Plaster Primer Coating Composition for Low Water Absorption

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Solution Overview

Problem

Commercially available plaster or bonding primers exhibit high water absorption, require surfactants for storage stability, and often necessitate large quantities of water glass for fire safety, leading to high pH values and labeling requirements.

Innovation Solution

A coating composition comprising a bimodal filler combination of fine and ultrafine fillers, a siloxane-based hydrophobing agent, and limited water glass, without wetting and dispersing agents, defoamers, waxes, matting agents, film-forming aids, and deaerators, to achieve reduced water absorption and improved fire protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If surfactants such as wetting and dispersing agents are added to ensure storage stability, then storage stability is improved, but water absorption increases

Engineering Contradiction:

Improvestorage stabilityVSAvoidwater absorption

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent removes surfactants (wetting and dispersing agents) from the primer composition entirely, achieving storage stability through alternative means - specifically through the synergistic combination of polymer emulsion selection, filler composition (bimodal distribution), and controlled water glass content, thereby eliminating the harmful effect of increased water absorption

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes key composition parameters: using polymers with specific glass transition temperatures (-10°C to 0°C), controlling filler particle size distribution (bimodal with D10, D50, D90 values), and limiting water glass to 1-10% by weight, which together enable stability without surfactants

Inventive Principle:

Principle #35Parameter changes

2Reliability

If large quantities of water glass are added to achieve adequate fire safety, then fire protection is improved, but pH value increases leading to labeling requirements

Engineering Contradiction:

Improvefire protectionVSAvoidpH value

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes water glass content to a specific range (1-10% by weight) and combines it with polymers having controlled glass transition temperatures and specific filler compositions, achieving fire protection (PCS value ≤ 2.0 MJ/kg) while maintaining pH below 12, thus avoiding special labeling requirements

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite system combining polymer emulsion, water glass, bimodal filler distribution, and specific additives that work synergistically to provide fire protection through the PCS value control while managing pH levels through the overall composition balance

Inventive Principle:

Principle #40Composite materials

3Strength

If conventional primer compositions are used to provide adhesion promotion, then adhesion between substrate and coating is improved, but water absorption increases leading to moisture penetration

Engineering Contradiction:

ImproveadhesionVSAvoidmoisture penetration

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent uses polymers with specific glass transition temperatures (-10°C to 0°C) to maintain flexibility and adhesion while controlling water absorption, combined with bimodal filler distribution and limited water glass content to create a matrix that adheres well to substrates like mineral wool insulation boards while resisting moisture penetration

Inventive Principle:

Principle #35Parameter changes

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 composition provides storage-stable, low water absorption, and adequate fire protection without surfactants, enabling wider application range and reduced environmental and health hazards.

Implementation Method 1

a siloxane-based hydrophobing agent

Methodology Applied

Scientific EffectHydrophobe: Hydrophobe

Implementation Method 2

adequate fire protection

Methodology Applied

Scientific EffectFire resistance:

Data Source

PatentEP4660260A1Coating composition for plaster primer or bonding primer

Publication Date: 2025.12.10 STO SE & CO KGAA

AI summary

The present invention relates to a coating composition comprising at least one organic polymer binder, at least a bimodal filler combination with at least one fine filler (A) having a median particle size D50 of 5 µm to 20 µm, and at least one ultrafine filler (B) having a median particle size D50 of 0.5 µm to less than 5 µm, a siloxane-based hydrophobing agent, water glass in an amount of at most 1.5 wt.%, based on the solids content of the water glass and the total weight of the coating composition, and water, wherein the coating composition is substantially free of wetting and dispersing agents, defoamers, waxes, matting agents, film-forming aids and deaerators.The invention further relates to a surface coating obtainable or obtained by means of the coating composition and the use of the surface coating as a plaster base, bonding agent or as a protective layer.