Branched Block Copolymer Elastic Material for Diaper Films
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Solution Overview
Problem
Styrenic block copolymers used in elastic composites for products like diapers are difficult to process due to their high viscosity, which hinders their formation into films with good elastic performance.
Innovation Solution
A nonwoven web material with a crosslinked network containing a branched block copolymer having a monoalkenyl aromatic midblock between conjugated diene endblocks, which is formed through melt extrusion and crosslinking, allowing for improved processability and elastic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional styrenic block copolymers (S-B-S) are used to form elastic films, then good elastic performance can be achieved, but the high viscosity makes them difficult to process
Solution Approach 1:
The patent changes the molecular architecture parameter from linear S-B-S to branched B-S structure with monoalkenyl aromatic midblock and conjugated diene endblocks. This structural parameter change reduces viscosity while maintaining elastic performance, resolving the contradiction between processability and elastic reliability
Solution Approach 2:
The patent creates a composite material system combining branched block copolymer with crosslinking agents to form a crosslinked network. This composite approach enables low-viscosity processing of the copolymer while the crosslinked network provides the required elastic performance and structural integrity
2Strength
If the polymer is crosslinked to improve elastic performance, then strength and elasticity increase, but the processing complexity increases
Solution Approach 1:
The patent performs preliminary crosslinking of the copolymer before final product formation. The copolymer is crosslinked to form a gel structure that provides elastic strength, while this pre-crosslinked structure can then be easily formed into the desired final product shape, reducing overall processing complexity
Solution Approach 2:
The patent utilizes phase transition of the copolymer from sol to gel state during crosslinking. This phase transition allows the material to transform from a processable liquid state to a structured gel state with elastic properties, enabling strength development without excessive processing complexity
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 resulting material exhibits enhanced strength and elasticity with fewer 'dangling' styrene chains, providing better elastic performance and processing ease compared to conventional styrenic block copolymers.
Implementation Method 1
a crosslinked network containing a branched block copolymer having a monoalkenyl aromatic midblock positioned between conjugated diene endblocks
Implementation Method 2
melt extruding a branched block copolymer having a monoalkenyl aromatic midblock positioned between conjugated diene endblocks; forming a precursor elastic material from the melt extruded copolymer
Data Source
AI summary
An elastic material for use in an absorbent article is provided. The elastic material contains a crosslinked network formed from a branched block copolymer having a monoalkenyl aromatic midblock positioned between conjugated diene endblocks (e.g., butadiene-styrene-butadiene (“B-S-B”) triblock copolymer). Prior to crosslinking, the branched block copolymers have a relatively low viscosity and thus may be readily formed into a precursor elastic material (e.g., film, strands, web, etc.) that is subsequently crosslinked to achieve the desired elastic and mechanical properties. Crosslinking is typically achieved through the formation of free radicals (unpaired electrons) that link together to form a plurality of carbon-carbon covalent bonds at the conjugated diene endblocks.