Copolymer Latex Particle Size Control for Adhesion and Viscosity
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Solution Overview
Problem
Existing copolymer latexes with small particle sizes for use as binders face challenges in achieving both high adhesion strength and low viscosity, which are essential for practical applications, particularly in coating compositions and electrochemical devices, due to limitations in handling properties and compatibility with fillers.
Innovation Solution
A copolymer latex with a specific composition comprising 20-80% aliphatic conjugated diene monomer, 4-15% unsaturated carboxylic acid monomer, and 5-76% other copolymerizable monomers, with a number average particle size of 30-80 nm and viscosity of 50-400 mPa·s, is developed, incorporating structural units from α, β-unsaturated nitrile and aromatic vinyl compounds to enhance adhesion and handling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the particle size of copolymer latex is reduced to improve adhesion strength, then the effective adhesion area between filler and copolymer particles increases, but the viscosity becomes extremely high making it difficult to handle at practical concentration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size within the range of 30-80 nm and adjusting the monomer composition ratios (conjugated diene: 20-80%, unsaturated carboxylic acid: 4-15%, other copolymerizable: 5-76%). This optimization resolves the contradiction by finding the optimal particle size range that provides sufficient adhesion strength while maintaining acceptable viscosity for handling.
Solution Approach 2:
The patent uses composite materials by creating a copolymer system combining three types of monomers with specific functional properties. The conjugated diene provides adhesion, the unsaturated carboxylic acid contributes to particle stability and reactivity, and the other copolymerizable monomers adjust the overall properties. This composite approach allows balancing adhesion strength and handling properties.
2Ease of operation
If a large amount of viscosity reducing agent is used to improve handling properties, then the viscosity is reduced, but the water resistance deteriorates
Solution Approach 1:
The patent changes the fundamental parameter approach by not relying on viscosity reducing agents at all. Instead, it achieves acceptable handling properties through intrinsic particle size control (30-80 nm) and optimized monomer composition, particularly the balance between conjugated diene (20-80%) and other copolymerizable monomers (5-76%). This eliminates the need for viscosity reducers and preserves water resistance.
3Strength
If the particle size is made small to improve adhesion strength, then the effective adhesion area increases, but the printing strength and blister resistance cannot be improved simultaneously without additional surfactant
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size to 30-80 nm and carefully controlling the monomer composition, particularly the ratio of conjugated diene (20-80%) to other copolymerizable monomers (5-76%). This inherent optimization provides both adhesion strength and durability without requiring additional surfactants that would compromise printing strength and blister resistance.
Data Source
AI summary
To provide a copolymer latex having a small particle size, which has a sufficient adhesion strength as a binder and a low viscosity and excellent handling properties in a composition containing a filler and the like, a composition for coating paper using the copolymer latex, and a coated paper having a coating layer formed by the composition.A copolymer latex contains a copolymer comprising: (A) 20 to 80% by mass of a structural unit derived from an aliphatic conjugated diene monomer, (B) 4 to 15% by mass of a structural unit derived from an unsaturated carboxylic acid monomer, and (C) 5 to 76% by mass of a structural unit derived from other copolymerizable monomer, wherein the total of (A), (B) and (C) being 100% by mass, and has a number average particle size of 30 to 80 nm by measurement with a transmission electron microscope, and has a viscosity of 50 to 400 mPa·s at a solid content of 48% by mass.