Defoamer Composition for Aqueous Paints with Shear Resistance
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Solution Overview
Problem
Existing defoamers, particularly silicone-type and compound-type defoamers, face challenges such as bleeding onto the coating film surface, causing cissing or impairing overcoatability, and losing defoaming properties under high-shear conditions, which are detrimental in large-scale coating processes.
Innovation Solution
A defoamer composition for aqueous paints is developed, comprising a nonionic surfactant with a specific hydrophilic moiety and HLB range, a polymer without hydrophilic moieties but with specific SP value and molecular weight ranges, and organic solid fine particles, which collectively enhance defoaming properties, shear resistance, and maintain overcoatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone-type defoamers are used to achieve excellent foam-breaking properties, then defoaming effect is improved, but silicone component bleeds onto coating film surface causing cissing or impairing overcoatability
Solution Approach 1:
The invention changes the chemical composition parameters by replacing silicone compounds with a specific combination of nonionic surfactant, polymer, and organic solid fine particles. The nonionic surfactant has controlled HLB value (1-16) and the polymer has specific SP value (7.5-12) and molecular weight (400-1,000,000), creating a defoamer that achieves foam-breaking properties without silicone-related cissing and overcoatability problems
Solution Approach 2:
The invention uses a composite defoamer system comprising three distinct components: nonionic surfactant (A), polymer (B), and organic solid fine particles (C). This composite approach combines the foam-breaking capability of surfactants with the stability and shear resistance provided by the polymer and fine particles, achieving effective defoaming without the harmful effects of silicone-type defoamers
2Reliability
If compound-type defoamers with fine particles are used to achieve high defoaming properties, then defoaming effect is improved, but fine particles affect smoothness and gloss of coating film
Solution Approach 1:
The invention carefully controls the particle size parameter of organic solid fine particles (C) to be within 0.1-150 μm, with preferred range of 1-50 μm. This parameter optimization allows the fine particles to provide sufficient defoaming effect while being small enough not to significantly affect coating film smoothness and gloss, resolving the contradiction between defoaming performance and coating quality
3Ease of manufacture
If high shear force is applied during dispersion process to improve functionality, then dispersion is improved, but defoamers lose their defoaming properties due to shear force
Solution Approach 1:
The polymer (B) component with SP value of 7.5-12 and molecular weight of 400-1,000,000 provides structural stability and shear resistance to the defoamer system. This polymer backbone maintains the integrity of the defoamer particles under high shear conditions during dispersion and application, preventing loss of defoaming properties while allowing effective dispersion
Solution Approach 2:
The organic solid fine particles (C) with hydrophobic surfaces provide localized defoaming activity at the air-liquid interface, while the polymer matrix provides bulk stability. This local quality differentiation allows the system to withstand shear forces in the bulk while maintaining defoaming capability at the interface
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 defoamer composition effectively forms a coating film with excellent appearance, exhibits robust shear resistance, and does not impair overcoatability, even under high-shear conditions, thereby addressing the limitations of existing defoamers.
Implementation Method 1
a nonionic surfactant (A) having at least one hydrophilic moiety selected from the group consisting of an ethylene glycol moiety, a polyethylene glycol moiety and a polyhydric alcohol moiety in a molecule, the nonionic surfactant (A) having an HLB of 1 to 16
Implementation Method 2
a polymer (B) which does not have the hydrophilic moiety in a molecule, the polymer (B) having an SP value of 7.5 to 12 and a weight-average molecular weight of 400 to 1,000,000
Implementation Method 3
organic solid fine particles (C) which are in a solid state in the defoamer composition at 25°C
Data Source
AI summary
A defoamer composition which is capable of forming a coating film with excellent coating appearance, has excellent shear resistance, and does not impair overcoatability, an aqueous paint composition containing the defoamer composition, and an article coated with a coating agent containing the defoamer composition are provided. A defoamer composition for aqueous paints contains: a nonionic surfactant (A) having at least one hydrophilic moiety selected from the group consisting of an ethylene glycol moiety, a polyethylene glycol moiety and a polyhydric alcohol moiety in a molecule, the nonionic surfactant (A) having an HLB of 1 to 16; a polymer (B) which does not have the hydrophilic moiety in a molecule, the polymer (B) having an SP value of 7.5 to 12 and a weight-average molecular weight of 400 to 1,000,000; and organic solid fine particles (C) which are in a solid state in the defoamer composition at 25°C.