditions by drying or evaporation

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS9394460B1Ambient self-crosslinkable latex

Publication Date: 2016.07.19 COLUMBIA INSURANCE CO

AI summary

The present invention relates to storage stable film forming latex particles that crosslink under ambient conditions during or after drying. Monomers for the formation of the crosslinkable moieties in the latex particles include diacetone acrylamide (DAAM) or the likes and methacrylamide (MAM) or the likes with or without styrene. A paint composition comprising the storage stable latex particles that may include a small amount or crosslinking agent such as adipic acid dihydrazide (ADH) in the aqueous phase is also described.