Block Copolymer Additives for Coating Flow and Defect Control
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Solution Overview
Problem
Existing polymer-based liquid coating systems with high surface tension pose challenges in application to surfaces with low surface tension, often resulting in uneven coatings and defects due to the high intrinsic surface tension of modern synthetic binder systems, which are not effectively addressed by conventional additives that may cause foaming, incompatibility, or loss of gloss.
Innovation Solution
Development of block copolymers with a polydimethylsiloxane block and ethylenically unsaturated monomer blocks, which are easy to prepare and have a high graft polymer fraction, acting as efficient flow control assistants and dirt-repelling additives by reducing surface tension and enhancing compatibility with synthetic binder systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional additives (poly(meth)acrylic esters, polysiloxanes, waxes, fluorinated resins) are used to reduce surface tension and improve flow, then spreading and flow are enhanced, but foaming, foam stabilization, incompatibility, haze, gloss loss, migration problems, and coating stability issues occur
Solution Approach 1:
The invention uses block copolymers comprising a polydimethylsiloxane block and a polymer block composed of ethylenically unsaturated monomers. This composite structure combines the surface tension-reducing properties of polysiloxane with the compatibility and stability of polymer blocks, eliminating the harmful side effects of conventional additives while maintaining flow control functionality.
Solution Approach 2:
The invention changes the molecular structure parameter by using block copolymers with specific architectures (central polysiloxane block with polymer blocks formed from polymerized ethylenically unsaturated monomers). This structural parameter change enables the additive to reduce surface tension without causing foaming or incompatibility issues associated with conventional additives.
2Reliability
If modern synthetic binder systems (epoxy resins, polyurethane systems, polyester resins, melamine resins, radiation-curing binders) are used, then coating performance is improved, but intrinsic surface tension increases making application to low surface tension substrates difficult
Solution Approach 1:
The block copolymer acts as an intermediary substance between the high surface tension synthetic binder system and the low surface tension substrate. The polysiloxane block reduces the overall surface tension of the coating composition, enabling wetting and adhesion to substrates that would otherwise be incompatible with high-performance synthetic binders.
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 block copolymers promote smooth, uniform coatings with reduced cratering and water repellency, making them suitable for use in liquid systems based on epoxy resins, polyurethane systems, and radiation-curing binders, while minimizing defects and improving the stability of the coating composition.
Implementation Method 1
These flow control assistants, by reducing the surface tension of the composition, bring about improved spreading of the composition over the surface of the substrate
Implementation Method 2
The block copolymers promote smooth, uniform coatings with reduced cratering and water repellency
Data Source
AI summary
The present invention relates to novel block copolymers of general formula (I). The invention further relates to a method for producing such block copolymers and to the use of such block copolymers, particularly as additives in liquid coating-agent compositions. A{X—[O—C(O)NH—Y—NH—C(O)—O-M-B]k}n (I). In formula (I), the variables have the following meanings: n is a number in the range from 1 to 40 or 2 to 40, particularly 1 to 10 or 2 to 10 and especially 2 to 5; k is 1 or 2; A is a poly(dimethylsiloxane) block; B is a polymer block constructed of ethylenically unsaturated monomers, which optionally comprises a terminal group different from hydrogen; X is a bivalent or trivalent group having 2 to 20 C atoms, which is saturated or unsaturated and which optionally bears 1, 2, 3, or 4 substituents selected from among OH, COOH, CONH2, C1-C4 alkoxy, C1-C4 alkoxycarbonyl, and halogen; Y is a bivalent hydrocarbon group having 2 to 20 C atoms, which is saturated or unsaturated, and M is a chemical bond or C2-C10 alkylene, which can be interrupted by one or two groups not directly adjacent, selected from among O, C(═O)O, and (C═O)NH and which optionally bears 1, 2, 3, or 4 substituents selected from among OH, COOH, CONH2, C1-C4 alkoxy, C1-C4 alkoxycarbonyl, and phenyl.