Compositions containing high melt index ethylene/alpha-olefin multi-block interpolymers
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Solution Overview
Problem
Existing adhesive compositions face a challenge in achieving low viscosity while maintaining or improving adhesive properties such as loop tack and peel strength, as reducing polymer viscosity or content often deteriorates mechanical strength and cohesive strength.
Innovation Solution
A composition comprising ethylene/alpha-olefin multi-block interpolymers with specific properties, including a melt index of ≥ 30 dg/min, a molar ratio of alpha-olefin in soft segments to hard segments ≥ 18, and a weight ratio of soft segments to hard segments ≤ 12.0, along with a tackifier and/or oil, to enhance adhesive performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the viscosity or molecular weight of the polymer component is reduced, then the final adhesive viscosity is reduced, but the mechanical strength and cohesive strength of the adhesive deteriorate
Solution Approach 1:
The polymer is segmented into hard blocks and soft blocks with distinct functions. Hard blocks (20-45 wt%) provide mechanical strength and cohesive strength through crystallinity, while soft blocks (55-80 wt%) provide low viscosity and processability. This segmentation allows the adhesive to simultaneously achieve low viscosity and high strength by distributing these properties to different segments of the polymer structure.
2Force
If the content of the polymer component is reduced, then the final adhesive viscosity is reduced, but the mechanical strength and cohesive strength of the adhesive deteriorate
Solution Approach 1:
The invention changes the parameters of the polymer component specifically by controlling the melt index (I2 ≥ 30 dg/min) and the composition ratio of hard to soft blocks (weight ratio ≤ 12.0). These parameter changes allow the polymer to provide adequate strength at lower concentrations while maintaining low adhesive viscosity, as the optimized hard block content (20-45 wt%) ensures sufficient mechanical properties even when polymer content is reduced.
3Strength
If high density or high hard segment content is increased, then the crystallinity of the adhesive composition is increased, but the tackiness of the composition decreases
Solution Approach 1:
The invention optimizes the parameter of hard segment content to a specific range (20-45 wt%) rather than maximizing it. This parameter change balances crystallinity and tackiness: sufficient hard segments provide the desired crystallinity and strength, while the limited amount (not excessive high content) preserves adequate tackiness for adhesive performance. The melt index parameter (I2 ≥ 30 dg/min) is also controlled to ensure proper flow and tackiness.
Solution Approach 2:
The adhesive composition has local quality differentiation between hard blocks and soft blocks. Hard blocks provide localized crystallinity and strength in specific regions, while soft blocks provide localized tackiness and adhesion in other regions. This local quality distribution allows the overall composition to simultaneously achieve crystallinity and tackiness without one property compromising the other.
Data Source
AI summary
A composition comprising the following: a) at least one ethylene/alpha-olefin multi-block interpolymer that comprises soft segments (SS) and hard segments (HS), and wherein the interpolymer comprises the following properties: i) a melt index (I2) ≥ 30 dg/min, ii) a molar ratio of "the alpha-olefin in the SS" to "the alpha-olefin in the HS" ≥ 18, iii) a weight ratio of the SS to the HS ≤ 12.0; at least one tackifier and/or at least one oil.