Binder-Deficient Slip Coating for Polymer Film Handling
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Solution Overview
Problem
Polymer films face challenges in handling due to strong adhesion when surfaces are too smooth or slippery, leading to issues like blocking and telescoping, which can result in reduced yields and increased costs, especially when particle-filled layers are used to improve surface roughness.
Innovation Solution
A novel polymeric sheet construction featuring a core member with a slip control layer comprising a footing layer, a binder layer, and an array of particles protruding from the binder layer, where the particles' average diameter is greater than the combined thickness of the footing and binder layers, allowing for improved handling properties with minimal binder polymer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If particle-filled layers are applied to increase surface roughness, then handling properties improve, but binder polymer usage increases and cost increases
Solution Approach 1:
The invention changes the particle size parameter to be larger than previously used, with particles ranging from 1-50 microns and preferably 5-20 microns. These larger particles provide adequate handling properties with minimal binder polymer (0.1-5 weight percent), resolving the contradiction between improvement in handling and reduction in binder usage
Solution Approach 2:
The invention applies particles only to the outermost surface layer (0.1-10 microns thick) rather than throughout the entire film structure. This localized application provides the necessary surface roughness for handling while minimizing the total quantity of binder polymer required
2Manufacturing precision
If surfaces are made too smooth, then manufacturing precision improves, but handling becomes difficult due to strong adhesion and blocking
Solution Approach 1:
The invention creates a dual-nature surface structure where the bulk film maintains smoothness for manufacturing precision while the outermost layer (0.1-10 microns) contains particles that provide roughness for handling ease. This local differentiation resolves the contradiction between smooth surfaces and easy handling
Solution Approach 2:
The invention creates a composite surface structure combining a smooth base film with a particle-containing outer layer. This composite approach allows the film to exhibit both smoothness (for manufacturing) and controlled roughness (for handling) simultaneously
3Reliability
If binder polymer quantity is increased to hold particles, then particle adhesion improves, but cost increases and handling properties worsen due to excessive slip
Solution Approach 1:
The invention optimizes the binder polymer concentration to a minimal range of 0.1-5 weight percent, which is sufficient to hold particles securely without creating excessive slip. This parameter optimization resolves the contradiction between adequate adhesion and proper handling characteristics
Solution Approach 2:
The binder polymer is concentrated in the outermost particle-containing layer rather than distributed throughout the entire film. This localized concentration provides sufficient particle adhesion while minimizing overall binder content and associated slip issues
Data Source
AI summary
A sheet comprising: (1) a core member comprising one or more layers and having a first major surface and (2) a slip control layer disposed on at least a portion of the first major surface, wherein the slip control layer comprises: (i) a footing layer disposed on at least a portion of the first major surface of the core member, (ii) a binder layer disposed on the footing layer, and (iii) an array of particles disposed in the binder layer and footing layer and protruding therefrom, wherein the average diameter of the particles is greater than the combined thickness of the foot layer and binder layer. A process for making such a sheet comprising: (1) providing a core member; (2) forming a footing layer on at least a portion of the first major surface of the core member, wherein the footing layer is viscoelastic and has a Tg that is lower than either the Tg or the Tm of the polymer at the first major surface of the core member; (3) applying a binder layer composition comprising a film forming polymer and particles to the surface of the footing layer; then (4) tentering the assembly under sufficient heat to soften the footing layer such that the particles sink into the footing layer, wherein the average diameter of the particles is greater than the combined thickness of the footing layer and binder layer.