Block Copolymer Crumb Adhesive Composition
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Solution Overview
Problem
Conventional block copolymers used in pressure-sensitive adhesive compositions face issues with solubility, transportability, melt viscosity, and odor, along with an unsatisfactory balance of these properties.
Innovation Solution
A crumb of block copolymer with specific structural characteristics, including a specific surface area, pore volume, and molecular weight distribution, combined with a tackifier and softener in predetermined amounts, to enhance solubility, low-melt viscosity, and odor properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional block copolymers are used in pressure-sensitive adhesive compositions, then the adhesive composition can be formulated, but the balance among holding power, tack and adhesive power is unsatisfactory
Solution Approach 1:
The patent changes the molecular weight parameters of the block copolymer components, specifically using a triblock copolymer with weight-average molecular weight of 50,000-200,000 and a diblock copolymer with weight-average molecular weight of 20,000-50,000. It also controls the styrene content (10-40 mass%) and butadiene content (60-90 mass%) to optimize the balance among holding power, tack and adhesive power while maintaining formulation feasibility.
2Ease of operation
If block copolymers are processed into pellets for ease of handling, then transportability is improved, but solubility and odor properties deteriorate
Solution Approach 1:
The patent changes the molecular weight parameters within specific ranges (triblock: 50,000-200,000, diblock: 20,000-50,000) and compositional parameters (styrene: 10-40 mass%, butadiene: 60-90 mass%) to achieve a balance between transportability as pellets and reduced odor properties, while also improving solubility in the adhesive composition.
3Strength
If block copolymer molecular weight is increased to improve holding power, then adhesive strength is improved, but melt viscosity increases making processing difficult
Solution Approach 1:
The patent segments the block copolymer into two distinct components with different molecular weight ranges: a triblock copolymer (50,000-200,000) for holding power and a diblock copolymer (20,000-50,000) for lower viscosity. This segmentation allows each component to contribute its optimal properties to the overall adhesive composition.
Solution Approach 2:
The patent creates a composite adhesive composition by combining two different block copolymer types (triblock and diblock) with complementary properties. The triblock provides strength and holding power, while the diblock contributes to lower melt viscosity and easier processing, achieving a synergistic effect.
Data Source
AI summary
There is provided a crumb of a block copolymer, which is excellent in transportability and, when used for a pressure-sensitive adhesive composition, is capable of forming a pressure-sensitive adhesive composition excellent in solubility, the low-melt viscosity property, the low-odor property, and the balance among these properties. The present invention relates to a crumb of a block copolymer, comprising at least one polymer block comprising a vinyl aromatic hydrocarbon monomer unit as a primary component and at least one polymer block comprising a conjugated diene compound monomer unit as a primary component, having a weight-average molecular weight of 20,000 to 1,000,000, and having a specific surface area, a cumulative pore volume of pores having a pore radius of 1 µm to 100 µm, and an average pore radius that are in respective predetermined ranges.