Waterborne PSA with Polymodal Particle Size Distribution
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Solution Overview
Problem
Waterborne acrylic-based pressure sensitive adhesive compositions face challenges in achieving high solids content greater than 65 wt % while maintaining low viscosity and preventing coagulation and britteness, which are essential for coating technologies like curtain coating to reduce transportation costs and improve coating rheology.
Innovation Solution
A water-based pressure-sensitive adhesive composition with a polymodal particle size distribution, comprising a first and a second acrylic-based polymer with specific glass transition temperatures and molecular weights, and a surfactant, which allows for a solids content of at least 65.5 wt % without the need for thickeners and maintains viscosity below 650 cps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the solids content in the waterborne PSA composition is increased to decrease transportation costs and improve coating rheology, then the viscosity of the PSA increases and the risk of coagulation and britteness increases
Solution Approach 1:
The patent applies segmentation by using a polymodal particle size distribution with multiple distinct size ranges (first mode: 80-180 nm, second mode: 200-400 nm, third mode: 450-800 nm). This divides the particle population into different size segments that collectively provide low viscosity while maintaining high solids content, resolving the contradiction between quantity of substance and harmful viscosity increase.
Solution Approach 2:
The patent changes the particle size distribution parameters by defining specific modal ranges and a controlled polydispersity index (0.5-2.0). This parameter optimization allows the composition to achieve ≥65.5 wt% solids content while keeping viscosity below 650 cps, directly addressing the contradiction between solids content and viscosity.
2Use of energy by stationary object
If the solids content in the waterborne PSA composition is increased to minimize drying energy, then the risk of coagulation and britteness in the resultant PSA dry layer increases
Solution Approach 1:
The segmented particle size distribution (multiple modes at 80-180 nm, 200-400 nm, and 450-800 nm) prevents coagulation by maintaining adequate spacing between particles during drying. This segmentation allows high solids content to be achieved without increasing coagulation risk, enabling minimal drying energy while maintaining reliability.
Solution Approach 2:
The patent creates a composite particle system with diverse size distributions and two different polymers (A and B). This composite structure provides both the high solids content needed to minimize drying energy and the structural integrity to prevent coagulation and britteness, resolving the contradiction between energy efficiency and reliability.
3Productivity
If a waterborne PSA composition with greater than 65 wt % solids content is developed, then transportation costs decrease and coating rheology improves, but the viscosity increases
Solution Approach 1:
The polymodal particle size distribution segments the particle population into three size modes, which reduces interparticle interactions and maintains low viscosity. This allows the composition to achieve ≥65.5 wt% solids content with viscosity <650 cps, resolving the contradiction between transportation efficiency and ease of operation.
Solution Approach 2:
The patent optimizes particle size parameters by defining specific modal ranges and controlling the polydispersity index (0.5-2.0). This parameter control enables high solids content to be achieved while maintaining operational ease through low viscosity, directly resolving the contradiction between productivity and ease of operation.
Data Source
AI summary
The present disclosure is directed to a water-based adhesive composition. In an embodiment, the water-based pressure-sensitive adhesive composition includes a plurality of particles having a polymodal particle size distribution. The particles are composed of (A) a first polymer, and (B) a second polymer different than the first polymer. The particles have a d50 greater than 450 nm and a polydispersity index, PDi, from 0.5 to 2.0. (C) The composition has a solids content greater than or equal to 65.5 wt %. Further disclosed are articles with the water-based pressure-sensitive adhesive composition.