Water-Dispersed PSA Composition for Low-Temperature Adhesion
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Solution Overview
Problem
Existing water-dispersed pressure-sensitive adhesive (PSA) compositions exhibit insufficient adhesiveness to non-polar adherends such as polyethylene and polypropylene at low temperatures, despite efforts to improve adhesion through the use of tackifying resins and rubber-based components.
Innovation Solution
A water-dispersed PSA composition comprising a (meth)acrylic polymer and a latex that is immiscible with the (meth)acrylic polymer, mixed at a specific weight ratio, along with a tackifier that is miscible with the rubber component but immiscible with the (meth)acrylic polymer, to achieve a storage modulus of 1 MPa or smaller within the range of -15 °C to 25 °C, enhancing adhesiveness at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rubber-based PSA with high modulus of elasticity is used to improve low-temperature adhesion, then the adhesive strength at low temperature is improved, but the storage modulus exceeds 1 MPa in the range of -15°C to 25°C, resulting in insufficient wettability to adherends
Solution Approach 1:
The patent changes the key parameter of storage modulus by controlling the glass transition temperature of the rubber component to be -50°C or lower. This parameter change ensures the storage modulus remains 1 MPa or smaller in the -15°C to 25°C range, achieving both low-temperature adhesion and adequate wettability
Solution Approach 2:
The patent applies local quality by creating a specific rubber phase with distinct properties (glass transition temperature ≤ -50°C) that coexists with the acrylic polymer phase. This localized property adjustment in the rubber component enables the overall composition to achieve the desired storage modulus while maintaining low-temperature adhesive strength
2Adaptability or versatility
If an acrylic PSA is used to achieve versatility, then the versatility and adhesion to polar substrates is improved, but the adhesive strength to non-polar adherends such as polyethylene and polypropylene deteriorates
Solution Approach 1:
The patent creates a composite pressure-sensitive adhesive comprising acrylic polymer and rubber component with immiscible phases. The acrylic phase provides versatility and adhesion to polar substrates, while the rubber phase with glass transition temperature ≤ -50°C provides adhesion to non-polar adherends, achieving broad substrate compatibility
Solution Approach 2:
The patent segments the adhesive system into distinct acrylic and rubber phases that remain immiscible. Each phase contributes different adhesive properties, allowing the composite to adhere to both polar and non-polar substrates simultaneously through phase-specific adhesion mechanisms
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 composition achieves good adhesiveness to non-polar adherends like polyethylene and polypropylene at low temperatures, with improved wettability and adhesive strength, maintaining performance even at -15 °C.
Implementation Method 1
a latex containing a rubber component that is immiscible with the (meth)acrylic polymer
Implementation Method 2
exhibits good adhesiveness to a non-polar adherend at a low temperature... improved wettability
Data Source
Figure 1~2
Figure 3(a)~3(c)
AI summary
The present invention makes a water-dispersed PSA composition capable of forming a PSA that exhibits good adhesiveness to a non-polar adherend such as polyethylene and polypropylene at a low temperature. The water-dispersed PSA composition comprises a (meth)acrylic polymer obtained by polymerizing a monomer composition comprising as a primary component an alkyl (methacrylate having an alkyl group with 1 to 18 carbon atoms, and a latex containing a rubber component that is immiscible with the (meth)acrylic polymer, the (meth)acrylic polymer and the latex being mixed at a weight ratio ((meth)acrylic polymer/rubber latex) within a range of 95/5 to 25/75 based on solid contents; wherein a storage modulus in a range of-15 °C to 25 °C is I MPa or smaller, the storage modulus being determined by a dynamic viscoelastic measurement in which shear strain is applied at a frequency of 1 Hz, the measurement being taken with respect to the water-dispersed PSA composition dried at 100 °C for 3 minutes.